Psych 3420 Prelim 2

What is a scale composite? Provide an example.

- Scale composite in LOTR: filmed the hobbits and elves at separate times - Film at two different times at two different distances, composite them together - E.g.: the formation of the fellowship → filmed the hobbits and Gimli at further distance, then filmed Gandalf, Aragorn, and Legolas at closer distance and composited the footage

Explain why Johnny Lee's demonstration of depth on the Wii is so powerful.

- Motion parallax is very powerful - By moving position of sensor, can track head to create motion parallax & closed-loop display - With head tracking turned on, the TV seems more 3D as if they are reaching into the real world - Only works for one person at a time - Showed an example of open-loop (to make it close loop, you have to use your head) - So you can get a strong sense of depth without moving head or immersing in VR

What is anamorphic art?

- Needs to be viewed at a specific image to look normal, otherwise is stretched/distorted (distorted perspective) - da Vinci drew first known stretched image in 1490s - Portraiture common (e.g. anamorphic skull) - Wide-angle perspective

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

- Often called lazy eye, present in 6% of U.S. population, 1% in Saudi Arabia, and highest in Russian orphanages - Critical period: 1-3 year range - Symptoms: very strong eye dominance, lack of binocular neurons - Causes: asymmetry in eye muscle, asymmetry in optics, prenatal exposure to alcohol - Two forms: 1. Strabismic amblyopia - also called squint misalignment of eyes (one of the eyes doesn't keep up, usually both eyes track object) 2. Anisotropic - one eye out of focus

What are the three primary dimensions of texture? Ware

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

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

- Panum's fusional area is the range of area that you can get a good fused vision. Moving outside of this area, you get double vision (diplopia) and it does not feel comfortable. As you go off axis, the range of acceptable disparities decreases. If you have big enough diplopia (distance is big), you lose the ability to distinguish depth. - Single vision, beyond is double vision, can still have depth - Eccentricity makes the distance larger

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

- Motion parallax is a very powerful cue to depth - Animals that have two eyes on their head- their relative movement is called motion parallax - Move and zoom two images on top of each other- move the foreground image and zoom the background (local 2D transformations) → produces a 3D like image through a strong feeling of relative depth

Bruneleski in 1413 described what primary aspect of linear perspective.

- Parallel lines appear to recede in distance and converge at a single point, creating a vanishing point - Objects in the distance appear smaller

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

- R & G @ 100 halfway on line between R & G = 200 units of light - Varying amount moves closer to B, but need infinite amounts of light to get to 3rd point - Max of R, G, B = 256 each (white) - Maxes of halfway points on line = 512 each - From yellowish green to purple Maximum is 255, so line doesn't reach all the way across triangle

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

-LUV: colors equally discriminable -Coordinates result in more equal size ellipses; similar discrimination ability across chart -CIELab color space (non-linear) is very popular, matched to sensitivity, good for image manipulation, discriminability ellipses -XYZ: can detect small changes easily at bottom of triangle, but not top (sums to 1) -Set of imaginary primaries used by CIE diagram -Enclose visible gamut, can be used to describe color independently from current & future display technologies

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

-Protanopia: absent Red-Sensing Pigment, 1.0% (many confusion lines) -Deuteranopia: absent Green-Sensing Pigment, 1.1% -Tritanopia: absent Blue-Sensing Pigment, 0.001% -The confusion line represents a line of colors that cannot be distinguished by a colorblind person

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)

Because frequencies outside of this range (2 Hz to 55 Hz) increase the chance of optically induced seizures

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

The rays are all parallel but they are coming at you even though you see them as coming straight down, so you see them as roughly equidistant and much further than it actually is so you don't see it as parallel but rather something that is expanding- closer to you at bottom than at top)

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

The dominance of vision over other sense modalities in creating a perception When you are accelerating down the runway they tilt you back- vision says you're going straight but you feel pressure on your back but your vision dominates so that you still believe you are going forward (simulation). In VR, disappearing hand. Dominates other senses Pointing at Field, only 1 eye has finger actually pointing at him (dominant eye) Requires tactile input See as rectangle, and feel as rectangle, even if it is a square Disappearing hand video If I point somewhere and the VR has some area, you will easily adapt to that and follow whatever your vision is seeing

Examples of 2 ocular cues

(1) Binocular disparity: our eyes see the world from slightly different angles (more info to create a single 3D image); difference between projections of the world on the 2 eyes (2) Binocular convergence: looking at a close object causes your eyes to rotate inwards, use degree of rotation to interpret distance

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

(1) Find two colors along a color confusion line for the test in question (i.e protanope vs. deuteranope) (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 and sizes of the stops (4) Option: make a number of lower contrast that will be visible to the subject of the test

Examples of 2 motion cues

(1) Motion parallax: depth cue resulting from motion; as you move, objects closer move farther across field of view than objects in distance; would still get rich depth of information even if you close 1 eye - If I am looking at an object and moving past it, objects farther away move in 1 direction while objects closer move in another direction; moving fast = close (2) Kinetic depth: strong feeling of what it is as soon as it moves (shape from motion)

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

- Categorical colors: easily distinguishable colors Post and Greene (1986) - Experiment on the naming of colors produced on a computer display and shown in a darkened room, 210 different colors in 2 degree patches surrounded by black - Noticed only eight colors plus white were consistently named (small number of colors can be used effectively as category labels) - Pure monitor red was often named orange, true red required a small amount of blue - Easy to confuse colors in same category - For displays, use small # of colors

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?

- "Alter the perceived distance, and thereby, alter the perceived size" - 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. - 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.

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

- A lot of similarities about where people place color boundaries - If a language has 1-2 color names, often black & white - If 3 color names, adds red, 4 color names adds green/yellow - Throughout cultures, certain continuity in color naming 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

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

- Additive: film, projection, any digital media that emits light - Subtractive: hard copy media (painting, photographs)

Benham's top and temporal colors

- Also called color assimilaton - There is a black, white, and gray disk that is rotated - Phenomena where visual system interprets black and white and gray combinations as actual color

Pulfrich phenomenon

- Bw glasses (dim one eye to create appearance of motion in depth) - Advantages: inexpensive, one camera, motion allowed - Disadvantages: motion tied to depth, requires motion/depth choreography (gimmicky)

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

- Closed loop: can interact w/ display by moving head; behavior can change visuals, which can change behavior (loop) and is typical of movement through the real world - Fully dependent on head position - Ex. teacups at disney- can change ride experience based on your actions, aka how fast you spin - Open loop (early simulators): can't interact w/ display; behavior does not change visuals, although visuals may change behavior - Unrelated to movement of the observer - Ex. magic mountain, pirates of the carribean ride, etc- riding multiple times and changing behavior will not change ride experience - Partially closed loop: not linked to natural movement, but does move in proportion to some action by observer - Not linked to natural movement but does move in proportion to some action by the observer

Anaglyph

- Colored glasses → old way to create 3D - Red filter blocks red light, lets blue thru (and vice versa) - Project two images thru filters and gets eyes to see different image → 3d - Technique: film image from 2 points of view in b/w, project one thru one colored film and second thru another, and view thru appropriate glasses - OR: film image from 2 povs in bw, combine two images into single film strip, view with appropriate glasses - Advantages: large audience, static or motion, cheap equipment - Disadvantages: no correct color, ghosting, depth depends on position

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

- DE = uniquely stimulated brain pixels/screen pixels (SP) - VE = USBP/total # of brain pixels - DE never 100% because SP uniformly distributed & BP not

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

- Danger zones in 3d- eyes constantly converging produces headaches - Should: - Limit extended high disparities - Convergence and accommodation → headaches if under 50 -When you are looking at something close, you also accommodate close- accommodation tracks convergence and vice versa. In a VR system, the accommodation system is fixed but the convergence system is not fixed, so convergence depends on disparities so you will accommodate close but you should not do that because creates headaches.

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?

- Detail perspective - When looking down, you will believe that the wall is higher that it actually is because your brain assumes that the bricks are the same size, so you see the smaller bricks as further away - When looking up at the wall from the bottom, you will believe the big bricks are closer than they actually are

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

- Draws viewer into painting & makes them experience same moment as subject - Achieved drama through POV - Begging Man: Places viewer at level of beggar to create visual bond between viewer and subject - Angels in Ceiling: Angels looking down as if they are enjoying the view turns subject into spectators - Christ: Bring's feet right up to viewer, making us vividly aware of his wounds, POV is stark and severe, Pushes spectator closer than we want to be, feeling coldness of death

Relate Emmert's law to the perception of afterimages

- Emmert's law: perceived size proportional to perceived distance (perceived size = k x perceived distance) - Perceived size/perceived distance = k - Afterimages of objects projected onto background perceived as far = larger - Retinal image is constant; visual angle is constant - For objects w/ same retinal size, further object seen as larger

Volumetric

- High speed projection onto moving surface (rotating mirror) or moving LEDs - True 3D, no glasses, full color possible - Disadvantages: requires fast moving surface and precise timing, difficult for large displays, semi-transparent objects

Lenticular lenses

- Holographic image (ex. Image of Beatles that seems to pop out of page) - 3d postcards - Take 2 images —> slice them up —> lenses magnify a little section of the image so that each eye sees different pixel - Advantages and disadvantages** (missed- add from lecture slides) - Parallax barrier: similar

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

- Illusion technique- Snoop Dog/Tupac - Combines 2 images towards audience viewpoint - Uses a large flat sheet of glass as a beam splitter- image from one scene is reflected, other transmitted, and stage lighting is used to selectively illuminate scenes - Audience cannot see glass- illusion

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

- In 3D scatterplots, adding line that connects point to ground plane allows the viewer to estimate position - Halo: used to distinguish objects in the foreground/background that have the same color - Proximity luminance contrast covariance: more distant objects are faded towards the background color; similar to atmospheric depth, but more extreme - Used to enhance 3D scatter plots by dropping a line from each point; without those lines, only 2D judgement of spatial layer is possible

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

- Its dark yellow lol - It requires a reference of white somewhere in the vicinity to be perceived - There is no such thing as an isolated brown light in a dark room

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

- Lines composing image do not converge to a single point when attempted to use vanishing point - Images appeared flat (only occlusion used) - Did not have actual system to establish linear perspective

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

- Luminance: measured amount of visible light coming from some region of space (candelas/m^2) - Lightness: perceived reflectance of a surface - Brightness: perceived amount of light coming from a source

Auto-stereogram

- Means of creating two depth surfaces - Advantages: no equipment - Disadvantages: repeating texture, inappropriate convergence (headaches), no appropriate texture or colors (need repeating pattern)

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

- Shape from shading- we are used to perceiving light coming in from above us (not below) and forming shapes/depth based on this shading assumption - Shadows → depth (ex. Boat which appears to float above water, balls in video game appearing to move just by shadows moving) - If light is coming from above and is brighter on the bottom, it must cast a shadow and look indented - If we assume light is coming from above it tends to look like it is sticking out a bit - We make assumptions about the 3D of the object based on where we think the light source is coming from

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

- Spatial sensitivity: r-g, y-b channels each capable of carrying only ⅓ amount of detail of the b-w channel, so it cannot be used for displaying any kind of fine detail - Stereoscopic depth: very difficult to see stereoscopic depth because it is primarily based on info from luminance channel - Motion sensitivity: if a pattern is equiluminous to its background and set in motion, it appears to move much slower than a black against a white pattern at the same speed - Form: perception of shape is harder, contrast boundaries help with this - All rely on luminance difference, not chromatic difference

How does one make a three-dimensional postcard?

- Stereo-images interlaced in strips - Ridged lenticular lens above interlaced images - Lenticular lens feeds each eye a different image for the 3d effect (because of raised bumps)

Describe the steps for making a random-dot stereogram.

- Take the pixels - For some of them, shift the pixels from left → right - Now, pixels are not aligned relative to upper and lower pixels → depth effect - Move in differential amounts → tilting effect - Ex. 3D image of pixels using red-blue glasses → balls coming off of screen - What do we learn? Monocular edges are not required

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?

- The building will look like a miniature- large objects should move very slowly due to the acceleration rates of gravity and mass - The miniature should be made to fall at a much slower rate to look larger (as if it has more mass than it does) - Relative rate of acceleration

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

- There are three perceptual advantages to having two eyes - Probability summation: If you have two eyes, you have a second chance at detecting something; more sensitivity to spatial frequency Two eyes: probability P of detection by 1 eye Two eyes P(two) = 1 - (1-P)*(1-P) Field of view (wide) If you lose one, you still have one left - Field of View: Most animals do not have eyes on the front of their head, so two eyes gives a wide visual field Ex. horses can see almost all the way around (eyes on the sides of head) - Depth from disparity *Have an extra in case one is lost lol

Passive polarization

- Two films taken at two different positions → two films projected thru polarizers onto silver oxide screens → audience must wear polarized glasses - Advantages: large audiences, motion, color - Disadvantages: expensive screen, ghosting, polarizers reduce intensity - Real3D uses circularly polarized light to produce stereoscopic image projection (very quickly flipping between 2 kinds of polarization)

Stereoscope

- Two photographs of same object/landscape taken at slightly different angles - View together → illusion of depth and 3D - Advantages: no ghosting (no leakage of image from one eye into other) - Disadvantages: static, single viewer, viewing equipment requires - VR glasses are basically a stereoscope - Cross-Eye Technique

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

- We are sensitive to biological motion - Pendulum motion is important - The ratios of different body parts is important - The actual form is not as important; studies made preserving motion but not form

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

- We have an idea of how quickly something should fall based on its size. If it falls quickly, it is perceived as smaller and closer. When filming miniatures, you should film it at a high rate, and then project it at a slower rate in order to make it seem like it falls slower and is therefore a bigger object Requires 10x light F = ma - If you want something to look small, film it in regular time and then display it at a faster rate- tilt shifted with increased motion D = 1/2at^2: falls w/ the square of the time where a = 10m/s^2 1/100 the distance takes 1/10 the time - If something falls across the screen in 1/2 second, have some estimate on distance - Rule of thumb in film industry, speed filming by a rate of square root of desired size/actual size 100:1 ratio of sizes, film 10x faster, slows projection by a factor of 10

Anomalous color naming

- explains vision of colorblind people (e.g. dichromats confuse RG or BY) - Very rare population of people who are colorblind in 1 eye - Lose color and its opposing color, keep other system

Simultaneous color contrast/constancy

- if two colors next to each other, each is tinged with complement of the other - Surround a grey with red and it will look a little green; surround grey with green will look red - This allows you to be color constant (constantly trying to take illumination into judgement) middle of your distribution of color is usually interpreted as white, color is shifted as your system adapts- ex: green shirt under green illumination is perceived as yellow) - Iso-luminance is very bad for design because not a lot of luminance contrast and strong luminance boundary is what makes things easier to read

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

- lambda = a (lambda1) + b (lambda2) + c (lambda3) - If you have a color, can describe in 3 weights, 3D (sometimes negative) - If one of the variables is negative, can add it to other side (add light to original) - By using three projectors, each with different colored lights, (R, G, B), we can create any color in the visible spectrum through the formula C = rR + gG + bB , where r, g, and b are the amounts of the respective color applied. Since we can yield any color by adjusting the amount of each of the three colors, each color represents a dimension needed to span the entire color space.

Color naming

- no reddish green or yellowish blues (activation of one inhibits the other) - We don't have opposing colors, so you wouldn't describe them in a way that is opposing - Does not explain color appearance sufficiently - Can't have reddish greens - There are no yellowish blues - So we cannot combine colors and get any combination

Tritanope

-Absence of blue photoreceptors (.001%) -Absent blue-sensing pigment (very rare)

Deuteranope

-Absence of green photoreceptors (1.1%); missing middle-wave distinguishing cones -Absent green-sensing pigment -Confuse red and greeen

Protanope

-Absence of red photoreceptors (1%); missing long-wave distinguishing cones -Absent red-sensing pigment -Confuse red and blue

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; more reflection -Subtractive (CMYK) color mixture: subtract/absorb part of the light spectrum to produce color; reflects less (only what both colors reflect -Metamers: pair of colors which differ spectrally but yield the same or similar tristimulus values under at least one set of viewing conditions -Metamers w/ paint = subtractive medium -Metamers w/ added light = additive medium

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

-Advantages: 60 Hz looks closer to reality, continuous images, don't need motion blur, gets rid of flicker, higher frame rate leads to smoother motion -Disadvantages: Requires more film and memory, need a system that can pick up that high frame rate, needs to be sensitive to light/film in bright environments

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

-Color matching (trichromatic): for any test color, possible to get mathematically equivalent color by combining 3 primaries -When matching a test color, it can be the case that using three projectors, each with a different colored light, does not yield a match. In this case, we can add amounts of one of the primaries to the test color, until a match is found. Adding to the test color can be seen as subtracting, or using a negative, primary color from the match found -Ex : Test color = rR + gG + bB -Test color + rR = gG + bB ... The rR added to the test color is a negative primary.

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

-Creates an illusion that the hand has disappeared -Try to keep hands still while shown a video of them —> video shows the hands drifting apart so to make up for it, participant subconsciously moves their hands apart -Tries to grab right hand with left once it disappears- doesn't reach far enough because doesn't realize the hands are so far apart —> feels like hand is gone

To what extent is color symbolism universal across the world?

-Not very prevalent -Red: stimulus (negative or positive) -White: purity, light, cleanliness -Blue: expanse, security -Purple is soothing here, but negative connotations in Asia

Dichromat

-Having two types of functioning color receptors, called cone cells, in the eyes (2.1%) -Can match any color they see with a mixture of no more than two pure spectral lights

Why does CIE use 'imaginary' primaries? What is represented by points outside the CIE chart? For CIE questions, you can assume you will have a chart like this printed out for you.

-Imaginary primaries: coordinate axes outside of color space used so all colors can be in terms of positive coordinates -Negative light: when a light must be subtracted to arrive at a particular coordinate locationIf R and G are fixed at 100, what colors can be produced by varying the amount of B?

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

-LUT: digital to analog converters (DACs) -Every time computers gets to a given pixel, has to decide which LEDs will be on it. Uses LUT to decide what to do w/ 3 guns. The smaller the LUT, the faster decisions are made. DACs converts to phosphors/LEDs. -Particular LUT size & particular RGB size. -If each is 10 bits = 10 bits of luminance 8 bits = 24 bits 8 bit LUT = 256 colors 8 bit DACs = 24 bits of color - 2^8 x 2^8 x 2^8 = 2^24 = 16 million possible colors

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

-Interacting with environment -Helmet mounted display- know resolution of display and what's going on- device presenting visual information -Tracking the head- with oculus rift, they mainly use infrared lights on the headset that calculates position based on lights emitted: Acceleration detectors - -Phones - Wii remote records changes rather than absolute position suffers from drift -Interactive input: Input changes depending on the position of the head - corresponding to 3D movement - mixed reality requires some sort of model of the world.

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

-More of an inability to distinguish between colors than not being able to see colors -We are all color blind: it is why color televisions work -We require just 3 colors to create the visible family of colors -Some individuals need just 2 -Some individuals have 3 cones, but are slightly different -Many of the genes involved in color vision on X chromosome (more prevalent in men)

What is the difference between protanomolous and protanopia?

-Protanomolous: 3 color cones (trichromat), but one of the cones is defective (L cones not missing but defective, all reds are viewed weaker in both saturation and brightness) -Protanopia: red-green color blindness (everything appears blue/yellow)

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

-RGB- going to maximum of each creates a cube -For the RGB system, the family of all colors is a cube. ---For example, once the 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 maximum. -Imagine if you have a two-color space (R & G) -Going out one direction, you max out R; if you want to make it brighter, have to go in G direction and maxed out again -Repetitive maxing out forms a cube -Needs to turn a corner to go back into direction of white so that brightest thing is white

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

-Some ideas of symbolism depend on the culture -Originally Euro disney was purple but In Catholic Europe, purple is a symbol of death and crucifixion- In some Middle Eastern cultures purple signifies prostitution- visitors found the purple color to be morbid. Differences across cultures. -Red in China is nationalism, good luck, celebration, joy and fertility, but has different connotations in America of passion, warning, spicy -This is relevant to design of websites because different colors mean different things to different groups -White in western society reflects purity, neutrality, cleanliness, positivity, but in China it is associated with mourning

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

-The lamp follows the rules of biological motion- jumps and returns to ground, bends knees to reduce jerk, moves proportionally to change in direction -Speed is inversely related to curvature, but judged speed appears constant when rule is followed -Smooth (not jerky), minimizes changes in acceleration

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

-Very little overlap in filters, allows you to use trichromatic system (gives you full color) -Let different wavelengths in; different set of 3 colors -Standard anaglyph splits red and blue and try to transmit images where 1 is intended to go into 1 eye (only a little bit of overlap) -Dolby has separate filter for each eye (each eye filters different wavelengths of RGB and each can produce full color) -Two systems produce physically different colors w/ 2 eyes -Dolby creates film with set of colors for 1 eye, and another set for other eye so each eye is seeing a unique image and then eye sees full trichromatic image when you combine the image

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

-Trichromatic color theory: a theory of color matching - not really color appearance -It is not wrong, just insufficient. -Opponent Color Theory: Three opponent systems -Luminsnce = L + M -Red-Green = L - M -Blue-Yellow = S - (L+M) -Color naming, color afterimages, simultaneous color contrast/constancy, anomalous color naming, Benham's top and temporal colors,

Simultaneous Contrast

-Two colors, side by side, interact with one another and change our perception accordingly. Since we rarely see colors in isolation, simultaneous contrast affects our sense of the color that we see. -For example, red and blue flowerbeds in a garden are modified where they border each other: the blue appears green and the red, orange. The real colors are not altered; only our perception of them changes. Simultaneous contrast is most intense when the two colors are complementary colors.

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

-Visual system maintains efficiency by measuring differences in wavelengths being received by our 3 types of cones -3 opponent color channels assigned to our cones: red v. green, blue v. yellow, black v. white -Variances in luminance cause perception of white -Some cones are achromatic (black & white color channels) & more sensitive to changes in brightness, leading to perception of black & white respectively -The perception of white is due to the balanced mixing of two complementary colors of light, like red and cyan, or blue and yellow -Field: -When they are in balance (e.g. blue/yellow and red/green), it looks white -Getting same output

Benhams 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

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 brightest color across media & in the real world; created by not filtering light -TV: white = 256 units of light from R, G, B -Film: white lets in the most light -Real world: white reflects the most light

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?

-YES -Draw a line between 585 and 500 on the curve and choose the point on the line based on the weights (50% = midpoint). Find RGB, by drawing a line from each vertex to edge opposite of it, passing through the point of interest. Estimate the relative weights of R, G and B based on where each line intersects the edge. Then you solve for R + G + B = 1 and then get a fraction. -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 -All RGB values are based on ratios based on point of interest

Colored afterimages

-staring at a color fatigues cells, so cells for opposing color fires - If you look at blue image, image shown after will look yellow - If you look at bright red, it will look green afterwards McCollough effect: neurons adapt - Gives luminance signal so for a while you believe you are seeing color when viewing a black and white image

Provide examples of depth cues used

1. At Only Close Range: Convergence, accomodation, disparity, depth of field 2. At Only Distant Ranges: Atmospheric perspective, acceleration 3. At All Ranges: Familiar sizes, motion parallax (better at close range though), occlusion

Describe the depth cues available in a painting or photograph (when provided).

1. Atmosphere: Points further away obscured by "atmospheric haze" which makes pale/overlayed parts of the image appear farther away 2. Perspective: Objects closer to our perceived vanishing point are farther away 3. Detail: Using less detail on objects farther away as acuity decreases with distance 4. Color: Use of blues, greys, and other darker colors for objects that are farther away, such as mountains 5. Familiar Size: We have knowledge on the sizes of objects, so we can judge relatively the sizes of each object

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

1. Infants at 4 months can differentiate biological vs non-biological movement 2. Point light walkers- can differentiate sex and age (static images provide little info, but moving images with lights on major joints let participants know sex/age by shoulder and hip differences in movement)

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

1. Rye- Monet (French flags in periphery not as precise as those at center, acuity in periphery < fovea 2. Madame Henriot by Renoir (high acuity in face especially eyes, rest of body is not very detailed, almost blending into background- directs gaze to woman's eyes)

Describe a perceptually perfect (i.e., efficient) visual display based on INTENSITY RANGE.

10^10 scotopic, 10^6 photopic, 30,000:1

Describe a perceptually perfect (i.e., efficient) visual display based on VISUAL ACUITY.

100 pixels per degree (i.e. for VR with visual field of 120 degrees per eye, would need 12,000 pixels)

Describe a perceptually perfect (i.e., efficient) visual display based on VISUAL FIELD.

180 degrees, further from periphery needs larger display to convey information

Describe a perceptually perfect (i.e., efficient) visual display based on NUMBER OF INTENSITY LEVELS.

2^8 to 2^10 (8-10 bits)`

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

Basically you take a camera and take the back plate and tilt it so what is on the top and bottom goes out of focus- which is a cue of limited depth of field. This only normally happens when you are very close to something so if you see it much closer, then you see it much smaller- things tend to look like toys. If you speed up the frame rate, it looks even more like little toys.

Metamer

Colors that look the same, but don't have the same spectral distribution (i.e. yellow v. mixture of red/green); physically different but visually identical

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

If we can alter the perceived distance of something → misapplied size constancy There are no depth cues when looking up at the moon so if viewed at the horizon, the moon is viewed as larger because it is seen as further in the horizon (although people think the moon on the horizon is closer, because it looks bigger) Generally, if you see it as further, you see it as larger You typically see cars on the ground closer than they are so you see them as smaller

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

Lab and luv are the two displays that are trying to make every point on the display equally discriminable- coordinate transforms that make all regions equally discriminable- standard XYZ does not have this. - Advantage: better for accurate display calculations Field - New version of space in which equally distant points are equally discriminable - McAdam ellipses are all same size

Examples of 4 pictoral cues

Pictorial cues: (1) Interposition: closer objects cover farther objects (2) Shape from shading: objects appear in front of their shadow; underlying assumption is that light comes from above - (e.g. hard to interpret river because of direction of light; interpretation of depth changes w/ orientation of image) (3) Familiar size: two of the same objects but one is smaller and looks father - (e.g. Leaning Tower of Pisa) (4) Atmospheric perspective: air obscures object to some extent - As distance increases, background becomes bluer w/ atmospheric haze & reduces in contrast as well

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: representing continuously varying map values using a sequence of colors It can display ratios well (make data more visible) Recommends red/green as its best to convey info in studies and yellow/blue for color blind people

McAdam Ellipses

Regions of equal discriminability; how far away to go for different colors

Describe a perceptually perfect (i.e., efficient) visual display based on MOTION.

Related to the flicker rate: optimize frame rate to have better motion, and optimize motion blur for smoother

Spectrum Locus

Represents all colors perceivable to human eye (curved edge of CIE)

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 perceived as being much closer that you anticipated, what will happen to the perceived size?

Rock is intended to look 2 m high → perceived as closer → will actually look smaller to a viewer (they will think part of the size is accounted for in its closeness, and the visual system will make up for this by saying it must be smaller than it is)

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 smile in periphery but looking at it directly reduces shadows from cheekbones, da Vinci provided coarse details around mouth to suggest smile, fine details for less of a smile

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

The opposite side of white (which is in the middle)

What does a tritanopic confusion line represent?

Tritanope: blue-yellow color blindness - Can be distinguished by deuteranope/protanope - The lines that the colors appear to be the same

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 two degrees per second, you have full acuity. Any faster than that, then the faster it goes the lower your acuity gets. Below 2 degrees per second, full acuity. But beyond that, the faster you go, the lower your acuity- allows you to produce motion blur because you tend not to notice.

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?

Very spiky histogram under fluorescent light, but we don't notice, as long as we can get trichromatic signal out of it. Even though its spiky, your three broad frequency channels are enough to integrate over that so that you don't really notice the difference

According to Livingstone, why do equiluminant colors look unusual?

When looking at equiluminant colors, what system activated and can identify a particular object, where system not activated so can't see position/motion --> object and image can look jittery

Describe a perceptually perfect (i.e., efficient) visual display based on COLOR.

Whole CIE, but more color = more phosphors (currently can only make colors inside RGB triangle)

Describe a perceptually perfect (i.e., efficient) visual display based on TEMPORAL ACUITY.

^0 Hx, but 120-240 Hz for faster motion