Chapter 5-the Perception Of Color

Question 1

Color descriptions use how many attributes and what are they

Answer 1

3; hue, brightness, saturation

Question 2

Hue

Answer 2

“Color”; chromatic aspect of light

Question 3

Saturation

Answer 3

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

Question 4

Brightness

Answer 4

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

Question 5

How many axes

Answer 5

2; red vs green and blue vs yellow

Question 6

RBG

Answer 6

Different color space to define wavelength present

Question 7

Subtractive color mixing

Answer 7

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

Question 8

When you subtract all wavelengths you see what color

Answer 8

You get black

Question 9

White light has what wavelength color

Answer 9

All colors

Question 10

Mixing blue and yellow make green-how

Answer 10

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

Question 11

Color printer cartridge has what colors

Answer 11

MCY (magenta, cyan, yellow); subtractive

Question 12

Computer screen has what wavelengths

Answer 12

Red, green, blue; additive

Question 13

Additive color mixing

Answer 13

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

Question 14

When all the wavelengths are added together, what color

Or when just red, blue and green added

Answer 14

White

Question 15

S cones

Answer 15

Detect short wavelengths (420-ish), blue

Question 16

M cones

Answer 16

Detect medium wavelengths (535-ish) green

Question 17

L cones detect

Answer 17

Long wavelengths (565-ish) red

Question 18

Cone photoreceptors aren’t called by the color because

Answer 18

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

Question 19

Problem of univariance

Answer 19

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

Question 20

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

Answer 20

Cannot

Question 21

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

Answer 21

Respond

Question 22

Photopic

Answer 22

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

Question 23

Scotopic

Answer 23

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

Question 24

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

Answer 24

Relative

Question 25

Under Photopic conditions, what cones are active

Answer 25

S, m and l

Question 26

Trichromacy (young helmholtz theory)

Answer 26

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

Question 27

Additive mixture uses what material

Answer 27

Metamers

Question 28

Metamer

Answer 28

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

Question 29

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

Answer 29

Mixture

Question 30

Normal observers need how many primaries to match test color

Answer 30

3

Question 31

To explain Metamers, use what curve

Answer 31

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

Question 32

Can create curves of chromatic sensitivity for ___ cone combos

Answer 32

Different; single wavelength gives pure hue

Question 33

How many colors result from a single wavelength

Answer 33

3, yellow green and blue

Question 34

Green/red and blue/yellow chromatic sensitivity curve create

Answer 34

3 primaries and range of colors

Question 35

Opponent color theory (psychophysics example)

Answer 35

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

Question 36

LGN has cells that are cone opponent cells

Answer 36

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

Question 37

Cone opponent cells subtract ____ of cone input from another

Answer 37

One type

Question 38

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

Answer 38

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

Question 39

Single opponent cells (cone opponent cells)

Answer 39

Red vs green

Question 40

Double opponent cells

Answer 40

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

Question 41

Color constancy

Answer 41

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

Question 42

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

Answer 42

Illuminant

Question 43

Illuminant

Answer 43

Light that illuminates a surface

Question 44

Physical constraints make constancy possible

Answer 44

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

Question 45

Guesses about Illuminant

Answer 45

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

Question 46

Assumptions about light sources

Answer 46

From above, consistent over space

Question 47

Assumptions about surfaces

Answer 47

Maintain constant surface reflect ants, consistent with prior experience

Question 48

Spectral power distribution

Answer 48

Physical energy in a light as a function of wavelength

Question 49

Color blindness

Answer 49

8% of men and .5% of females

Question 50

Deuteranope

Answer 50

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

Question 51

Protanope

Answer 51

Color blindness from loss of L cones; r/g

Question 52

Tritanope

Answer 52

Color blindness from loss of S cones; b/y

Question 53

Cone monochromat

Answer 53

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