Psych 3420 Prelim 1, Psych 3420 prelim 2, Psych 3420 Final

fovea

the central focal point in the retina, around which the eye's cones cluster

186. Describe the differences between virtual reality, augmented reality and mixed reality. Give an example of each.

VR- oculus MR- magic leap, hololens AR- google glass

Assimilation

With fine detail, color surrounds can become more similar (that picture with lines of color intersecting)

hyperopia

farsighted eye is too short too little power causes difficulty focusing on near objects, eye strain, fatigue with close work remedies- positive or surgery

What is foveated rendering? What are the advantages over standard rendering?

is a rendering technique which uses an eye tracker integrated with a virtual reality headset to reduce the rendering workload by greatly reducing the image quality in the peripheral vision (outside of the zone gazed by the fovea) reduces rendering workload bc you only render where the fovea is looking and not in the periphery

What is a switching cost - and how does this apply to computers in the classroom

it takes a significant amount of time for the brain to switch from one goal to another, and from one set of rules to another. there is a switching time cost whenever the subject shifts from the letter-recitation task to the number-recitation task, or vice versa every time you switch from one task to another there is a reduction in the amount of information you are encoding.

perceptual learning

knowledge based/top down systems tare important for object identity

Explain why a negative lens helps a myope to see better.

the negative lens diverges the light so that the image is refocused directly on the retina. myopes have a focal point that is located in the front of the retina and the negative lens pushes it back

What is the illusion of competence?

the people who multitask a lot think they are really good at it, but they are worse at focusing on a single task. you are not processing as much information when there are distractions around you

Bruneleski in 1413 described what primary aspect of linear perspective.

Parallel lines appear to recede in distance and converge at single point, creating a vanishing point.

linear vs radial flow

linear- periphery. perceived backwards and forwards motion radical- expanding motion from central point

How does the early visual system compute ratios? Why is this a good thing?

log(center)-log(surround) this is good b/c due to light consistency, our perceived brightness of an object is unchanged despite changes in illumination

What are the conditions that produce the appearance of self-motion for a human observer? What was wrong with the drum studies? How would you design a perceptually 'efficient' automobile simulator if the observer limited his/her direction of view to straight ahead?

4 types of self motion: 1) linear flow in the periphery 2) linear flow in the fovea 3) radial flow in the center of visual field 4) radial flow in the periphery -the drum study only tested linear motion- did not realize the effect of periphery in producing perceived self motion observer had limited view of central region, should have also used peripheral motion. never measured expansive radial motion -have linear movement in the periphery to give a feeling of motion extra: 1) expansive motion in the fovea 2) motion in the periphery expansive flow in periphery and linear flow in central do not work

What are the differences between luminance, lightness, and brightness. (Ware and lectures)

luminance- A measured amount of light coming from some region of space. Measured in candelas per sq. meter. Can be physically measured lightness- Refers to perceived reflectance of a surface. Psychological variable!! brightness- Refers to the perceived amount of light coming form a source. Psychological variable!!

cone sensitivity rbg peaks

446 blue, 543 green, 566 red

To what extent is color symbolism universal across the world?

Across the world, colors can still have similar meanings - i.e red = stimulus (can be negative or positive) - i.e. white = purity, light, freshness - i.e. blue = security - i.e black = death (from europe to New Guinea), wealth in the US - i.e yellow= happy in US, related to pornography in china

How does the visual system factor out the amount and color of the illumination when making lightness decisions? (W)

Adaption: -ability of the eye to adjust to different levels of dark and light -changing sensitivity of receptors and neurons helps factor out overall illumination -adjust overall sensitivity to ambient light level (level of light that exists within the scene) Lateral Inhibition: the capacity of an excited neuron to reduce the activity of its neighbors

Describe a color matching experiment that proves that the entire color space is 3-dimensional (can be described in terms of three variables).

For any test color, it is possible to reach a mathematically equivalent color by combination of three primaries: at*λt = a1*λ1 + a2*λ2 + a3*λ3 If this equation is true, then holds for any test light then the system is three-dimensional (i.e., trichromatic)

What is chromatic aberration and what is its cause? What is an illusion that arises from this property of the eye? (L)

Different wavelengths of light are focused at different points within the eye -failure of lens to focus all colors to the same convergence point Illusory depth effects -ex: superimposed blue text and red text on black background -60% perceive red text as closer -30% perceive blue text s closer 10% perceive both texts at equal position

Why do we see colors on the surface of a CD? (L)

Diffraction: -light is reflected from a surface that has very fine, regular striations, w/ a spacing of the wavelength light -slight bending of light as it passes around the edge of an object -amount of light bending depends on the relative size of the wavelength of light to the size of the opening -optical groves of CD are spaced regularly, therefore the groves generate different colors at different viewing angles

What is astigmatism?

Imperfection in the curvature of cornea or the shape of the eye's lens -Corneal astigmatism - lens isn't smooth and evenly curved and therefore light rays aren't refracted properly (refractive error) -Lenticular astigmatism - shape of lens is distorted Symptoms -distorted images -blurred vision Remedies - corrective lens, refractive surgery prevents light from focusing properly on the retina, so instead of converging at one point light converges at different points

Describe the relationship between stimulus intensity and intensity of perception that Fechner and Stevens found. How does this relate to the monitor gamma? (W)

Fechner found that intensity of perception was the log of stimulus intensity -subjective brightness is nonlinear relating to luminance entering the eye -gamma and Fechner both recognize that luminance and perceived brightness are not linear (response of system to a set of stimuli is not equal to the sum of the response to each individual stimuli) -we are more sensitive to changes in physical intensity at small values of intensity -the encoding of physical intensity is more precise at small intensities that at large intensities (able to discriminate small intensity differences within a shadow region)

The illumination (e.g., daylight versus fluorescent) can have a dramatic effect on the color spectra of objects. According to Livingston (page 97), why can we still identify colors under these conditions?

Fluorescent: causes spikes but we don't notice as long as we still have the 3 broad frequency channels

bits

The basic unit of info in computing and digital communications -smallest unit of data -related to intensity values in image or screen

Explain how to find a complementary color using the CIE diagram. For example, what is complimentary to 600 nanometers. (Ware and lectures)

The complementary wavelength of a color is produced by drawing a line between that color and white and extrapolating to the opposite spectrum locus. Adding a color and its complementary color produces white. Complementary to 600 nm is 485nm

Purkinje shift

The tendency for the peak luminance sensitivity of the human eye to shift toward blue end of the color spectrum (short wavelengths around 500) at low illumination levels. Rods are more sensitive to light and therefore more efficient in dim conditions. Rods are more sensitive to blue colors, therefore blue colors will appear more bright in dim conditions

If we are so sensitive to biological to how people move, how do we create games and animation that look realistic?

motion capture (Avatar)

diopters

Unit of measurement of the optic power of a lens

What is the uncanny valley? Provide a graph (label the axes). Describe the perception at different points along the curve.

Used in reference to the phenomenon whereby a computer-generated figure or humanoid robot bearing a near-identical resemblance to a human being arouses a sense of unease or revulsion in the person viewing it.

Why is accommodation a problem for virtual reality. Why is this not a significant problem for those older than 60?

VR headsets have a fixed focal length, leading younger people to have to accommodate for it. people older than 60 tend to deal with a set accommodation, so their focal length does not change (accommodation decreases and levels off with age). this is not the case for younger users since their accommodation continues to change. in VR, when you converge close you also accommodate close, but the distance of the screen is fixed. this will cause it to look blurred. the stereo system is varying where the object is.

section 508 of the Rehabilitation Act restricts the use of flicker on websites run by federal agencies. Why? What range of frequencies? (Ware and Lectures)

Websites should be designed to avoid causing the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz because otherwise they could cause pattern-induced epilepsy or other medical issues, such as convulsions and vomiting of blood.

A computer screen has the standard three phosphors (RGB). Use the CIE diagram to show the approximate colors that would be produced by the following RGB outputs. What are the xyz coordinates? RGB250 250 0=? RGB125 125 0=? RGB 25 00 125 =? RGB100 00 100=?

XYZ->XY X+Y+Z=1 Z=1-(X+Y) - RGB 250 250 0 = XYZ .45 .45 .1 -halfway between R and G, read off the x and y coords Z = 1 - .45 - .45 -RGB 125 125 0 = XYZ .45 .45 .1 - same as above, you are gonna be in the same place (halfway bw R and G) -RGB 25 00 125 = XYZ .27 .1 .67 -Z = 1 - .27 - .1 - super close to B with R pulling a lil away, 1/6 of the way to R. read off coordinates Since there's no G, it's going to be on the RB axis, more towards B. -RGB 100 00 100 = XYZ .4 .2 .4 Z = 1 - .4 - .2 1) just read off of the axis 2) Z is just 1-x+y

Are natural scenes redundant? Describe 3 forms of statistical redundancy. Why is this important for understanding compression? Describe how the visual system takes advantage of this?

Yes, natural scenes have a lot of redundancy in which two points next to one another are typically highly correlated -they are predictive for humans Statistical redundancy: 1) neighboring points are similar 2) if not similar, there is likely an edge, and the edges are sparse 3) continuity in edges neighboring points are correlated, so it only responds to differences. the next level focuses on edges. the next level combines it SEC- similar, edge, continuity

Is sensitivity to spatial frequency dependent on the temporal frequency of the stimulus? What does this imply about fast motion on displays?

Yes. Visual images on the retina vary in time as well as in space. People have different contrast threshold at different combination of spatial and temporal frequencies. A particular combination of spatial and temporal frequencies is especially potent: striped patterns of a 3 cycles per degree and flicker rates of about 20 Hz are most likely to induce seizures in susceptible individuals. These patterns may cause great visual stress so that may trigger epileptic seizures in viewers. you do not need fine resolution for things that are moving fast on your retina

blindspot

a place in the visual field that corresponds to a lack of light detecting photoreceptor cells on the retina. with no cells to detect light, the corresponding part of the field of vision is invisible. the brain interpolates the blind spot based on surrounding detail and info from the other eye. therefore we typically do not perceive the blind spot

For a 1.5 meter television screen at 1 meter, how many lines are required to be at the highest visible resolution (assume 100 PPD).

first step- draw a triangle. tan(theta) = size/distance resolution = 100 pix/deg theta = tan^-1(size/dist) 40 degrees need 4000 lines, since 100pi/deg * 40deg resolution = 100pix/deg

What is the disappearing hand trick, and how does this relate to visual capture?

visual capture- the dominance of vision over other sense modalities in creating a percept disappearing hand: 1) participants put their hands in a mirage box, and try to hold them still without touching the blue bars, which keep moving in 2) the images of the hands seen seem to move closer and closer together, so participants must move them further and further away from each other 3) this makes the hands end up further apart than they appear without the participants noticing 4) the image of their right hand disappears and they reach across to touch it, but only feel empty table where their hand was This relates to visual capture because the person knows that their arm is there- they see it going in, they feel their right hand on the table. But because it looks like their hand disappeared and they think that they are trying to touch it in the place it should be, they think that their hand actually disappeared because they do not see it there, even though they can feel it there Clarify

Provide an example of a stage in visual processing where there is considerable compression (hint the optic nerve). What is the magnitude of the compression?

we have about ~120mm photoreceptors in one eye (rods and cons) and 1mm fibers in the optic nerv. 120 to 1 compression. this means that there is less clarity in the periphery.

What does it mean when we say that the visual system uses a "sparse" representation?

we only use an amount of neurons necessary to understand what the image is. only use what is necessary

ghosting

when you see one image in an eye that was intended for the other eye

In terms of the power of the lens and cornea, describe the difference between someone near-sighted and far-sighted. Describe how lenses help these people.

cornea produces about 40D, really powerful lenses lens has 10-22D range whole system can range from 50-62D if light is coming in parallel and converging on a point, the distance between the center of the optics and the back of the eye is .02m need 50D just to look at infinity need more power to focus on anything that is closer than that. the extra power depends on how close (10cm = 10D) ^normal eye nearsighted (myopia)- when you are looking at infinity, this person has a lens that focuses things in front of the retina (lens is too powerful). farsighted- focuses back behind the retina. can use the lens to bring it into focus. need more power to focus on closer thing lens- if you have too much power, then you need a negative diopter lens to fix that

Describe the roles that the cornea and lens play in focusing an image.

cornea: has 40D focusing power acts as a window that controls and focuses the entry of light into the eye lens has 10-12D of focusing power changes the focal distance of the eye so it can focus on objects at various distances, allowing sharp images to be formed on the retina

holography

created with a coherent beam. light bouncing off object creates an interference pattern with the reference beam. this interference pattern is then stored

According to Livingstone, why do equiluminant colors look unusual?

The visual system can be broken up into the "What" region and the "Where" region. The What region helps determine form, while the Where determines depth. Equiluminant colors only stimulate the What system, causing images to look flat, float ambiguously, or shift position if only equiluminant colors are used

How can flicker above the critical fusion frequency still have an effect on a human observer?

There are cells in the LGN that respond to higher temporal frequencies than 60 Hz and are more sensitive than human observers to flicker -the signal is therefore available to our visual system, but not our conscious visual system -cells in the visual cortex appear to discard the high-frequency info -the signals can still reach the brain through other non conscious means and cause cognitive deficits and headaches Also Phantom Array -fast moving flickering objects can cause a potted or multicolored blur instead of a continuous blur as if there were multiple objects when your eyes are moving, they are strobing as they are moving around. the faster something moves th

Describe the primary differences between the 'what' and 'where' systems along the visual pathway. (L).

"what" pathway: -object and visual identification and recognition -ventral system -carries info about color -more acuity "where" pathway: -processing the object's spatial location relative to viewer -how you reach for something and how you manipulate something -dorsal system -high contrast sensitivity -faster

If R and G are fixed at 100, what colors can be produced by varying the amount of B?

- R at 100 + G at 100 → halfway on the line between R/G = 200 units of light - Then adding varying amounts → moves you closer towards B - But you need infinite amount of light to get all the way to third point- Max of R,G,B = 256 each (white) - Maxes of halfway points on line = 512 each

What is a scale composite? Provide an example.

- Scale composite: film a scene at two different angles, then composite them together to make them look like they're part of the same shot - i.e. hobbits standing next to elves; hobbits were filmed farther away and then the two scenes were composited together.

191. Describe the difference between 2D, 2.5D and 3D representations. How can Escher's paintings be explained in terms of this difference?

- 2D- flatland. two values are required to determine the position of an element. can see inside and outside the house because you are in the display - 2.5D- 2D image with distances that go to the different places. our representation. cant see both inside the house and outside at the same time. depth cues telling the relative depths of the objects - 3D- our cognitive construction of what we think would happen if we could see everything. we have models of what movement would look like, we make assumptions about what happens in the world. assumptions and models of what would happen if you moved somewhere that you could see them. you cant perceive someone's legs if they are hidden but we have an assumption about what would happen if he were in a position that you could see his legs. - our perception is not 3d- we have a 2d image in front of us - to have a true 3D world you would have to be outside of it - escher- 2D cues that give good 2.5D cues, then you build a 3D model from it but it is hard. local regions look fine but we cant get a good global model of it. no easy solution that allows this 2D information to give a consistent 3D model that works with our assumptions

What are the advantages of filming at 60 Hz or better? How does this improve the appearance over traditional techniques. What are the disadvantages?

- 60 Hz+ gets rid of flicker - Higher frame rate = smoother motion Advantages: -no flicker -smoother motion, better quality -can help have less jitter because images get blurred Disadvantages: -requires more film + memory + storage -need a system that can pick up that frame rate, needs to be sensitive to light/film in bright environments In all cases, motion smoothing (anti-aliasing) is likely to be helpful.

170. Describe three examples of augmented or mixed reality and include an application for each

- Augmented reality (AR)-adds digital elements to a live view often by using the camera on a smartphone. ex: Google glass just puts an image up, it doesnt interact with the world. application- displaying someone's name above their head through AR glasses - Virtual reality (VR)-implies a complete immersion experience that shuts out the physical world. Using VR devices such as HTC Vive, Oculus Rift or Google Cardboard, users can be transported into a number of real-world and imagined environments such as the middle of a squawking penguin colony or even the back of a dragon. application- play a game in a virtual world - mixed reality- combines elements of both AR and VR, real-world and digital objects interact. Ex: magic leap, hololens. you can put a dragon on your desk that hops around your world - if you want to have a meeting with someone in another office, you both put on a headset and interact with each other - medicine- AR systems can be used to superimpose live ultrasound images of internal organs onto the body. Surgeons could conduct robotic surgery form anywhere using telepresence techniques and be protected from the risk of exposure during operations - rehab and physical therapy- can be enhanced by sensory equipment. snow-world can help burn victims reduce pain, reduce anxiety, pain, pain intensity, etc. People who are withdrawing from opiates distract people from their pain - architecture- can explore space inside of a house

Describe an example of how "point of view" was used by Mantegna .

- Ceiling painting of angels looking down turns the subject into the spectators and the spectators into subjects. - makes you feel down low - placing us at ground level at the feet of the subject

Relate Emmert's law to the perception of afterimages

- Emmert's Law: perceived size is proportional to perceived distance. Perceived size = k * perceived distance (Assumes CONSTANT retinal size) - An afterimage appears to grow in size when projected to a further distance

(W) 206. What is FACS theory and how does this relate to Avatars.

- FACS: facial action coding system - measuring/defining groups of facial muscles and their effects on expressions - convey appropriate human emotion in computer avatars

face verification vs face search

- Face verification- what our phones do. tries to verify if your face is trying to open it - Face search- is this person in a database? problems with false matches

168. What is so remarkable about the boy that "clicks" video? What skills did he have?

- He clicks in order to know what is around him. - When he clicks, sound bounces off of the objects around him and he knows where he is and what is in front of him. Kinda like echolocation. - His ears are so sensitive that he can interpret the echos of the clicks

What are categorical colors? How is this related to color confusion? How is this relevant to displays? (Ware)

- If a color is close to an ideal red or an ideal green, it is easier to remember. Colors that are not basic, such as orange or lime green, are not as easy to remember. - confusion between color codes is affected by color categories - in the Kawai studies, subjects took much longer if the chip was surrounded by distracting elements that were of a different color but belonged to the same color category than if the chip was surrounded by distracting elements that were equally distinct according to the sense of a uniform color space but crossed a color category boundary.

How does one make a three-dimensional postcard?

- LENTICULAR LENSES: little lenses on the postcard (make the scratchy sound) - Make a ribbed surface such that either side of the ridge displays part of an image that will go to each eye to make a stereoscopic image

A 50-foot wall is made with large bricks at the top and small bricks at the bottom. What unusual perceptions are you likely to have for objects at the top of the wall looking down? What sorts of perceptions are you likely to have looking up the wall from the bottom? Why?

- Looking down, the wall will seem higher because you see the small bricks as further away, indicating to you that the wall is really high. - Looking up the wall will seem shorter because the bigger blocks that are further away are percieved as closer - Your brain will assume the bricks are the same size so will see the small bricks as further away and the big bricks as closer than they really are

Describe the relation between Panum's fusional area, diplopia and perceived depth.

- Panum's fusional area: area in front of/behind horopter where you still have single vision. - diplopia: double vision. Beyond fusional area you'll experience double vision. You can still have depth perception with some double vision until you reach diplopia threshold - Further out you get qualitative stereopsis, which is double vision and poor relative depth, and further than that you get no depth

What does a tritanopic confusion line represent?

- Tritanopes do not distinguish between colors along a specific direction in color space along this line - The tritanopic confusion line is represented by the lines radiating from the lower part of the CIE Lu'v' UCS diagram. Colors that differ along these lines can still be distinguished by the great majority of color-blind individuals.

What is "display efficacy" (DE)? What is "visual efficacy" (VE)? Why is DE never 100% with current technology? (W. p.56)

- USBP = uniquely stimulated brain pixels = (TBP - redundant brain pixels) - SP = screen pixels - TBP = total number of brain pixels -display efficiency = USBP/SP (how efficiently a display is being used) -visual efficiency = USBP/TBP (the proportion of brain pixels in the screen area that are getting unique information) -DE is never 100% because SP are uniformly distributed and BP are not

How can the rate of falling act as a depth and size cue? How does this relate to filming miniatures?

- Visual gravity cues contribute to perception of absolute distance and size of falling object. - How to make minis look full size? Scene must be filmed at sqrt(desiredsize/actualsize) and projected at normal time to look like time of fall relates to square root of fall height.

(W) 211. What is meant by O'Regan's comment that the world has its own memory? How is that relevant to change blindness?

- We perceive the world to be rich and detailed, not because we have an internal detailed model, but simply because whenever we wish to see a detail we can get it, either by focusing attention on some aspect of the visual image at the current fixation or by moving our eyes to see the detail in some other part of the visual field. - i can presume the world is consistent, so i dont need to remember everything if i assume it will be there the next second. - One of the consequences of the very small amount of information in visual working memory is a phenomenon known as change blindness. Because we remember so little, it is possible to make large changes in a display between one view to the next, and people generally will not notice unless the change is to something they have recently attended. If a change is made while the display is being fixated, we will notice it. But, if the changes are made mid-eye movement, mid-blink, or after a short blanking of the screen, then the change generally will not be seen. - There are many details in the world that we experience that it seems impossible that we have such shallow internal representation of it. - O'Regan says that the world "is its own memory." We perceive the world to be rich and detailed, not because we have an internal detailed model, but simply because whenever we wish to see a detail we can get it, either by focusing attention on some aspect of the visual image at the current fixation or by moving our eyes to see the detail in some other part of the visual field. - i can presume the world is consistent, so i dont need to remember everything if i assume it will be there the next second. change blindness occurs because you assume the world has not changed in between the time we look away and look back, so you dont notice small changes (switching people, etc.). no temporal queues to show that something happened when you blink or look away.

mere exposure effect

- a psychological phenomenon by which people tend to develop a preference for things merely because they are familiar with them - affect is higher than recognition for brief exposure

(W) 213. What are epistemic actions and how do they relate to perception?

- actions intended to help in the discovery of information - info integrated with other recently acquired info in same space - i.e. mouse movement, zooming in, eye movement

What is the difference between additive and subtractive color mixture? Provide an example of each

- additive (RGB) color mixture: add light sources of different wavelengths to produce color; reflects more (Can add colors to get white) - subtractive (CMYK) color mixture: subtract/absorb part of the light spectrum to produce color; reflects less (only what both colors reflect) (subtract colors to get black) - Metamerism is a phenomenon that occurs when colors change when viewed in different light sources. - metamers with paint = subtractive medium - metamers with added light = additive medium CLARIFY

179. What is "anchoring"? Provide an example. Is this an example of subliminal perception?

- anchoring- a cognitive bias in decision making caused by a relevant or irrelevant source of information (the anchor). a number in your visual field for example that you are not aware you saw. - ex: show a picture of a football player with a jersey number. ask how many sacks this person will have next season. if the jersey has a high number, you will pick a higher number of sacks, but if the number is lower you will pick a lower number of sacks. - ex: studio 17 and studio 97 example - like subliminal it bc you are often not aware of seeing the thing - BUT there is no effort to make it below your detection threshold. not below ability to say it was there

motion object tracking

- as many as 4-5 objects can be tracked simultaneously. - even when they disappear or even when all objects disappear from view in an eye blink - parts are difficult to track relative to whole objects - can improve with practice

Describe each system and provide at least one perceptual disadvantage for each of the following three-dimensional display methods. 1. Anaglyph, 2. Video-linked active glasses, 3. Passive polarization 4. Pulfrich pendulum 5. Volumetric 6. Lenticular lenses 7. Stereoscope 8. Auto-stereogram

- autostereograms- a means of creating two depth surfaces. depending on where your eyes are crossed, eyes can perceive an image at slightly different distances. Those weird pictures that you have to cross your eye to see. Advantage: dont need glasses to see them. disadvantage: some people cant overcome the accommodation and see the illusion - anaglyph (colored) - the main way that we created 3D in the 50s. colored lenses. image intended for the left eye in a blue tint, image intended for the right eye in a red tint, the glasses have filters that will filter out the light they are the same color of. 1) film image from two points of view in black and white. 2) combine two images into a single film strip 3) view with appropriate colored glasses - active glasses- heavy, sensor in there that picks up an infared signal that tells the glasses when to flip back and forth. clear vs black in each eye (shutter is closed on lens) very quickly. 1) two films taken at two different positions 2) two views presented in alternate frames 3) audience wears glasses which block one eye and alternate frames advantages- large audiences, motion, color. disadvantages- expensive, precise timing needed, half of the normal intensity - lenticular lenses- those hologram pictures that have things popping out of them. the lenses that cause the ridges on them. 1) stereo images interlaced on strips. cut into strips and interlace 2) ridged lenticular lenses above interlaced images 3) lenticular lens feeds each eye a different image for a 3D effect. - Stereoscope- A stereoscope is composed of two pictures mounted next to each other, and a set of lenses to view the pictures through. Each picture is taken from a slightly different viewpoint that corresponds closely to the spacing of the eyes. The left picture represents what the left eye would see, and likewise for the right picture. When observing the pictures through a special viewer, the pair of two-dimensional pictures merge together into a single three-dimensional photograph. Disadvantage: cannot be used for motion pictures - passive polarization- 1. Two films taken at two different positions 2. Two films projected trough polarizers onto silver oxide screen 3. Audience must wear polarized glasses Advantages- large audiences, motion, color disadvantages- expensive silver oxide screen, ghosting, polarizers reduce intensity - Pulfrich pendulum- In the classic Pulfrich effect experiment, a subject views a pendulum swinging in a plane perpendicular to the observer's line of sight. When a neutral density filter (a darkened lens—typically gray) is placed in front of, say, the right eye, the pendulum seems to take on an elliptical orbit, appearing closer as it swings toward the right and farther as it swings toward the left, so that if it were to theoretically be viewed from above, it would appear to be revolving counterclockwise. Conversely, if the left eye is covered, the pendulum would appear to be revolving clockwise-from-top, appearing closer as it swings toward the left and farther as it swings toward the right. - volumetric- high speed projection onto a moving surface (often rotating mirror) or moving LEDs advantages: true 3D- both stereo and parallax, no glasses needed, full color possible. disadvantages- requires fast moving surface and precise timing with the projection, difficult for large displays, produces semi transparent objects

196. Describe the basic training required for a deep network to learn to classify objects. How does this differ from how most animals learn?

- basic training: start with a network that has a hierarchy of neurons with multiple layers. put in an object, and give it the right answer. use backpropogation to modify the other layers so it gives you a better chance of getting the right answer next time. every time a new thing comes in you get closer to the answer you want. you always have to know the right answer, and supervise the network. - different because we dont have someone always telling us what is the wrong and right answer. we dont have any labels

199. Provide 3 examples of biometrics and 2 issues regarding privacy.

- biometrics- the measurement and statistical analysis of people's physical and behavioral characteristics. mainly used for identification and access control, or for identifying people that are under surveillance - 3 examples: face recognition replacing a boarding pass, fingerprints, iris recognition - 2 issues: facebook facial recognition in pictures- some creepy person can snap a picture of you on the bus and find your information on facebook, placing recognition software in everyday places without people consenting to be tracked- billboards with targeted ads, police have iphone-based facial recognition devices

190. What is negative priming?

- example- there are two letters one behind the other. if asked to read the top one you are slower because you have to inhibit your response to the other. you are in a sense priming the R but negative priming the G, but then you have to read G in the next one and you are slower at it - attention is an inhibition of the other stuff around you - prior exposure to a stimulus unfavorably influences the response to the same stimulus.

Why is Brown an odd color? (Ware and Livingston)

- brown is dark yellow. When colors in the vicinity of yellow and orange yellow are darkened, they turn to shades of brown and olive green -Unlike red, blue, and green, brown requires that there be a reference white somewhere in the vicinity for it to be perceived. Brown appears qualitatively different from orange yellow -There is no such thing as an isolated brown light in a dark room, but when a yellow or yellowish orange is presented with a bright white surround, brown appears -if color sets are being devised for the purposes of color coding—for example, a set of blues, a set of reds, a set of greens, and a set of yellows— in the case of yellows, brown may not be recognized as a set member.

random

- cant show a color on your screen that is outside the RGB triangle, but it still has coordinates - if he says CIE coordinates then he wants x and y

182. What is change blindness? Provide an example. What does this say about the amount of information we code about the world or a stranger that walks up to us?

- change blindness- people detect relatively large changes in the environment. if you look away for a second, and then look back, you often dont notice a small change - example- door study. someone comes by and asks for directions, door comes through, and person changes. people often dont notice it- they think something funny is happening but they dont know what it is - you can replace with people of the same gender and age for the most part, otherwise you will probably notice the change - this says that we categorize the world based on gender and age (most noticeable characteristics). world is coded witha small set of characteristics

169. Provide two examples of sensory substitution that allow the blind to see.

- converting visual to tactile- people are feeling the sensations they get from the world. Wheelchair with camera and back voltage system - converting visual to auditory: - listening to echos (facial visions, clicks) - converting visual image to auditory spectrogram - seeing with your tongue- learning how the electric pulses on your tongue correspond to images in the visual world - artificial eyes- insert artificial retina. not successful in all patients but some are capable of low resolution visual recognition. does not work when the optical nerve is damaged

Provide an example of an artificial spatial cue. Why are these used? (Ware)

- cues that provide information about space that are not based directly on the way information is provided in the normal environment, although the best methods are probably effective because they make use of existing perceptual mechanisms - ex: proximity luminance covariance. Varies color based on distance from viewpoint. More distance objects are faded to become the light or darkness of background. - use halos to enhance occlusion where this is an important depth cue and where overlapping objects have the same color or minimal luminance difference.

(W) 209. What is deep learning? Is this a supervised or an unsupervised learning algorithm?

- deep learning- a hierarchical set of neurons or nodes in which we take an input and feed it through layeres of neurons with intiially random connections, then we use a labeled database to tell it what the right answer is and we change it over time to get it closer to the right answer over time - supervised- you need labels to tell it what is correct and what is not correct. supervised solution - we are unsupervised- we just interact with the world and learn that way

217. What is defensive design? Provide two examples.

- defensive design- trying to stop you from doing something - examples: 1) leaning bar to keep people from sitting or sleeping on benches in the subway 2) spikes on the top of a monument so birds dont sit on it 3) blasting the mosquito noise at night to keep teens away

204. What is the difference between demographics and psychographics? How did Cambridge Analytica take advantage of this?

- demographics- the kind of info like gender, where you are from, age, what did you pay for something, what did you buy -psychographics- personality traits, beliefs, values, behaviors, what makes you tick, psychological info about your personality. allows more prediction about your behavior and what you buy - cambridge analytica-

logan test

- done in 2002 - identix stated that their stats showed an 85.7% correct ID rate during the logan test. would have captured 11-2 of the 19 terrorists if the software was installed in logan airport during 9/11 - problem: we are missing the percentage of normal people that are misclassified. Should always ask the question about the numbers when there are no terrorists. 50% false positive rate

extra

- eigenfaces- principal components of the face (photobook). where is the most popular variance away from the average face (ex: lightness of skin) - systems focused on identifying location of features -3D face recognition using cameras at multiple angles -deep learning- today- sending the image through a neural network using a lot of identifying information. this is where biases come in FINISH

Name three display problems arising from equiluminous (isoluminant) colors. (Wade and Livingston)

- equiluminuos colors- Colours which differ only in hue, not in brightness 1) For colored text on an equiluminous background- in the part of the figure where there is only a chromatic difference between the text and the background, the text becomes very difficult to read 2) If a pattern is created that is equiluminous with its background and contains only chromatic differences, and that pattern is set in motion, something strange occurs. The moving patter appears to move much more slowly that a black against white pattern moving at the same speed. 3) It appears to be impossible, or at least very difficult, to see stereoscopic depth in stereo pairs that differ only in terms of the color channels

184. What is the evidence that subliminal perception exists? What are the conditions under which it might be possible? Under what conditions is it unlikely?

- evidence- the number of experiments where something comes on the screen and gets masked (cant recognize the word), but it then influences the word that they say after. they cant recognize the word but it still has an effect on it. cortine and woods study- - conditions where it is possible- where its above the detection threshold but you can't recgonize it (below recognition threshold) - conditions that are not likely- something below your recognition threshold. if you are attending to something and cannot perceive it then it wont have an effect on you

200. Describe 3 forms of synesthesia. Provide one line of evidence that this is a real perceptual phenomenon.

- music-color- sense of blue - grapheme- color - number form - association of number with color - personification- 12 is grumpy - lexical -> gustatory- gives you a taste when you see the number

183. Describe two ways that identification of an object based on a single feature differs from the identification based on a conjunction of features?

- examples of features: color, orientation, temporal frequency, direction of motion, size, lighting direction, continuity, closure - when you ID an object based on one feature, no matter how many distractors you add you will still be able to pick out the one that is different from the others (parallel search). With a conjunction of features, it is slow and you need to search more when there are more objects. it is a serial search- slows you down - when you want to make a good display, need to get it so that only one feature is different - easier to search and seperate based on one feature rather than two or more 1) serial and slow- if you are looking for something that is red and vertical among verticals and horizontals and red and green things. in search, it is slow if you have to look for a conjunction 2) textures- if i have two regions of things and the only difference between them is a conjunction then its hard to segregate the textures. if they differ by one feature its easy to distinguish 3) illusory conjunctions- if shapes and colors come at you really quickly, you will often see the wrong shapes with the different colors. will get shapes and colors right, but you will assign the shapes to the wrong colors

What is the vergence focus problem? How does this relate to 3D movies and head mounted displays?

- eyes usually converge and accommodate close together - in VR, accommodation dist is fixed, but convergence distance is not fixed (depends on disparities). do not want to accommodate that close, but VR makes you do that -the eyes either converge (when an object is closer) or diverge (when an object is further) when seeing an image. the lenses also focus on the object (accommodation) - with VR, your eyes are always accommodating to the screen strapped on your face, but they're converging to a distance further off. same with movies- they think the image is further back so they are converging, but accommodating for the screen being close - want focus and convergence to be at same place

(W) 214. Describe an example of a 'visual thinking algorithm'.

- finding a math: visual search to start/end. 2. mark in mental math 3. find lines that connect two nodes 4. nark end points in best line 5. repeat from 3 with new start until destination reached 6. store path 7. repeat from 3 to find all paths, avoiding found paths - Visual thinking algorithms are processes executed partly in the brain of a person and partly in a computer. - example: design queries - Example: Visual Queries: problem components are identified that have possible solutions. A pattern is cognitively specified that if found, will contribute to the solution. Depends on if target is preattentively distinct. The whole display is simultaneously analyzed to determine target, and an eye movement confirms target.

Use the projection theory to explain why a dot in depth appears to move when you move your head left or right. Also explain why perceived depth changes with viewing distance.

- if you move your head left to right, that does not change how far out that image is perceived by you - its going to be halfway (or whatever distance) to you no matter where you go or how far you are. percentage change does not change with how far you are JUST DRAW THE PICTURE

185. Be able to identify and give a brief explanation of: Semantic priming, Corteen and Wood experiment, shadowing, the cocktail party effect, illusory conjunctions

- illusory conjunction- when participants combine features of two objects into one object. you usually get the shapes and colors right, but you usually match the wrong color to the shape. attach the wrong things together. Ex: assuming that red goes with heart shape. When you have a lot of features and you ask for a conjunction you get it wrong a lot of the time - cocktail party effect- you are attending to sounds that are going on around you all the time. you hear your name in a crowded room and turn around - semantic priming- you can prime people to recognize a word by priming them with another word. if i flash the word table and the next word is chair, you are faster at identifying the word chair than if i had flashed the word cloud. you can mask the first word so that you dont see if, but that effect still happens. you can not recognize the word but there is still an effect. the word is above your detection threshold but below the recognition threshold. - corteen and wood- they measured galvanic skin response to priming. i shock you to city names, then you do a task where two people are reading things and one is a list of cities, you have a galvanic skin response - shadowing- a task in which a participant repeats aloud a message word for word at the same time that the message is being presented, often when another stimuli is presented in the background. often used in experiments based on attention

Prosopagnosia

- inability to recognize familiar faces - ~2% of the population - patients know that they are looking at a face but they cant say who it belongs to - rely on other non-facial cues for person identification

167. What is synesthesia? Describe one line of evidence that synesthesia is a "real" perceptual phenomenon.

- involuntary and automatic - spatially extended - consistent and generic - people with synesthesia can find a 2 in a field f 5s really fast, showing that they really do see a "color" for each number since this task is quickly completed when the colors are varied FINISH AND CHECK

181. How does one generate a caricature? How is this relevant to prototypes? How might this relate to the difficulty in identifying a face of a different race?

- make a caricature by exaggerating the differences from the average face - faster at recognizing the caricature than the average person- suggests that we recognize people by the variation from the average - distinctive faces are easier to recognize - race: hard to recognize someone from an unfamiliar race because your prototype is inappropriate- you haven't been exposed to enough people of that race. your prototype is an average caucasian face (ex), so all black people are an average away from a black face so they all "look the same"- they deviate from the average in the same direction. with experience, you develop more than one prototype for different races 1) create a prototype 2) extrapolate deviations of the person you are caricaturing 3) exaggerate those features

Binocular disparity is not incorporated into flight simulators. Why? How is motion parallax incorporated?

- motion parallax- when the things in the front move in an opposite direction from the things in the back. gives a little extra depth - Binocular disparity doesn't work at far distances - Motion parallax works for much far distances so they make the background move at a different rate than the closer objects like clouds. - visual scene simulations in flight simulators will only provide monocular cues to depth and distance. In a flight simulator, objects in the distance move more slowly in relation to objects that are more close, creating a cue of depth - build a 3D model and build in parallax based on where you would be

What does work with point light walkers tell us about our perception of biological motion?

- only with a few joints we have a lot of info- how big, gender, how you can recognize someone from a long way away just by how they walk - since subjects can recognize biological motion upon viewing a point light walker, then the similarities between these two stimuli may highlight critical features needed for biological motion recognition.

178. What does the Kunst-Wilson study say about the possibility of subliminal perception? What did they find?

- polygons coming at you. presented polygons really fast and then asked people two kinds of questions- which ones they saw and which ones they liked. the interesting things is that you can be near chance at whether you saw it or not but 60% or so on liking it. - threshold for liking is lower. wills tart to like something even though you dont remember seeing it. once you are sure that you like it then it is almost certainly that you saw it. sure that you saw it doesnt really change anything. unsure of liking means that it is chance that you saw it

176. Prism adaptation is local and active. Explain.

- prism adaptation- when you adapt to upside down glasses after wearing them for some time. There is an aftereffect of adapting to lenses. Lateral or horizontal shifts of the visual field. - local- local to the body part you are using. a single arm can be adapted without the other being adapted. it adapts the body part you are using - active- you have to move your hand to adapt. Must interact with the environment to adapt, just looking at it doesn't allow you to explore the world - smooth adaptation- can adapt to locally discontinuous

Other than binocular disparity, describe two advantages of having two eyes? Use the concept of probability summation.

- probability summation- the principle that there is a greater chance of detecting a visual stimulus with two eyes than with one eye. 1) It gives a wider field of view. For example, humans have a maximum horizontal field of view of approximately 190 degrees with two eyes, approximately 120 degrees of which makes up the binocular field of view (seen by both eyes) flanked by two uniocular fields (seen by only one eye) of approximately 40 degrees. 2) lets say one eye has a 70% chance of seeing something-> 30% chance of missing it. with 2, the chances that they will both miss is 9% or 91% chance of seeing it. With 2, theres a really high probability that you will see things P(at least one eye seeing it) = 1-(1-P1)(1-P2) other: 3) It can give stereopsis in which binocular disparity (or parallax) provided by the two eyes' different positions on the head gives precise depth perception. This also allows a creature to break the camouflage of another creature. 4) It allows the angles of the eyes' lines of sight, relative to each other (vergence), and those lines relative to a particular object (gaze angle) to be determined from the images in the two eyes. These properties are necessary for the third advantage. 5) It allows a creature to see more of, or all of, an object behind an obstacle. This advantage was pointed out by Leonardo da Vinci, who noted that a vertical column closer to the eyes than an object at which a creature is looking might block some of the object from the left eye but that part of the object might be visible to the right eye. 6) It gives binocular summation in which the ability to detect faint objects is enhanced 1) It gives a creature a spare eye in case one is damaged.

180. What is the relationship between prototypes and face recognition?

- prototype- the average positions of the features of the face. depending on how you were brought up you can have a few or many prototypes - we recognize a face by how much it deviates from the prototype, and you are better at identifying a caricature than a face. this shows that high deviation is an even better way to recognize faces -face recognition- we often know a lot about someone but cannot name the person - experiment- gave people a bunch of patterns of dots and asked if they had seen it before - we are really good at extracting prototypes - good at taking variable data and extracting a prototype - when we look at faces, we look at variation away from the prototype. recognition is dependent on your own experience- your prototype is the combo of the people you have experience with

(W) 201. Describe the RSVP method. What does it tell us about the speed of processing?

- rapid serial visual presentation - people can recognize objects in sets of images presented very rapidly - can detect an object accurately given ~10 images/sec, BUT we probably only processed a small amt of info from each image

187. Under what rational definition of subliminal perception can we say that it exists?

- rational definition- something above detection threshold but below recognition threshold. under this circumstances, the effect it has on you is greater than the times that you recognize it

The suns rays appear to diverge as they come through the clouds. Explain this illusion in terms of size and distance.

- rays are parallel, but they are coming right at you but you see them as coming down. expansion is due to the fact that down at level is closer to you then up above in the clouds (far) -The rays are actually just converging parallel lines like railroad tracks going to the horizon -As the rays get farther away, they appear smaller and closer together -The rays closest to the observer appear larger and more spread out, giving the illusion of divergence

210. What is scene gist? How long does it take to recognize the gist?

- scene gist- a first glance of what something is. flash some image up quickly. we are fast at processing the gist of what the scene is. - provides context for perceived object using properties from long-term memory (visual + nonvisual) - can be activated in about 100ms - brain primes for activities we expect in the scene. eye movements needed to find details will be facilitated.

174. If you were to take a vacation using current virtual reality software, what aspects would be missing? What aspects are likely to change in the next 10 years?

- smell, can't climb things. - taste, food - cant surf, cant feel the sun on your skin and the breeze - little forced feedback - to create the social environment of being on a beach is really hard - things to change in 10 years: resolution, bigger visual field, color property, forced feedback

What is Livingstone's theory regarding the origin of the Mona Lisa's elusive smile? (Livingstone)

- smile is in low spatial frequencies, best seen in periphery - seems more like a smile in periphery, but looking at it directly reduces shadows from cheekbones -Da Vinci subtly burred out dark lines to make her expression ambiguous, and depends on which part of the visual field you see her smile. when you look directly at the smile, you can tell a lot of detail so its less clear. when in the periphery, its low resolution and you think she is happy- it fills it in

(W) 207. Describe the role of canonical views in object recognition.

- standard views- we are much faster at recognizing things that are in canonical views than non canonical - canonical view is seeing the hand palm first, non canonical is if it is turned to the side - canonical views as the "front", "side" and "top" views of an object

197. Describe an experiment showing the sensory identification is limited to 7 plus or minus 2 levels.

- the experiment with the blocks that are of different shades of grey. - the experiment where each letter corresponds to a line length. After we have 7 options that we need to memorize we start to fail - pollack and ficks, 6 different acoustic variables that could change. under these conditions the transmitted info was 7.2 bits, which corresponds to about 150 categories that could be identified without error

Describe the relationship between 'shape from shading' and the position of the light source.

- the underlying assumption is that light comes from above. the position of the light source helps us determine the orientation. - shading from the bottom shows it as going out

In the video showing two lamps playing with a ball, why do the lamps look alive and seem to have personality?

- their movements seem biologically accurate - smooth (not jerky), minimize changes in acceleration

Use the CIE diagram to describe the range of colors seen by a dichromat. What is represented by a confusion line?

- things along the confusion line look the same to dicromats -Dichromacy can be defined as a type of color blindness in which the patient either does not have or has weak cone cells in the retina. A patient of dichromacy is unable to recognize any two of these colors: blue, green or red. The reason for this condition is out of the three groups of cone cells in the retina one is usually missing. There are 3 kinds: -Protanopia: Absent Red-Sensing Pigment, 1.0%, patients are unable to spot red color. Also, these patients have difficulty in spotting green color. Singly they are able to easily spot blue and green. However, with a combination of blue and green, they are unable to mark the difference and the color usually appears gray to them. radiate outward from Red corner. -Deuteranopia: Absent Green-Sensing Pigment, 1.1%, patient does not have green cone cells in the retina making him or her unable to spot green color, when a mixture of green and red is presented to them they are unable to spot either one of the colors, but singly a deuteranopia patient can spot red color. goes along the B R line and goes up -Tritanopia: Absent Blue-Sensing Pigment, 0.001%, patient is unable to distinguish between yellow and blue colors (bc no blue cones), -The confusion line represents a line of colors that cannot be distinguished by a colorblind person

What is tilt-shift photography? How does it work? Why does it work? How can a change in film speed improve the effect?

- tilt shift photography- Can be done digitally/ added to film or it can be done by tilting the camera; the center of the image is in focus while the surrounding vignette is blurred. -Utilizes a SHALLOW depth of field (DOF) which works at relatively short distances. -Done to make things look small/miniature. -increasing film speed improves the effect because smaller things move faster

What is the relation between the high threshold for motion and visual acuity? How fast must something move before one loses the ability to resolve spatial detail?

- up to 2 deg per second you have full acuity, any faster than that the faster it goes the lower your acuity -Velocity up, spatial resolution down -Full acuity = velocity of 2 degrees/sec. -If you have short distances and fast frame rates, apparent motion is equivalent to real motion. The limits of temporal and spatial resolution make apparent and real motion indistinguishable.

name your favorite applications of VR that are not gaming

- virtual porn - TV and film, especially in home entertainment - healthcare- employment training for doctors, virtual patients, practice surgical procedures, robot assisted surgeries - VR shopping- virtual malls - Museums- immersive exhibitions, VR tours - Documentaries and Journalism- immersive journalism - live view sports- watch sports as if you're there, can change vantage points - virtual tours- vacationing with a headset - therapy- PTSD treatment, expose themselves to triggers in a safe environment - space exploration- astronaut training, explore and operate in hard to reach places

195. What is the multi-tasking illusion and how does this relate to switching costs

- we feel that we are processing both streams of information but the evidence suggests that we process less total information than if we were processing a single stream - the heaviest multitaskers are the most easily distracted, bad at ignoring irrelevant information, keeping info in their head, and switching from one task to another - multitaskers are really good at switching between tasks, but not when they need to focus on one thing - the feeling that you are really good at multitasking, but then you are really bad at focusing on one thing. - switching cost- A1B2C3, takes a lot of time to switch back and forth. every time you switch between what you are doing there is a cost to switch and you dont pick up as much info

Use projection theory to explain why a 3-D movie can produce a constant depth (when measured in terms of the percentage towards or away from the viewer) independent of where the observer is in the room.

- when you have two eyes looking in different places, you perceive the image as closer - even though people are seeing images in different places, where it is seen is still coming right at you-> image keeps pointing right at you and reaching you no matter where you go, it follows you. picture he drew at session - 3D movies are created by optical illusions, or a combination of cinematography and optics. The majority of 3D films are actually two films playing at the same time; each one has been designed so it's meant to be viewed by either your left eye or your right eye. The 3D glasses you wear filter those images, making sure they're interpreted correctly by your optical sensors (i.e. your eyes). Your eyes and brain naturally combine two images into one; it's the basic principle of sight. When this happens with the two images from a 3D film, you get a layered optical illusion that creates three-dimensional depth.

(W) 205. Describe the basics of Biederman's "geon theory"

- wrote all the objects of the world as 3D components called geons- when we see a new object we try to break it down into geons and make a conclusion about that object based on that - Geon's: describe basic shapes we combine to describe form -Geons: simple 3-D shapes, such as cylinders, rectangular solids, and pyramids-more complex shapes that could be compromised of groups of groups of basic features - Properties of Geon: -view invariance: geons can be identified even at different angles because of invariant properties -discriminability: geons can be discriminated from each other from almost all veiwpoints -may also explain viewpoint variance, and difficulties we have at identifying objects at different angles

188. How does the concept of affordances relate to the design of effective displays? Give three examples.

- you are displaying some information about something. a display is a bar that you need to press to get out the door, how are you supposed to press it? design should give you enough info to know what to do 1) large plate affords pushing 2) handle affords pulling 3) coffee mug handle affords grabbing and drinking

What technologies use additive color mixture? Which use subtractive color mixture?

-Additive color mixing is the kind of mixing you get if you overlap spotlights in a dark room, as illustrated at left. The commonly used additive primary colors are red, green and blue, and if you overlap all three in effectively equal mixture, you get white light as shown at the center (picture). Technologies that use it are TV and computers -Subtractive color mixing is the kind of mixing you get if you illuminate colored filters with white light from behind, as illustrated at left. The commonly used subtractive primary colors are cyan, magenta and yellow, and if you overlap all three in effectively equal mixture, all the light is subtracted giving black. technologies that use it are printers, colored inks, paints

Ware uses the concept of 'Brain Pixels' to describe the efficiency of a display. What is a "Brain Pixel" and how might it be measured? What is an efficient system by his measure? What typically happens to efficiency with increasing display size?

-Brain pixel is the images unit used by the brain to process space. -In modeling the visual efficiency of different screen sizes, we can compute the total number of brain pixels (TBP) stimulated by the display simply by adding up all of the retinal ganglion cells stimulated by a display image. -Uniquely stimulated brain pixels (USBP) USBP = TBP - redundant brain pixels -Display efficiency (DE): ratio of USBP to screen pixels (DE = USBP/SP) -When brain pixel matches the actual screen pixel (DE=1), it's considered efficient (but this is never the case because screen pixels are uniformly distributed and brain pixels are not) -DE usually drops when increasing display size for there are more screen pixels for each brain pixels to handle. -Brain pixel is similar to receptive fields. It is measured by what area of brain is activated by screen pixel. Display efficiency = USBP / SP. Peaks around 35 cm width at 30% efficiency.

Provide two examples that show that color symbolism is not universal. Why is this relevant to the design of websites?

-Example 1: Orange associated with mourning in Egypt, but in Japan/China symbol of courage, love, good health -Example 2: Yellow signifies jealousy, betrayal, weakness in France, but in China associated with pornography -Websites choose colors to evoke certain feelings/symbols associated with the colors

Explain the illusions created by the Hermann Grid and Chevreul/Mach bands in terms of receptive field spacing. Diagrams would be useful here. (W).

-Excited neurons don't trigger neurons lateral to them -Aids in a sharpening affect/perceived contrast

What is forced perspective? How does it apply to the filming of Frodo and Gandalf together on the cart in Lord of the Rings. Why does motion of the camera make this difficult? What is the solution?

-Forced perspective: "Alter the perceived distance, and thereby, alter the perceived size" and vice versa -Forced perspective is a technique which employs optical illusion to make an object appear farther away, closer, larger or smaller than it actually is. It manipulates human visual perception through the use of scaled objects and the correlation between them and the vantage point of the spectator or camera. -in LOTR, characters apparently standing next to each other would be displaced by several feet in depth from the camera. This, in a still shot, makes some characters appear much smaller (for the dwarves and Hobbits) in relation to others. Therefore, Gandalf can look much larger than Frodo, who is supposed to be very short, even though the actual actors are not THAT far away in height. Frodo was actually farther, and you see him closer than he is. Since you see him closer, you see him as smaller -If the camera's point of view is moved, then motion parallax would reveal the true relative positions of the characters in space. Even if the camera is just rotated, its point of view may move accidentally if the camera is not rotated about the correct point. To fix this, you have to keep them on the same axis. As you move the camera, move the actors to prevent motion parallax.

Why does CIE use 'imaginary' primaries? What is represented by points outside the CIE chart?

-Imaginary primaries- coordinate axes outside of color space. primaries outside of the chart. we choose them because negative light is confusing -Used so that all colors can be in terms of positive coordinates. -The CIE diagram uses a set of imaginary primaries defined as XYZ, but the outputs are normalized so that X+Y+Z=1 This creates the XY coordinates of the graph. -points outside of the CIE chart have an imaginary chromaticity that is meaningless and has no realizable color. combinations of the activity of the photoreceptors that are impossible in the real world -Negative light: when a light must be subtracted to arrive at a particular coordinate location

Provide examples of depth cues used 1. At only close range 2. at only distant ranges 3. at all ranges

1) close range- depth of field (only until 10m), disparity (has to do with distance between the eyes) 2) distant-atmospheric perspective 3) all- motion parallax

What is the evidence that color names are not culturally determined. What did Berlin and Kay show about the evolution of color names?

-Kay and Berlin concluded that there exists a kind of evolution of color description. All these cultures, they argued, have a word for black (or dark) and white (or bright). If there's a third color term in the language, it is for red, they found. If there is a fourth, it's for yellow or green (and if a fifth term exists, it covers the other color). Then comes blue. And at the highest stage you have languages, including English, Japanese, and German, that each have a grand total of 11 basic color terms: black, white, gray, red, orange, yellow, green, blue, purple, pink, and brown. 1-2 white/black 3 red 4 green or yellow 5 yellow or green 6 blue 7 brown 8,9,10,11 purple, pink, orange, grey -They showed that language relating the colors evolve in a specific order white/ black and then red

What is the difference between LUV (UVW) and xyz color space?

-LUV coordinates result in more equal size ellipses. Similar discrimination ability across the chart. -xyz color space: xyz sums to 1, can detect small changes easily at the bottom of triangle, but not at top -CIE is not a good representation of how discriminable colors are. UVW was an attempt to make this more apparent

Neurons are the basic unit of computation in the brain. How do neurons communicate with each other? Name one way in which they are similar to transistors, the basic unit of computation in a computer. (W)

-Neurons are the basic circuits of information processing in the brain. -Neurons respond with discrete pulses of electricity. -But, unlike transistors, neurons are connected to hundreds and sometimes thousands of other neurons. -Most neurons are constantly active, emitting pulses of electricity through connections with other cells. -Like the digital circuits of a computer, neurons respond with discrete pulses of electricity.

171.Describe the basic components required for Oculus Rift and the Magic Leap headset. Briefly describe the perceptual experience of each. What problems are you likely to encounter?

-Oculus rift - virtual reality- total world is created for you - Basic components: - head mounted display with two screens with some optics to put it in an optical infinity. - The resolution is approx. at 10-12px per degree. - Track position of the head with infrared sensing - 3D model of the environment - Visual field: 110 - diff/issues: Only see whats been created by comp. Limit in visual field, resolution, more motion sickness than with MR - Magic Leap: - mixed reality - Basic Components - Some sort of infrared of tracking of the head - Visual field: 45 degree - Light comes in the side and bounces back onto your eye, fancy way of making optics .It's called LIGHT FIELD technology - Has to have model of your world - diff/issues: limit in visual field, resolution

Why is pseudocoloring sometimes used for displays? What does Ware recommend (provide two) for the choice of colors? Why can red/green pseudocoloring be a problem?

-Pseudocoloring is the technique of representing continuously varying map values using a sequence of colors. -Two colors that Ware recommends are yellow (which has a very high luminance, almost equal to white) and blue. Red/green pseudocoloring can be a problem to individuals who suffer from protanopia and deuteranopia, both of which cause an inability to discriminate red from green.

Describe and give a brief explanation of each of the following: Kinetic Depth Effect, shape constancy, relative vs. absolute depth cues, Pulfrich effect, horopter,

-Pulfrich effect- small changes in depth in proportion to movement. by putting a filter over one eye, it takes a little more time for the image to get down the optic nerve (seems slightly behind). makes you perceive the object as closer or further back (his example with covering one eye with red lens, it seems like something moving right to left is swinging in an ellipse) advantages- inexpensive, only one camera, motion allowed. disadvantages- motion tied to depth, requires motion/depth choreography -Kinetic Depth effect- to the phenomenon whereby the three-dimensional structural form of an object can be perceived when the object is moving. -shape constancy- when you perceive the "real" shapes of objects regardless of their retinal projections. Ex: you can see the shape of the thing in the world (table) even tho the retinal image is different (we dont see a table as a rectangle but we know it is) horopter-the locus of points in space that have the same disparity as fixation. relative- only telly ou what is in front absolute- gives you a reference of size for something else (miniatures). use familiar size to judge the relative size of something else. cue provides the absolute depth of the object

Provide two examples of art that take advantage of the acuity limitations in the visual periphery. (Livingstone)

-Rue Montergueil, Paris, Festival of June 30, 1878 by Claude Monet - If you quickly glance at the painting, the French flags look okay because they are in the periphery and are unfocused. However, when you focus, you only see misaligned brushstrokes -The rape of the sabine women looks relatively static, because we can see hundreds of details. Seeing so many details is incompatible with the transience of the incident depicted—by the time our eyes move from one act of savagery to another, the scene should have changed. The longer you look, the colder and more frozen the figures in the painting seem- By the time you move your eyes around the painting, the scene should have changed, if it were viewed in real life.

What are the three primary dimensions of texture? (Ware)

-Scale S: the size-1/(spatial frequency) component -Orientation O: the orientation of the cosine component -Contrast C: an amplitude or contrast component

Why doesn't an image normally disappear if I fixate very accurately at one point? What does one have to do to make it disappear?

-Small motions (micro saccades) of the eye create changes in retinal image when the image has high contrast -We need soft edges and blur to make it disappear and somehow control these micro saccades so our brain can actually fixate there is something that is temporally moving on the retina, the only things that are fixed on the retina are the shadows of the retinal blood vessel to make it disappear, fixate on it so it focuses on the retina

What is dithering? Why is it effective perceptually?

-Solution when display has high resolution, but not sufficient intensity levels -creates more perceived intensity levels by mixing pixels from areas of flat color, giving the impression of more colors than are actually available -takes advantage of our eye's tendency to mix colors together (ex: black and white mixed together produces different shades of gray) -creates smoothness and better transitions within the image

177. What is the TVSS? Briefly describe Guarniero's experience with it (see readings).

-Tactile Vision Substitution System - Substitute "eye" (camera) is placed under motor control of blind. The optic signals are transduced into stimuli presented to skin receptors. Matrix of stimulators deliver images to the skin for relay to brain, and blind can be trained to use this info as visual. image is projected onto your back. - at first, you feel it on your back. eventually, it feels like its out there, and you think its on our retina- you see whats in front of you. it feels like its in front of you eventually instead of feeling like its getting bigger on your back - Guarniero said that watching an image move in opposite direction than camera was unsettling, but he adapted so they looked stationary. (think of if you're trying to capture a moving car, but you need to move your camera to get the entire car :p) -Only touch, vision, and TVSS require movement of receptor to explore environment.

What is the advantage of CIElab and CIEluv over standard XYZ color space? What is the difference?

-The CIE XYZ color space is not perceptually uniform. Thus, in 1978, the CIE produced a set of recommendations on the use of two uniform color spaces that are transformations of the XYZ color space. These are called the CIElab and the CIEluv uniform color spaces. They are transformations of the XYZ color space that attempt to be perceptually uniform. -CIElab and CIEluv are uniform color spaces based off of perceptual discrimination -CIEluv: better for specifying large color differences and characterization of color displays -CIElab: 2-6 million discriminable colors available within the gamut of a color monitor, CIE recommends using the CIELAB color space for the characterization of colored surfaces and dyes

For trichromatic displays explain why the full range of colors appears to be a cube in RGB space.

-The RGB color space are the colors that can be displayed on a typical computer monitor (phosphor limitations keep the space quite small) -There are 3 dimensions (RGB) and each has an equal max value, so plotting the possible range of colors on a graph appears to be a cube with red, green, and blue as the axes -For example, once R has maxed out the only way to make it more intense is to add some G or B. White requires that RGB all be at a maximum

Explain Weber's law regarding lightness differences. How much more luminance does a patch need to have to stand out from the background? (W)

-The increase of stimulus necessary to produce an increase of sensation in any sense is not a fixed quantity but depends on the proportion which the increase bears to the immediately preceding stimulus - Limitation: beyond certain brightness, your visual system no longer respond to the increased light. The same thing happens in the opposite limit. -Typically, we are able to detect about a 0.5% change in brightness *Just noticeable difference in intensity is proportional to the intensity

According to opponent color theory what causes the perception of white?

-The perception of white is due to the balanced mixing of two complementary colors of light, like red and cyan, or blue and yellow. - when red and green are balanced you wont see red or green, you will see white. when they are in opponency and one is greater than the other you will see one of the colors

Describe four color phenomena that are explained by opponent color theory that are not explained by trichromatic color theory.

-Trichromatic color theory is a theory of color matching - not really color appearance - There are five things not explained by trichromatic color theory: 1. Color naming- we don't describe colors using terms such as reddish green or bluish yellows -Luminance = L + M -Red-Green = L - M -Blue-Yellow = S - (L + M) 2. Colored afterimages- after staring at an image of certain colors, if you look at a blank sheet of paper you see the opposing colors (temporal effect) 3. Simultaneous color contrast - color constancy- Take a grey and surround it by red, then itll appear green 4. Color naming with those that have anomalous color vision- If you knock out the red, you get rid of the whole red-green system. If you knock out the blue system, you only have red and greens. (color blind in one eye)

What is wrong with the description of some individuals as 'color blind'?

-We are all colorblind- thats why color tv works -Cones only perceive one color and ganglions sum them together -R+G yellow looks the same as true yellow -We require stimulus from three colors to create the colors in CIE that we can see

Use a space time plot to explain why directional blur is sometime introduced into movies or games with fast motion. Why don't we notice the blur?

-When frame rates are low relative to velocity, sampling artifacts become visible -Since acuity drops with retinal velocity, we do not detect detail well and do not notice the blur -the blur removes the artifacts created by the flicker by filling in the gaps in space/direction of motion -For this reason, luring in the direction of motion is able to reduce the sampling artifacts use space on x, time on y. use directional blur because if something is moving slowly, its moving across a small amount of space and a small amount of time. in a time sampled display, as you sample it the next point in time is pretty far out so you get a gap in space.

You are watching a King Kong movie where a 10-story building falls in one second. What are you likely to see? If the original miniature was only 1 meter high but the building was intended to look 36 meters high, what do you do about the film rate?

-You are like to see a fast blurred object. - film rate must speed up by sqrt(intended size/actual size) = 6. film it 6x faster - therefore, when it is shown at normal speed, it seems 6 times slower

What is amblyopia? About what percentage of the population has it? Why is the relevant to designers of 3D displays?

-amblyopia- AKA lazy eye- a vision development disorder in which an eye fails to achieve normal visual acuity, even with prescription eyeglasses or contact lenses, and the other eye is dominant over that one. no binocular vision and one strongly dominant eye -estimated that ~6% of the population has it - 3D is only based on binocular disparity so they cant use that display. no reason to pay for 3D so you wont see it -3D works because of binocular vision- you see two slightly different images that your brain combines into one. 3D lenses may create a viewing condition in which the brain gives attention to the suppressed, amblyopic eye. Unfortunately, this often leads the eye to strain, resulting in dizziness, headaches and nausea. If the brain continues to suppress the eye, the viewer may not experience these symptoms but will fail to see the movie in 3D at all.

What is the difference between the standard anaglyph and Dolby 3D. What are the advantages of Dolby 3D?

-anaglyph (standard blue red 3D glasses): disadvantages: no correct color, ghosting, MAYBE WRONG: depth depends on position. advantages: can have large audiences, static or motion, cheap equipment. -dolby 3D glasses- gets around some of the disadvantages with an anaglyph like technique. each one of the filters is a 3 band notch filter (each getting 3 sets of frequencies) -Steps to create dolby 3D effect: 1) two films taken at two different positions 2) two films projected through polarizers onto silver oxide screen 3) audience has to wear polarized glasses advantages: large audiences, motion color. disadvantages: expensive silver oxide screen, ghosting, polarizers reduce the intensity

What is anamorphic art?

-art that is distorted or stretched, needs to be viewed specially (either at a different angle or reflected onto a curved surface) - i.e. street art

How many colors can I produce with an 8 bit look up table and 6 bit DACs (digital to analog converters)?

-if you have an x bit lookup table, then you have 2^x colors (8 bit lookup table = 2^8 = 256 colors) - if you have a y bit dacs, then you have 2^3y possible colors (6 bit dacs = 2^6 * 2^6 * 2^6 = 2^18 = 262144 possible colors) (3 times bc 3 primaries- RGB) - there are 24 bits of color in DACs -x bit lookup table: 2^x possible colors out of 2^(3*y) colors -y bit DAcs: 2^y*2^y*2^y:

presbyopia

-lens hardens -number of diopters decreases and flexibility of lens is decreases -near point gets further and further with age

Understand the following concepts: Metamer, spectrum locus, McAdam Ellipses, Benhams top, dichromat, protanope, deuteranope, tritanope, simultaneous contrast.

-metameter- perceived matching of colors with different (nonmatching) spectral power distributions. colors that match this way are metameters. physically different but visually identical Spectrum locus- The locus of points representing the chromaticities of spectrally pure stimuli in a chromaticity diagram. -mcadam ellipses-region on a chromaticity diagram which contains all colors which are indistinguishable, to the average human eye, from the color at the center of the ellipse. The contour of the ellipse therefore represents the just noticeable differences of chromaticity -Benham's top- When the disk is spun, arcs of pale color, called Fechner colors or pattern-induced flicker colors (PIFCs), are visible at different places on the disk. Not everyone sees the same colors -dichromat- having two types of functioning color receptors (cones) (2.1%) -Protanope (1%): absence of red photoreceptors -Deuteranope (1.1%): absence of green photoreceptors -Tritanope (.001%): absence of blue photoreceptors -simultaneous contrast- grey, surround it by yellow, it looks blue. Two colors, side by side, interact with one another and change our perception accordingly. The effect of this interaction is called simultaneous contrast. Since we rarely see colors in isolation, simultaneous contrast affects our sense of the color that we see. Simultaneous contrast is most intense when the two colors are complementary colors.

Describe the difference between closed loop, open loop, and partially closed loop displays.

-open loop- Unrelated to movement of the observer (ex: television and movies) -closed loop- Fully dependent on head position- your behavior changes things (you interact with the display by moving your head) (typical of our movement in the real world) - partially closed loop- Not linked to natural movement but does move in proportion to some action by the observer (websites that have parallax based on mouse position- closing loop using the mouse, google maps street view with oculus (bc you can move your head and look around but you are stuck in one location, no motion parallax)) -pirates of the caribbean and magic mountain- open loop. if you take the ride 100 times you don't get a different experience -teacup ride and buzz lightyear shooting game- closed loop

194. What is synesthesia? Describe one line of evidence that synesthesia is a "real" perceptual phenomenon.

-synesthesia- when people sense an added sensory component that is not present in the stimulus. the production of a sense impression relating to one sense or part of the body by stimulation of another sense or part of the body. - evidence- if you put a 2 in a group of 5s, it takes a long time to find the 2. but if you see the 2 as a different color, then they find it much faster. - most people have consistency in the things they see

What is visual capture? Provide an example with simulators and VR.

-visual capture- the dominance of vision over other sense modalities in creating a percept - when you are accelerating down the runway in a simulator they tilt you back. you don't notice that you are tilting back because your eyes show that you are going in a straight line -

In terms of chromaticity and luminance discuss the limitations of the range of possible colors on television, film and the real world. Why is white similar across these media?

-white is created by not filtering out any color, while other colors are created by only filtering out some of the light. white is the brightest with film and in the real world -Lack of brightness and contrast available in today's TV technology -TV standards top out at only about 100 nits, world can be far far more -If the brightest your TV image gets is 100 nits, that means every color that isn't white must be less than 100 nits. - TV: white = 256 units of light from R,G,B - Film: white lets in the most light (you don't filter any light out) and white is the brightest - Real world: white reflects the most light, white is the brightest color.

For virtual reality glasses with a visual field of 180 degrees, how many pixels across are needed to be at the acuity limit. If the display is binocular with 120 degrees in each eye, how many pixels are required for each eye?

1) 180 deg x 100 pix/deg = 18000 pixels 2) 120 deg x 2 x 100 pix/deg = 24000 pixels if each eye can see 120 degrees, need 100pix/deg*120deg=12000 pixels needed for each screen, double for both eyes

Why is skin so hard to model in computer graphics (two reasons).

1) BRDF (Bidirectional Reflection Distribution Function) of skin is much more complicated than other materials -BRDF is important b/c many surfaces have complex reflectance functions and the visual system uses this function to determine material properties -BRDF defines how light is reflected off a surface 2) Uncanny valley - when robots and other facsimiles of humans look and act almost like actual humans, it causes a response of revulsion among human observers 3) we are very knowledgeable about what skin looks like, know the function

Can I match a mixture of 585nm and 500 nm (50% of each) with a color on my computer screen? What would be the RGB output?

1) Draw a line between 585 and 500 on the curve and choose the point on the line based on the weights (50% = midpoint). 2)Find RGB, by drawing a line from each vertex to edge opposite of it, passing through the point of interest. 3)Estimate the relative weights of R, G and B based on where each line intersects the edge. 4)Then you solve for R + G + B = 1 and then get a fraction. 5)Afterwards, you multiply by 255 (or lower value to get a lower intensity but keeping same RGB ratios) -ex. weights G = 4B; R = 0 so 0 + 4B + B = 1; 5B = 1 and then solve 1) go halfway in between the two in the triangle, then convert to RGB 2) draw a line through all the way down 3) decide how much it has to be pulled in each direction 4) 60 to B, 40 to R, intensity on that line is 100 5) 120 to G bc you are a bit above halfway up the green

Rules of Interpretation

1) Most of the visual activity occurs on the boundaries of objects. Representing only the boundaries is often sufficient to convey the meaning of the image 2) Only one object can own a boundary at a time. 3) The boundary is placed at the finest scale (highest spatial frequency). Illusions may occur when there is conflict between highest scale and the image content at lower scales. 4) Perception is 2 1/2 D, Interpretation is 3 D 5) We automatically process the three dimensional structure of an image and have difficulty accessing the two dimensional image

Describe 5 ways to make a spot appear to move.

1) Move the spot (actually) 2) Induced motion (move reference frame) 3) Autokinetic (observe dot without reference) -Phenomenon in which a stationary, small point of light in an otherwise featureless/dark environment appears to move 4) Stroboscopic/ Apparent Motion (flash successive dots) -Short range apparent motion - at short distances and fast frame rates, apparent motion is equivalent to real motion -limits of temporal and spatial resolution make them indistinguishable -stroboscopic effect - visual phenomenon caused by aliasing that occurs when continuous motion is represented by a series of short or instantaneous samples 5) Adapt to motion then observe dot (principle of motion aftereffect) -after viewing a moving visual stimulus for a time with stationary eyes, you fatigue these neurons for this particular motion -when you then look at a stationary object, the stimulus will appear to move in the opposite direction

Describe the three primary stages of perceptual processing according to Ware (W).

1) Parallel processing -extract low level properties of visual scene (feature, orientation, color, texture, etc.) -bottom-up (data-driven) 2)Pattern perception -slow serial processing -top-down processing critical for the formation of objects and patterns pulled out from the feature maps -divide visual field into regions, simple patterns 3)Visual Working memory -only a few objects help at a time -info related to task stored in long-term memory -objects held here by demand of attention

Describe three cues that observers use to discriminate lightness from brightness.

1) Penumbra - blur place of the outer edges of a shadow -helps to understand context of illumination 2) Multiplication across borders - ratios of intensity are maintained along illumination borders -Changes in brightness need to be much larger in order to be perceived 3) Co-planar hypothesis - surfaces in the same place are assumed to have the same illumination w/o other cues that signal a shadow

Name 4 reasons we may want to convert a non-visual data set into a visual data set (W). asked

1) Visualization provides an ability to comprehend huge amounts of data 2) Visualization facilitates understanding of both large-scale and small-scale features of data 3) Visualization facilitates hypothesis testing 4) Visualization helps perceive emergent properties that were not originally anticipated 5)Visualization often enables problems with the data itself to become immediately apparent

173. Describe four ways of physically interacting with a virtual world. Which of these involve force feedback? What is force feedback?

1) dexterous handmaster- depending on how you grab it pulls back (jerk when it feels something). Haptic feedback glove that gives you sensation of interacting with virtual objects. FF 2) flying, gives you resistance based on manuvers. FF 3) treadmill things- as you move the treadmill moves underneath you, or something rotates. makes you feel like you are moving. FF 4) the pad that you have on your hand that has pegs coming out when you touch something. FF 5) socks that make it feel like you are running. socks with the weird peg things. FF - forced feedback- closed loop tactile interaction that provides feedback for the objects that are touched. - because of visual capture the feedback need not be perfect. sometimes called the "haptic feedback"

Describe four applications that use eye tracking in virtual or augmented reality.

1) foveated rendering 2) give avatars realistic eye movements 3) aim your device using your eyes 4) tracking eyes, knowing where there is a sacadde, can make people feel like the room is infinite 5) giving a speech, know if your eyes were tracking the audience well

What are the four main components of virtual reality. Provide an example of each component for a VR tech like the Oculus Rift.

1) head mounted display device presenting visual info- about 110degree resolution (only 10px/deg) 2) method of tracking position of the head (using infared lights on the headsets, read the position and calculate position of head) 3) interactive input- input changes depending on position of the head- corresponding to 3D movement 4) means of interacting with the environment

192. Provide 4 examples that demonstrate that the visual system is making assumptions about what is likely in the environment. Include examples on the relation between 2D and 3D structure.

1) if two lines come together in 2d you assume they come together in 3d 2) if two lines are parallel in 2d then we assume they are parallel in 3d 3) assume 90-degree angles whenever possible when things come in in joints 4)

189. Recognition of a face appears to have a number of stages. Explain. Provide one line of evidence for these stages?

1) recognizing the face as a face- faster than face naming 2) recognizing the face as familiar- pretty fast, yes or no answer 3) retrieving stored biographical knowledge- accessed BEFORE name information 4) retrieving the name of the person (for familiar faces) - evidence: hard to name a face without knowing anything about the person - FFA- fusiform face area

Provide two examples that demonstrate that shadows play a role in the interpretation of objects.

1) shadows can provide a strong cue for the relative height of an object above a plane 2) cast shadows provide spatial info relevant to the layout of objects in space rather than their surface shapes 3) a blurry boundary (penumbra) is telling you about what is causing the change of illumination

Describe two aspects of virtual reality that can make us sick.

1) slow update rate (usually slower than the frame rate) 2) slow frame rate 3) mismatch hypothesis 4) people who have little experience with VR

172. Other than gaming describe five current applications of virtual reality

1) training for space travel 2) military 3) film and journalism 4) healthcare (medical procedures) 5) architecture tours 6) education

216. In terms of visual resolution, how close is the Oculus Rift to visual reality? What resolution is required?

1) visual field- we want a 180-190 degree visual field, oculus has 110 degree field 2) resolution = 12pix/deg, we need 100 (1/10 of the way to reality) 3) ~60hz frame (update dependent on computer) rate, not fast enough for us - know foveated rendering, we need about 100 pix/degree

Describe the four stages of information visualization. What is the role of feedback in these stages (W)

1)Collect and store data 2)Preprocessing to transform data into something easier to manipulate and understand 3) Mapping selected data into a visual representation -display hardware and the graphics algorithms that produce an image on a screen 4)Human perceptual and cognitive system (the perceiver) *Feedback -data gathering (collecting and storing) -exploration (changing the subset that is currently being viewed) -viewing

Describe the five different types of eye-movement and an example of when each is used (or describe the eye-movements that occur as you are running your house trying to catch your cat - or playing tennis).

1)Saccades ->rapid eye movement of the eye b/w fixation points -Ex: scanning a page 2)Smooth pursuit ->eyes closely following a moving object -Ex: following a moving dot -Dynamic acuity - visual acuity with moving objects (acuity falls as velocity increases) 3)Fixational ->maintain visual gaze on a single location -Ex: staring at stationary dot -Microsaccades - eye involuntarily drifts while fixating (visual system needs change in order to continue to see anything) -Tremor - entire body has a natural tremor due to breathing and heart beat 4)Vestibular ocular reflex ->movement in head produces change in eye position to stabilize image on the retina -Ex: stable vision while running 5)Optokinetic nystagmus ->Involuntary movement of eye to follow objects in motion in the visual field -Ex: eye involuntarily jitter to look at a fast car passing through visual field while you are staring at a stationary bench also in the same field

(W) 215. Describe four things that you learned from the Ware text regarding techniques that produce more effective displays.

1. Avoid using gray scale as a method for representing more than 2-4 values. 3. Place symbols representing related information close together. 4. To show relationships between entities, use lines. 5. Make displays as compact as possible to minimize cost of visual switch 6. Anti alias whenever possible especially when you have patterns and line 2. Use more saturated colors when color coding small symbols, thin lines, or other small areas. Use less saturated colors for coding large areas.

Describe the depth cues available in a painting or photograph (when provided). For example, include. 1. Atmosphere 2. Perspective 3. Detail 4. Color 5. Familiar size

1. Further away points are often obscured by "atmospheric haze" which makes pale or overlayed parts of the image appear further away 2. Perspective uses converging parallel lines to convey depth 3. Further away parts of the image should have less detail as acuity decreases with distance so this can make things seem farther away 4. Farther things tend to appear bluer 5. Humans have an idea of how big many things are so including these things can add depth especially if (when combined with other depth cues) they are not as expected, for example portraying something as smaller than expected relative to other things will make it seem farther away

Some rules of 3D interpretation

1. If two lines or edges come together in 2D then they come together in 3D 2. If two lines are parallel in 2 D then they are parallel in 3D 3. Assume 90 degree angles whenever possible

Provide two lines of evidence that we are especially sensitive to biological motion?

1. Infants at four months can differentiate biological versus non-biological movement 2. point light walkers ( coordinated moving dots that simulate biological motion in which each dot represents specific joints of a human performing an action) - can tell sex and age by difference in movement 3. We are extremely sensitive to errors in biological motion- if you dont get it right, you get the uncanny valley effect

Three rules about natural images that apply to art

1. Neighboring points are highly correlated 2. Edge hypothesis: If there is a sudden change in intensity then that change is likely to continue along the discontinuity. 3. Continuity hypothesis - Edges are part of extended surfaces

193. Describe four "rules of design" (according to Donald Norman). Provide an example of each.

1. Visibility and feedback - make signs visible and send information back to user. you should not put text in the same color as the background because then it is not visible. 2. natural mapping - maps controls to real effects (ie. up arrow to go up a page). right arrow on a sign that says turn right. 3. constraints - restrict user interaction. ex: defensive designs. ex: usb sticks can only o in one way and will prevent you for putting it in the wrong way 4. design for error - find errors, make sure errors can be corrected, minimize errors. take into account probable errors that could be made. ex: putting trash cans in between a circle of chairs in belgium. that is not a good design because people will not always throw trash in the right place and it will get all over the chairs. credit card swiper that does not do anything if you swipe the wrong way

(W) 208. Describe two advantages of using animated images over static images

1. can represent concepts like aggression/pushing better than static images 2. can express causality - instead of arrow (which just shows relationship) you can directly see causality 3. easier to detect silhouettes- (can detect the spinning girl better when in motion than if static)

ideal display for a VR system

1.Perfect resolution: 100px per degree BUT you can do less but with foveated rendering. For visual field it is 180/190px per degree 2. Update rates (slow will result in jittery motion) 3. Color: current system is trichormatic. Would be nice to get more phosphorus. More colored led to cover the entire color space 4. 240 is a good frame rate

What type of lens does a virtual reality display require if the display monitors are mounted 10 cm in front of the lens and are intended to be viewed at infinity? What type of lens is required if the observer normally requires -2 diopters of correction?

1/(0.1) = 10D infinity = 1/10D - 10D lens should be -10D If person normally requires -2D of correction, then you need a -8D lens to get to -10

Suppose that you have a near point of 10cm and a far point of 25cm. a. What is your condition? (e.g., hyperope?) b. What is your amplitude of accommodation (the diopter range of the lens)? c. How should this person be corrected? d. After correction where will this person's near point and far point be located?

1/n.p - 1/f.p = 1/.1 - 1/.25 = 10D-4D = 6D 1) myopia- too much power 2) 6D 3) needs a -4D lens 4) after correction, f.p will be infinity (can see clearly). new near point will be 1/(10D-4D) = .17 starting with 50D. to see at 10cm, need 10D (bc .1m), 4D extra power bc .25m away. range is 6D of stretching, thats how much the lens can change its shape. this person is probably in her 40s. total range of a young individual is between 0D and 12D (infinity to 8cm) give a -4D lens, want to be able to see at infinity (since this person is nearsighted. nearpoint is now 1/6, far point is infinity. person is getting presbyotic. the range tells you how much extra. we always want the far point to be out at infinity

ideal iphone

10 degree display needs 1000 pixels need to get more color space higher update rate, as high as possible (240 frames per second is probably good)

What is the gamma of a display? Roughly what is the gamma of your visual system? How does the gamma of your visual system affect the apparent luminance of an intensity ramp?

Gamma of a display- the distribution of intensities on a display. describes the non-linear relationship bw intensity and luminance (changes quickly at first and gradually slows down). takes greater and greater increases in physical intensity for us to detect the change. gamma of visual system- 0.5 output = input^gamma graph is intensity on x, perceived intensity on y as intensity increases, percieved intensity levels off

What is high dynamic range (HDR) imaging. How does this approach increase the apparent range of an image?

HDR imaging- used to reproduce a greater range of luminosity than what is possible with standard imaging. want to expand the low and high intensities photograph the low range and high range separately Captures HDR images and creating images that look HDR on low dynamic range displays. Increases the apparent range of an image by: 1) creating an image with HDR by using multiple exposures or by using an HDR camera 2) display images on HDR display 3) display images on low dynamic range display, but make them appear more HDR through tone mapping

Do a news search for "eye tracking" (e.g., google news). Describe 3 recent applications of eye tracking.

HTC Vive (eye tracking for VR) market research- seeing where people look in ads and commercials web design- knowing where people look to ensure usability of products

Who was Frank Rosenblatt and what is the Perceptron? What can a Perceptron learn and not learn? How is this different from 'deep' learning techniques?

He was a cornell professor in the psych department that invented the perceptron. perceptron- electronic device which was constructed in accordance with biological principles and showed an ability to learn the perceptron can learn linearly separable data but it cant learn the XOR, or most of the object recognition that current systems can do different because deep learning has more layers

Explain the concept of negative primaries in a color matching task.

In color matching, if we choose our primaries to be real lights then the magnitudes will sometimes be required to be negative. Then, you just add that primary to the other side: at*λt + a3*λ3 = a1*λ1 + a2*λ2 If we choose "imaginary primaries", all color matches can use positive primaries.

what is the autokinetic effect

In the dark, without reference, small lights may appear to move (e.g., a single star in the night sky). Sometimes used as a psychological test

(W) 212. What is 'inattentional blindness'?

Inattentional blindness is our inability to register what is going on in our environment unless we are looking for it. We can hold three or four objects in visual working memory if we concentrate hard, but mostly when we interact with displays or just go about our business, we will not be attending to the world that closely.

Why do we see colors in an oily puddle? (Livingstone - 'L')

Interference colors: -colors you see when white light is reflected from 2 parallel surfaces that are very close together -side effect of light slowing down as it passes through different substances -different ranges of thickness produce different ranges of reflected color *able to see the interference colors b/c the thickness of the oil film is in the range of wavelengths of visible light

optokinetic nystagmus

Involuntary movement of eye to follow objects in motion in the visual field -Ex: eye involuntarily jitter to look at a fast car passing through visual field while you are staring at a stationary bench also in the same field

What is the simplest model of surface texture that creates the perception of surface shape from shading? How is this used to shade a sphere with one light source? What are two additional effects that improve how the shading looks? (W)

Lambertian shading (simplest) -surface color will seem the same at any viewing angle -sphere would not be illuminated on side that is not struck by light source -Ex: matte Specular shading -light is directly reflected from a surface -light reflected retains the color of illuminant -Ex: glossy Ambient shading- a gross approximation of multiple reflections from indirect light sources. constant illumination on all surfaces combine all 3 for a mixed (glossy) reflection

What role does lateral inhibition play in lightness constancy?

Lateral inhibition is the capacity of an excited neuron to reduce the activity of neighboring neurons. Lateral inhibition is the first step of edge detection that signals the positions and contrast of edges in the environment. Light Constancy is the perception that the apparent brightness of light and dark surfaces remain more or less the same under different luminance conditions (ratios, rather than actual intensity values, are used for chromatic perception) Lateral inhibition helps distinguish the edges that help to determine the ratios that are needed in order to perceive lightness constancy. When light conditions change, you still receive the same output from receptor cells

Use size/distance theory to explain the moon illusion and the illusion that cars look like toys from the air.

Moon Illusion: -From the ground, you have bad depth cues -> moon looks closer -> moon looks smaller -From the horizon, you have better depth cues -> moon looks farther -> moon looks larger Cars: -Cars look like toys from the air because you have bad depth cues -> they look closer -> they look smaller

Ternus Effect

Neurons in the visual cortex show direction sensitivity, and this selectivity can account for long range apparent motion due to the Ternus Effect, in which blinking dots give the perception of motion if the temporal gap occurs at just the right rate. The perception of motion from left to right or vice versa is perceived. prob not on exam

Are abstract visual representations based only on cultural knowledge? Explain (W)

No Two studies contradict this nominalist position and suggest that people can interpret pictures without cultural training: 1)Deregowski reported studies of people in Zambia who had very little graphic art. Despite this, they were able to match photographs of toy animals with actual toys. 2)Hochberg and Brooks- girl raised in a house with no pictures. If she was exposed to a picture, it was never indicated to her by her parents, and was not told that a picture was a representation of something. When the child was asked to identify objects in line drawings and black-and-white photographs, she was correct in almost all of her answers. *there are universal symbols such as a smile

Describe and provide examples of four pictorial cues, two ocular cues and two motion cues, for the perception of depth.

Pictorial cues: - interposition: closer objects cover farther objects - shading: objects appear in front of their shadow - size: two of the same objects but one is smaller, looks farther - atmospheric perspective: objects at a distance look hazy - familiar size- things around you whose size you know - linear perspective- road that is continuing - detail perspective- things get less detailed as you move away from them Ocular cues: - binocular disparity: our eyes see the world from slightly different angles (more info to create a single 3D image) - binocular convergence: looking at a close object causes your eyes to rotate inwards, use degree of rotation to interpret distance Motion cues: - Motion parallax: as you are moving, objects that are farther away move slower - Kinetic depth: the phenomenon whereby the three-dimensional structural form of an object can be perceived when the object is moving - rate of acceleration- when something falls, it gives you a feeling of the size of something

Before the renaissance, what evidence suggests that artists did not have a solid grasp of linear perspective?

Pre-renaissance art looked flat. Although there were attempts to make art look 3D, because they did not have a grasp of linear perspective, art still looked 2D. When trying to use the vanishing point, none of the lines converged. They only used occulation

203. Describe two experiments with priming that provide insights into object recognition.

Priming: if you identify something, you identify it faster if you see it in the near future 1. people able to recognize objects if primed by visually similar images 2. flashed brief images people couldn't identify and added visual masking afterwards, but still increased chance of recognition even when objects not consciously perceived (priming = dependent on image and not high-level info)

What is a specular reflection? What is a diffuse reflection? How can these two features combine to affect the perception of a material?

Specular - light is reflected at one angle Diffuse - light is reflected at many different angles. get illumination from all over the image specularity- that shiny spot on a ball with a light on it ^this is evidence that it is a shiny material by changing the specularity vs diffusion ratio, you can create different surfaces that can go from highly reflective to matte. can create a range of "shinyness" of things

How does one make an Ishihara color test chart that finds protanopes and distinguishes them from deuteranopes?

Steps to create a color test chart: 1. Find two colors along a color confusion line for the test in question (to find protanopes use two points on a confusion line for protanopes) 2. Using spots, make a number with one color and the background of the other 3. Randomize the intensities (dimmer and brighter) and sizes of the spots (gets rid of edges) 4. Optional: Make a number of lower contrast that will be visible to the subject of the test

175. What are the limits of perceptual adaptation? a. To what sorts of changes can we adapt? b. What adapts? c. How does the Held and Hein (1963) study with kittens relate to prism adaptation?

a. smooth transitions in the visual field. consistent change or expansions and contractions are fine but they must be smooth b. orientation, spatial frequency, light, color, motion. Basically just the felt position of the body c. cat sitting in a cart and cat that walks around, when the walker moves the other moves. The only time they get light is in the contraption. Letting kittens grow up this way makes it so the passive kitten develops perceptual-motor problems, but the waking kitten that actively interacts with the environment is fine. - you can adapt one hand without the other - proprioception: the thing that adapts is the proprioceptive system not the visual system. the position or motion of one body part

202. Describe a perceptually perfect (i.e., efficient) visual display. Include in your discussion. A. Visual field B. Intensity range C. Number of intensity levels D. Visual Acuity and foveated rendering E. frame and update rate F. Color G. Motion

a. visual field: 180 degrees b. intensity range: around 10,000 to 1, c. intensity levels- need about 10 bits, 1000 levels d. visual acuity: 100 pix/deg. need some really small pixels for that. even if you made htat display tho, the rendering is going to take a lot of work to render. solution: foveated rendering (need eye tracking. where you only render where the fovea is looking and blur out periphery e. frame and update rate- - frame rate- 240. HW of how fast successive frames come up ( how many frames your computer is producing and drawing. how fast the other kids can draw) - update rate- ? (something high). speed of the computer, how fast it can render and display new screen (how many times the monitor is refreshing in between. how fast the kids change the pictures) f. color- current system is trichromatic. need to either make the triangle bigger or increase the number of LED colors used to more than the triangle (takes a lot of rendering and processing) g. motion and spatiotemporal burring- fast movement will be jerkey at high frame rates. need really high frame rates, or introduce some spatiotemporal blurring. need it to move fast enough so that we do not need to fully process it.

What is Pepper's Ghost. How it is used to bring deceased rock stars back to life?

an optical illusion that makes it seem like people are there in person 1) animation is projected onto the mirrored surface 2) image is reflected onto the transparent screen, which is angled such that the audience sees image but not the foil used at concerts to bring tupac and michael jackson back to life

Describe the steps for producing anti-aliasing on a computer screen. Why is this done and what does it achieve?

anti aliasing smooths out jagged edges Display has many intensity levels, but not sufficient resolution -combination of foreground and background colors -Reduce "jaggies" that make things look less life-like by adding extra colors and pixels (not just blurring) that is created when image is reconstructed from samples Steps: 1) take high resolution images 2) Blur (remove frequencies before they are aliased) 3)Subsample -shift mean intensity across image -gives appearance that object is moving smoothly across display

what do you need to remember about depth

at a constant visual angle, the thing that is further away appears larger

Be familiar with the following concepts: Autokinetic motion, induced motion, apparent motion, motion aftereffects, persistence, low and high thresholds for motion.

autokinetic motion- illusory movement of a single still object, usually a stationary pinpoint of light used in psychology experiments in dark rooms. As one stares at a fixed point of light, one's eye muscles become fatigued, causing a slight eye movement. induced motion- an illusion of visual perception in which a stationary or a moving object appears to move or to move differently because of other moving objects nearby in the visual field. apparent motion- the appearance of real motion from a sequence of still images. Apparent motion occurs whenever stimuli separated by time and location are actually perceived as a single stimulus moving from one location to another. motion aftereffects-a visual illusion experienced after viewing a moving visual stimulus for a time (tens of milliseconds to minutes) with stationary eyes, and then fixating a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original (physically moving) stimulus. persistence:the optical illusion whereby multiple discrete images blend into a single image in the human mind. believe to be the explanation for motion perception in cinema and animated films. "positive afterimage" (persisting activity in the brain when the retinal photoreceptor cells continue to send neural impulses to the occipital lobe) low and high thresholds for motion: Low: -Lower threshold with reference point -w/o reference: 10-20 minutes of arc/sec -w/ reference: 1-2 minutes of arc/sec High: -How fast can something move and still be visible? -depends on stimulus (up to 2 deg/sec - full acuity; past 2 deg/sec - velocity x highest visible freq. = constant) -fast motion = less acuity

What will be perceived as brighter? A 100 watt lamp that produces most of its energy in the range of 500 to 540 nanometers or a 100 watt lamp that produce most of its energy between 650 and 700?

based on the V lambda curve, humans have better perception of green light (500-540 wavelength) than red light (650-700 wavelength). Our photopic vision peaks in sensitivity around 550 nm of wavelength nits is a perceptual measure of intensity. 100 nits means that no matter the wavelength, that its equal intensity to any other 100 nit lamp (candelas/meters square). nits is a measure of intensity

Explain why Johnny Lee's demonstration of depth on the Wii is so powerful. http://www.youtube.com/watch?v=Jd3-eiid-Uw

because it shows that you can make a very simple head tracking device using only a Wii, and showing that you can create a closed loop system with it that changes depending on where you are

Provide a rough estimate of the spatial frequency of the grating shown on the blackboard (in cycles/deg) and explain how you arrived at this estimate. Approximately, how many lines would there need to be to approach your acuity limit? (also tell us where you are sitting).

box with vertical lines spatial frequency is #lines, #cycles = lines/2 number of degrees is the angle of thumb = number of degrees acuity limit = 50 cycles/deg = 100 lines cycles = 2 lines calc number of degrees # cycles in thumb width is #lines you see *2

lateral inhibition

capacity of an excited neuron to reduce the activity of its neighboring neurons

dynamic acuity

detection and localization of a moving stimulus visual acuity with moving objects (acuity falls as velocity increases)

Describe the differences between efficient, inefficient and restrictive display systems. Do we need all displays to be efficient?

efficient- provides information matched to the limits of the sensory system inefficient- more information than the sensory system can handle restrictive- below the limits of the sensory system not all systems have to be efficient (depends on the relative distance). We just need things to be visible and informative given the distance

Microsaccades

eye involuntarily drifts while fixating (visual system needs change in order to continue to see anything)

Describe four differences between foveal and peripheral processing

foveal processing: 1) uses the cones 2) has more acuity 3) more sensitive to long wavelength light 4) radial flow 5) analysis, encodes, recognizes self-motion peripheral 1) rods 2) more sensitive to light 3) more sensitive to short wavelengths of light 4) responds faster to flicker 5) linear flow 6) location, balance, drives eye movement during self motion

Distinguish between hyperopia, myopia, and astigmatism including the symptoms, causes, and possible remedies of each.

hyperopia: - remedies: positive lenses myopia: -remedies: negative lenses astigmatism: -remedies: get progressive lenses presbyopia: -remedies: get progressive lenses (weak power on top and high power on bottom)

On a graphics terminal you have created the image of a large rock on a field. The rock is intended to look 2 meters high. If the rock is perceived as being much closer than you anticipated, what will happen to the perceived size?

if you think it is closer, it will appear to be smaller

Provide a simple map of the pathways that take visual information from the eye to the brain. Include a discussion of the left and right visual fields and the superior colliculus

informationthat comes through the right visual field goes to the optic chasm to the LGN and then to the left side of the primary visual cortex. information from the left visual field goes to the optic chasm to the LGN to the right side of V1. the paths converge at the optic chasm -light entering eye triggeres rods and cones at the back of the retina -> activate bipolar ganglion cells -> optic nerve-> LGN -> visual cortex

How many "bits" of luminance are available with a display that has only two intensity values (i.e., a monochrome display). How many are needed to produce photographic quality images? What are three factors that have bearing on this number. Will Not Ask

intensity levels = 2^(# of bits) for 2 intensity levels, 1 bit is available need ~10 bits to get photographic quality image 3 factors: 1) screen range 2) image (smooth intensity variations require more bits) 3) screen gamma

Neon color spreading

interpreted in terms of illumination difference

Explain why the dynamic range of a display depends on the amount of stray light. Provide an example.

light emitted from the screen is reflected back, therefore changing luminance ratios. If one screen has a 1000:1 range and 1% of light emitted is reflected back to the screen, the luminance ratio becomes 1010:11 which is about 100:1 1% of 1000 + 1000 : 1%*10 + 10 (this 10 is from the % of the other side of the equation) that percentage means that 10 units of light are coming back

What causes motion sickness? How does this relate to the mismatch hypothesis? Why might motion cause sickness in the first place? Why is one more likely to get sick on a camel as opposed to a horse? Why is a passenger more likely to get sick than a driver even when they are both keeping their eyes on the road

motion sickness caused by active conflict between the vestibular and visual system. mismatch states that there is a difference between them but there is no part that says you must be active mismatch hypothesis- conflict between vision and vestibular system. motion causes sickness because it changes the viscosity in your vesibular system that produces a slight difference- makes your body think that it has been poisoned a person riding a camel feels less oscillation than a horse. A camel has a lower frequency (closer to 1 hz). we are more sensitive to lower frequencies, therefore less sickness on a horse when people have stronger expectation, violations in these expectations makes a person more likely to get sick (ex: passengers in a car have a stronger expectation that the car will maintain the same direction, while the driver is paying more attention and is aware of when changes in direction are coming) passenger is not compensating for the motoin, while the driver is- they see that bump coming and can prepare

vestibuloocular reflex

movement in head produces change in eye position to stabilize image on the retina -Ex: stable vision while running

myopia

nearsighted eye is too long has too much power have difficulty seeing far objects remedies- do not wear glasses for close work, go outdoors, use progressive lenses, negative lens

Are heavy multi-taskers good or bad at multitasking? Explain.

no. last summer Nass and two colleagues published a study that found that self-described multitaskers performed much worse on cognitive and memory tasks that involved distraction than did people who said they preferred to focus on single tasks. Nass says he was surprised at the result: He had expected the multitaskers to perform better on at least some elements of the test. But no. The study was yet another piece of evidence for the unwisdom of multitasking. multitaskers cant focus on one thing, but they are good at multitasking, and they cant help but doing it

Under dim conditions (e.g., finding a star at night), it can be useful to look two or three degrees off the target. Why?

only the photoreceptor rods work well under dim conditions. based on the photoreceptor density around the retina, theres no rods in the center of the visual field. about 2-3 degrees from the center, a few rods come out

mach bands

optical illusion that exaggerates the contrast between the edges of slightly differing shades of grey

visual cortex

part of the cerebral cortext responsible for processing visual info

blindsight

people who are cortically blind due to lesions in their primary visual cortex, and are still able to respond to visual stimuli that they do not consciously see

What is presbyopia? Can you avoid it? What does this do to the near and far points?

presbyopia- when the lens hardens with age, causing the gradual loss of your eyes' ability to focus on nearby objects you cannot avoid it typical solution is to get bifocals no known way to avoid it the near and far points get closer and closer together

198. You have been asked to design a display to monitor racecars on a race track. The display should provide an aerial view of the track and allow the observer to quickly identify each of the 8 racecars, provide a cue as to the amount of fuel left and warn the observer when the fuel in any of the cars is critically low. Discuss the perceptual problems involved in designing such a display and a possible solution.

probably wont ask - make up a solution and think about the problems it could have. - want to convert this into a serial search. - when you want to track a lot of things, you want to convert it so that you only have to be looking at one thing. - want to seperate out who is low on fuel - if racecars are different colors its going to be hard to see which one is flashing - fuel - think about questions where conjunctions are problems- always want to convert it to something where you do not have to look at multiple things

What is the difference between protanomolous and protanopia?

protanomolous- a reduced sensitivity to red light (all reds are viewed weaker in both saturation and brightness) because cones are defective or weaker protanopia- when long-wavelength cones (L-cones) are completely missing

Luminance vs. radiance

radiance- a measure of how much physical light is coming off something (measured in watts) luminance- measured in nit (candelas/meters square), measurement of response to light (takes into account our sensitivity to light brightness- percieved

Roughly, for a single image, what is the range of intensities found in the real world, modern LCD televisions and hard copy?

real world- ~500 to 1 LCD: ~1000 to 1 (can go up to 5000) Hard copy- 30 to 1 depends on stray light

Plot the relationship between scotopic and photopic spectral sensitivity and use this plot to explain the Purkinje shift and why red light or red goggles are often used under scotopic conditions.

red goggles are used under scotopic conditions because acuity tends to be low since the cones are under-stimulated in these conditions. the red can help users activate the cones and increase acuity. dont want to saturrate the rods. but want cones to be activated he red color appears dark under dim conditions given the fact the rods are less sensitive to long-wavelength light. For this reason, the red does not saturate the rods scotopic- stimuli of 105nm are percieved as brigher than other stimuli (nighttime) photopic- stimuli of 555nm are percieved as brighter (daytime) if you are under bright light and move to dimmer light, that saturates rods used in photopic vision making it harder to switch from day to night

lateral geniculate nucleus (LGN)

relay center in the thalmus for the visual pathway. gets major sensory input from the retina main central connection b/w the optic nerve and the occipital lobe in the cortex

saccades versus smooth movements

saccades- rapid eye movements b/w fixation points (ex: reading on a page) smooth pursuit- closely following a moving dot

What is saccadic suppression? How does this help with foveated rendering? How can the loss in sensitivity be used to increase the size of a virtual room?

saccadic suppression- happens when you blink or have sudden eye movements, and the brain blocks visual processing in those moments. acuity drops. gets rid of the blur helps with foveated rendering by allowing for delays in updates during the suppressions, only increase resolution when the person looks at it increases room size by moving the room whenever you saccadde, if you want to walk straight you actually have to walk in a circle

Explain the contrast sensitivity function under scotopic, mesopic and photopic conditions.

same thing as the above one

Describe 2 similarities and 2 differences between the processing of objects along the visual pathway and the processing of objects by deep networks

similarities: 1) they are using a hierarchical nature and multiple layers that have difference receptive fields, and they get more complicated as you move up through the system 2)the kinds of receptive fields they learn is very similar to the brain (learning similar kinds of receptive fields) differences: 1) the way they learn is different- deep networks require huge datasets of labeled data. the visual pathway does not learn on labeled data 2) the visual system has massive feedback, and thats involved while you are processing the information. you use feedback to train the deep network, but after training it does not get and incorporate feedback

Why are sinewaves often used when describing a linear system?

sine wave comes in, sine wave comes out all i need to do is measure one threshold and from that threshold it tells me how much of that frequency gets passed. gives a simple description of sensitivity only need one number to understand it

How does one measure the contrast sensitivity function (CSF) of a human observer? Describe the contrast sensitivity function differences in adults and 3 month olds. What does this imply for information presented to children on a display?

spatial frequency(x-axis) -level of detail present in a stimulus per degree of visual angle contrast threshold(y-axis) -minimum contrast that is able to be detected Images with increasing spatial frequency eventually leads to decreasing contrast sensitivity (1/threshold) measure it by the Method of Adjustment - give someone a grating and adjust until they can no longer see the pattern -Very sensitive around 4 cycles/degree -sensitivity to higher spatial frequencies is reduced with age -infants have low contrast sensitivity photopic peaks around 5 cycles/deg as you age, you increase the curve there is fine detail that younger people will not pick up because they do not have the acuity to pick it up

Describe the difference between supervised an unsupervised learning.

supervised learning- we have prior knowledge of what the output values for our samples should be (labeled data). unsupervised- does not have labeled outputs, so its goal is to infer the natural structure present within a set of data points

Describe the steps for making a random-dot stereogram.

take a couple of images that are random and scattered (same pixels). for one of them, you take some of the pixels and shift them left or right. this creates a disparity in alignment. the slight difference gives you the impression that something is popping out.

The famous blue and black (or white and gold) dress is seen differently by different people. Why? Wont Ask

the co-planar hypothesis- for a given surface, an observer must decide how much of the luminance is due to illumination and how much is due to reflection. thus, brightness (perceived illumination) changes the interpretation of the reflection (perceived lightness). some people believe the dress is under bright light, making them perceive it as blue and black. Others think that the dress is under blue-ish illumination, therefore thinking the dress is gold and white.

V lambda curve

the curve mapping the luminous efficiency wave over length for an average human visual system Scotopic peak ~505 Photopic peak ~555

focal length

the distance between the center of a lens or curved mirror and its focus. distance over which initially collimated rays are brought to a focus

What is cortical magnification? How does this relate to the eye chart of Anstis with letters of varying sizes as a function of eccentricity? (W)

the number of neurons in the visual cortex responsible for processing the visual stimulus of a given size varies as a function of the location of the stimulus in the visual field (Variation in acuity with distance from fovea) -Acuity falls off rapidly with distance from fovea -Half of neurons are processing signals from central 10 deg (makes up only 3% of entire visual field) Chart of Anstis -eye focused @ center can see small letters clearly and can see large letters b/c less neurons are necessary to process the larger stimulus in periphery -eyes focused on outer letters cannot see small letters in periphery b/c not enough neurons are available to process the small letters

receptive field

the region of the sensory surface that, when stimulated, causes a change in the firing rate of that neuron

the oblique effect

the relative deficiency in perceptual performance for oblique contours as compared to the performance for horizontal or vertical contours

What does the CSF say about the differences between the visual system of the infant and the adult?

the visual system of the infant has less contrast (lower curve) and the adult has high contrast. to test you reduce the contrast until you cant see it

Why would late night stores blast 17,000 hertz tones?

they dont want teens hanging out outside, and younger people are more sensitive to that frequency. our sensitivity decreases as we age, and it is painful to hear those noises

Describe three recommendations for children to reduce their chance of getting high myopia? What has happens to the eyes of those that develop high myopia? Is myopia inherited or is it entirely environmental?

three recommendations to reduce chances of myopia: 1) get progressive lenses 2) do not wear glasses for close work 3) go outside The eyes of those that develop high myopia have to continue to grow backward because the close image is focused behind the eye so it keeps growing to accommodate for that myopia is not necessarily inherited. it is not entirely environmental, but there is evidence that: 1) Over a two year period, myopia (measured by increase in diopters -lens power) increases more for those using single lens corrective glasses rather than progressive lenses 2) Correlational data shows that myopic children spend on average 3.7 more hours per week indoors (may be due to lack of sufficient bright light indoors)

Calculate the visual angle of your thumb at arms length, your big toe standing up and the moon. Show your calculations.

thumb is 2.1 cm wide arm length is 60cm inverse tan (2.1/60)= 2 degrees measure number of thumblengths across * 2deg. tells you the visual angle if he gives the lines image, the # of cycles is lines/degree. f

Provide a brief explanation of the Cornsweet illusion (W and L)

two areas that physically have the same lightness can be made to look different by having an edge b/w them. Central line creates the impression that one side is darker than the other -The center/surround organization of the cells in our visual system makes us more sensitive to the light-to-dark transition at the middle than to the gradual changes of exactly the same magnitude on either side of this discontinuity Lateral inhibition -the more active brain cells tone down the sensitivity of the ones next to it -amplifies signal on one side of boundary while diminishing the signal on the other side (more contrast is perceived) This effect is often used by painters to make objects more clearly distinct by enhancing edge contrast, given the limited dynamic range of paint.

ganglion cell

type of neuron located near the inner surface (ganglion cell layer) of the retina of the eye receives visual input from the photocell receptors via two intermediate neurons (bipolar cells and retina amacrine cells)

troland

unit of conventional retinal illuminance 1 candelas/meter^2 seen through a 1mm^2 pupil candela -candela= unit of measure for illumination of surface

What is the relation between lens flare and perceived brightness. Why does this work?

unlikely to ask when a light source gets bright it saturates the system. if it flares out, that is evidence that it is a very bright source. adding flaring to an image, you can make it look brighter without making it brighter

What is the Hermann grid and what is the current explanation?

white lines surrounded by dark squares you dont see a grey dot when you look directly at the intersection of the lines, but you do see grey ones in the periphery receptive fields in the central fovea are much small than in the periphery, therefore there is less lateral inhibition in the fovea Lateral inhibition b/w the center and surround of the receptive field the receptive fields in the periphery that lie at the intersections of the have more light falling on its inhibitory surround visual field is excited by the center and inhibited by the surround. center has more inhibition in it than the center areas. that means that the center is dimmer and gets more inhibited.