Chapter 5-the Perception Of Color Flashcards Preview

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Flashcards in Chapter 5-the Perception Of Color Deck (53):
1

Color descriptions use how many attributes and what are they

3; hue, brightness, saturation

2

Hue

"Color"; chromatic aspect of light

3

Saturation

Amount of hue present in light; how deep of a color, how pure it is; the less saturated it is the more white it is

4

Brightness

Amount of light, less of any wavelength changes it to blacker; black-white achromatic axis

5

How many axes

2; red vs green and blue vs yellow

6

RBG

Different color space to define wavelength present

7

Subtractive color mixing

Mixture of pigments; if pigment a and b mix, some of the light shining on the surface will be subtracted by a and some by b. The remainder contributes to the perception of color. See in paining, mixing color

8

When you subtract all wavelengths you see what color

You get black

9

White light has what wavelength color

All colors

10

Mixing blue and yellow make green-how

High pass filter for yellow, band pass filter for blue, the ones that are the same make green

11

Color printer cartridge has what colors

MCY (magenta, cyan, yellow); subtractive

12

Computer screen has what wavelengths

Red, green, blue; additive

13

Additive color mixing

A mixture of lights; if a and b are both reflected from a surface to the eye, in the perception of color, the effects of those two lights add together

14

When all the wavelengths are added together, what color
Or when just red, blue and green added

White

15

S cones

Detect short wavelengths (420-ish), blue

16

M cones

Detect medium wavelengths (535-ish) green

17

L cones detect

Long wavelengths (565-ish) red

18

Cone photoreceptors aren't called by the color because

They absorb all colors, just more sensitive to some rather than others

19

Problem of univariance

Infinite set of different wavelength intensity combinations can elicit exactly the same response from a single type of photoreceptor

20

According to the problem of univariance, one type of photoreceptor ___ detect color discriminations based on wavelength

Cannot

21

With univariance, don't know what stimulated, just how to ____

Respond

22

Photopic

Light intensities that are bright enough to stimulate the cone receptors and bright enough to saturate the rod receptors

23

Scotopic

Light intensities that are bright enough to to simulate rods but too dim to stimulate cones

24

With three cone types, we can tel the ____ amount of different between individual lights of different wavelengths

Relative

25

Under Photopic conditions, what cones are active

S, m and l

26

Trichromacy (young helmholtz theory)

The color of any light is defined in our visual system by the relationships of the outputs of three receptor types; relative outputs of 3 receptor types, how strongly 1 responds in relation to the others

27

Additive mixture uses what material

Metamers

28

Metamer

Pairs of light containing different wavelengths that appear identical; mixtures that look the same but have different wavelengths

29

Test color containing a single wavelength can be matched subjectively to another color containing a ____ of primary wavelengths at different intensities

Mixture

30

Normal observers need how many primaries to match test color

3

31

To explain Metamers, use what curve

Curve of chromatic sensitivity for different cone combos; one side is excitatory and one is inhibitory (positive and negative)

32

Can create curves of chromatic sensitivity for ___ cone combos

Different; single wavelength gives pure hue

33

How many colors result from a single wavelength

3, yellow green and blue

34

Green/red and blue/yellow chromatic sensitivity curve create

3 primaries and range of colors

35

Opponent color theory (psychophysics example)

The theory that perception of color is based on the output of three mechanisms, each of them based on an opponent between two colors; red-green, blue-yellow, black-white

36

LGN has cells that are cone opponent cells

Neurons whose output is based on a difference between sets of cones; center surround (red center, green surround, etc); overall color presence

37

Cone opponent cells subtract ____ of cone input from another

One type

38

In the primary visual cortex, double opponent color cells are found for the first time

More complicated, combine the properties of two color opponent cells from LGN; spots of color

39

Single opponent cells (cone opponent cells)

Red vs green

40

Double opponent cells

R-/G+ in surround, R+/G- in center; more red in center and green in the background gives greater response

41

Color constancy

The tendency of a surface to appear the same color under a fairly wide range of illuminants; see the same color even in a wide range of light sources

42

To achieve color constancy, we must discount the ____ and determine what the true color is regardless of how it appears

Illuminant

43

Illuminant

Light that illuminates a surface

44

Physical constraints make constancy possible

Intelligent guesses about Illuminant, assumptions about light sources, assumptions about surfaces

45

Guesses about Illuminant

Day outside-blue
Inside-yellow
Take into account response across entire retina (horizontal/amacrine)

46

Assumptions about light sources

From above, consistent over space

47

Assumptions about surfaces

Maintain constant surface reflect ants, consistent with prior experience

48

Spectral power distribution

Physical energy in a light as a function of wavelength

49

Color blindness

8% of men and .5% of females

50

Deuteranope

Color blindness from loss of M cones (r/g)

51

Protanope

Color blindness from loss of L cones; r/g

52

Tritanope

Color blindness from loss of S cones; b/y

53

Cone monochromat

Have just one cone type; completely color blind; can't tell color difference, just a difference in light and dark levels