Color Vision

Question 1

Hue

Answer 1

The color: Hue is related to wavelength (relation is not simple)

Question 2

Saturation

Answer 2

The distribution of light, The more pure, the more saturation, Many different wavelengths is referred to as being broadband

Question 3

Brightness

Answer 3

The intensity of light, Light to dark

Question 4

Functions of color vision

Answer 4

having color vision makes it easier to discriminate good food from bad food, obj detection, obj recognition and identification

Question 5

Color mixing: Additive

Answer 5

Adding lights. A mixture of lights. If light A and light B are both reflected from a surface to the eye, in the perception of color the effects of those two lights add together.

Question 6

color mixing: Subtractive

Answer 6

Adding pigments. A mixture of pigments. If pigments A and B mix, some of the light shining on the surface will be subtracted by A. and some by B. Only the remainder will contribute to the perception of color. Each pigment reflects a certain band of wavelengths

Question 7

Color contrast: simultaneous

Answer 7

Your perception of an object may be different due to different backgrounds OR a color in one part in the visual field affects your perception of another color

Question 8

Color contrast: successive

Answer 8

Referred to as Afterimages, think of when you stare at an image for a long time and it gives an “after effect” when you see another image.

Question 9

Negative afterimages

Answer 9

an afterimage whos polarity is the opposite of the original stimulus. Light stimuli produce dark negative afterimages. Colors are complementary; for example, red produces green, and yellow produces blue.

Question 10

Color blindness- color deficiency observation

Answer 10

People who are color-blind to red are also color-blind to green.
  People who are color-blind to blue are also color-blind to yellow.

Question 11

color blindness- Herring’s Observation

Answer 11

Types of Color deficiencies – Red-green color blindness – Blue-yellow color blindness; Color-normal people can’t see red-green together, nor blue-yellow together

Question 12

Wavelength sensitivity of cones

Answer 12

S-cones = SHORT wavelengths (blue cones) M-cones = MIDDLE wavelength (green cones)
L-cones = LONG wavelengths (red cones)

Question 13

The problem of univariance:

Answer 13

different wavelength-intensity combinations can elicit exactly the same response from a single type of photoreceptor. Need multiple types to discriminate. (Univariance = there’s only 1 quantity (one dimension of input and one of output) that can vary).

Question 14

Theories for color perception

Answer 14

trichromatic & opponent

Question 15

Trichromatic theory

Answer 15

With three cone types we can tell the difference between lights of different wavelengths.

Question 16

Evidence for the theory

Answer 16

3 Receptors →3 primary color sensations: Blue, Green, Red. (Yellow is claimed to be combination of green & red)

Question 17

color matching experiment

Answer 17

By adjusting proportions of 3 wavelengths it’s possible to match the color of comparison to a single wavelength testfield, but need at least three wavelengths to match all wavelengths in spectrum

Question 18

Opponent color theory

Answer 18

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

Question 19

Evidence for the theory

Answer 19

Better at explaining simple and complex colors, contrast, exclusivity (no bluish yellow), and the color yellow itself; Physiological evidence, Opponent neurons: B+Y-, Y+B-, G+R-, R+G-

Question 20

color phenomena and our intuition

Answer 20

1. Color Mixing 2. Contrast
2. Intuitions
3. Color Blindness
4. Color Cancellation

Question 21

hue cancellation experiment

Answer 21

Famous experiments: Hurvich & Jameson (1957) Cancellation experiments estimated the strength of each mechanism along the wavelength dimension.

Question 22

Unique hues

Answer 22

any of four colors that can be described w/only a single color term: red, yellow, green, blue. (other colors (e.g., purple or orange) can also be described as compounds (reddish blue, reddish yellow).

Question 23

Putting the two theories together

Answer 23

As an account of color experience, Young Helmholtz theory is incorrect; • Color vision is trichromatic, however, in an important sense: based on 3 mechanisms at the retina

Question 24

A two-stage processing

Answer 24

The FIRST stage of color processing is captured well by the trichromatic theory (color matching), and the SECOND stage of color processing captured well with the opponent-process theory (afterimages, simultaneous contrast).

Question 25

Color constancy

Answer 25

Physical constraints help with achieving constancy: – Intelligent guesses about the illuminant – Assumptions about light sources – Assumptions about surfaces • These mechanisms are also involved in:
– Chromatic adaptation
– Memory color

Question 26

Color adaptation

Answer 26

The eye adjusts its sensitivity to different wavelengths and this helps achieve partial color constancy.

Question 27

Color memory

Answer 27

Characteristic color of familiar objects affects their color perception. • People judge the familiar objects to have a richer more saturated color than unfamiliar objects with the same wavelengths