Task 3 - True Colors

Question 1

Reflectance curve

Answer 1

plots of the percentage of light reflected versus wavelength

Question 2

Chromatic colors, or hues

Answer 2

this property of reflecting some wavelengths more than others, which is a characteristic of chromatic colors

Question 3

Achromatic colors

Answer 3

When light reflection is similar across the full spectrum—that is, contains no hue—as in white, black, and all the grays between these two extremes

Question 4

Selective transmission

Answer 4

things that are transparent, such as liquids, plastics, and glass, chromatic color is created - selective transmission - only some wavelengths pass through the object or substance

Question 5

Additive color mixture

Answer 5

mixing lights

Question 6

Subtractive color mixture

Answer 6

mixing paint

Question 7

Trichromatic theory of color vision

Answer 7

color vision depends on the activity of three different receptor mechanisms

Question 8

Color-matching experiments

Answer 8

observers adjusted the amounts of three different wavelengths of light mixed together in a “comparison field” until the color of this mixture matched the color of a single wavelength in a “test field.”

Question 9

Young-Helmholtz theory of color vision

Answer 9

central idea of the theory is that color vision depends on three receptor mechanisms, each with different spectral sensitivities –According to this theory, light of a particular wavelength stimulates the three receptor mechanisms to different degrees, and the pattern of activity in the three mechanisms results in the perception of a color. Each wavelength is therefore represented in the nervous system by its own pattern of activity in the three receptor mechanisms

Question 10

Metamerism

Answer 10

This situation, in which two physically different stimuli are perceptually identical

Question 11

Metamers

Answer 11

the two identical fields in a color-matching experiment

Question 12

Dichromats

Answer 12

people with just two types of cone pigment

Question 13

Trichromats

Answer 13

they see fewer colors than people with three visual pigments

Question 14

Color deficiency

Answer 14

most problems with color vision involve only a partial loss of color perception – are associated with problems with the receptors in the retina

Question 15

Daltonism

Answer 15

another term for protanopia – another form of color blindness

Question 16

Ishihara plates

Answer 16

color vision test

Question 17

Monochromat

Answer 17

can match any wavelength in the spectrum by adjusting the intensity of any other wavelength. Thus, a monochromat needs only one wavelength to match any color in the spectrum and sees only in shades of gray

Question 18

Unilateral

Answer 18

a person with trichromat vision in one eye and dichromatic vision in the other

Question 19

three major forms of dichromatism:

Answer 19

1. protanopia
2. deutoranopia
3. tritanopia

Question 20

Opponent-process theory of color vision

Answer 20

this theory states that color vision is caused by opposing responses generated by blue and yellow and by red and green – responsible for afterimages

Question 21

Simultaneous color contrast

Answer 21

an effect that occurs when surrounding an area with a color changes the appearance of the surrounded area

Question 22

Opponent neurons

Answer 22

in the retina and lateral geniculate nucleus that responded with an excitatory response to light from one part of the spectrum and with an inhibitory response to light from another part

Question 23

Cerebral achromatopsia

Answer 23

color blindness due to damage to the cortex

Question 24

Color constancy

Answer 24

we perceive the colors of objects as being relatively constant even under changing illumination

Question 25

Chromatic adaptation

Answer 25

prolonged exposure to chromatic color. Adaptation to the red light selectively bleaches your long-wavelength cone pigment, which decreases your sensitivity to red light

Question 26

Partial color constancy

Answer 26

the perception of the object is shifted after adaptation, but not as much as when there was no adaptation – This means that the eye can adjust its sensitivity to different wavelengths to keep color perception approximately constant as illumination changes

Question 27

Memory color

Answer 27

the effect of our knowledge about the usual colors of objects in the environment

Question 28

Lightness constancy

Answer 28

The fact that we see whites, grays, and blacks as staying about the same shade under different illuminations is called

Question 29

The visual system’s problem is that the amount of light reaching the eye from an object depends on two things

Answer 29

(1) the illumination: the total amount of light that is striking the object’s surface—and
(2) the object’s reflectance - the proportion of this light that the object reflects into our eyes

Question 30

Ratio principle

Answer 30

as long as this ratio remains the same, the perceived lightness will remain the same

Question 31

Reflectance edge

Answer 31

an edge where the reflectance of two surfaces changes

Question 32

Illumination edge

Answer 32

an edge where the lighting changes

Question 33

Penumbra

Answer 33

the fuzzy border at the edge of the shadow – the penumbra provides information to the visual system that the dark area next to the cup is a shadow, so the edge between the shadow and the paper is an illumination edge. However, masking off the penumbra eliminates that information, so the area covered by the shadow is seen as a change in reflectance

Question 34

Principle of univariance

Answer 34

one and the same visual receptor cell can be excited by different combinations of wavelength and intensity, so that the brain cannot know the color of a certain point of the retinal image