color part 2

Question 1

opponent proces theory

Answer 1

color perception is based on 4 primary colors
based on 3 opponent mechanisms
3D construct

Question 2

what are the 3 opponents and why

Answer 2

red-green, blue-yellow, white-black

- impossible to have a color in between

Question 3

complementary afterimages

Answer 3

when staring at one color too long eye wonders if calibration is off so shifts balance of scale and over-corrects so you see the opposite color

Question 4

hue cancellation experiments

Answer 4

ex. how much yellow to cancel the blue

Question 5

opponent cells

Answer 5

• cells that are inhibitory to one color and excitatory to another
• opposite responses
• receptors wired together

Question 6

how do the trichromatic and opponent process theories work together

Answer 6

at the level of cones: trichromatic theory responds (color matching)
the output of cones gets integrated: opponent process theory (hue cancellation)

Question 7

what do these two theories not explain

Answer 7

• why our eyes can be tricked when placing a solid bar in front of a gradient
• determining if colors are the same or different
• scintillating grid illusion

Question 8

what does the light reflecitng off an object depend on (2)

Answer 8

1. reflectance- how the object reflects light
2. illumination- how light falls on the object
   light arriving at eye is a combination of light available, and how it reflects

Question 9

lightness constancy

Answer 9

we tend to perceive whites, grays and blacks the same under varying illumination
- ratio principle: under even illumination, the ratio of reflected light guides perception of lightness

Question 10

illumination edges

Answer 10

same surface, different illumination

Question 11

reflectance edges

Answer 11

different surface, same illumination

Question 12

color constancy

Answer 12

we tend to perceive objects with the same reflectance as having the same color under varying illumination

Question 13

chromatic adaptation

Answer 13

• if light arriving at eye is red, and light shining on paper is red, brain adapts and recognizes that the paper is still green
• if light arriving at eye is white, and red on paper, brain will perceive the paper as red (trick the eye)

Question 14

chromatic adaptation (environment example)

Answer 14

lush environment- tones down greeness so other aspects stand out and you can distinguish between greens
arid (little green)- cranks up green to help distinguish

Question 15

factors that influence color constancy

Answer 15

chromatic adaptation- receptors for a color adapt over continuous stimulation
context- infer wavelength of illumination
memory- knowledge of things in the world effects how we perceive them