Psych 3420 prelim 2

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.

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

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

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

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

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.

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

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

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.

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.

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

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

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

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.

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

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

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

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.

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.

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

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

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

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.

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

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

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

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

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

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

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

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

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:

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

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.

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

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 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

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

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

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

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

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)

Neon color spreading

interpreted in terms of illumination difference

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

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

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.

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

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

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

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.

Assimilation

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

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

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

what do you need to remember about depth

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

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

holography

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

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!!

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

motion capture (Avatar)

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

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.

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

ghosting

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