Color Vision Flashcards
3 steps to color perception and definitions
detection
- must be able to sense light in the first place
discrimination
- must be bale to differentiate between different wavelengths or mixtures of them (ex. bar of light vs. edge)
appearance
- we assign perceived colors to different objects in the world and assume such colors are stable, even if the overall lighting changes
3 types of opsins for cones
short: blue range
medium: green range
long: red range
opsins
what wavelengths the eye responds to
- dictate their color sensitivity
what two cones are close to each other in wavelength?
medium and long/green and red!
opsin type for rods
rhodopsin; not full color
scotopic vision is __________ (what does this mean?)
univariate
- in scotopic conditions, rods work alone meaning all color processing is translated into 1 response
- lots of variables into 1
why is color vision so bad at night?
because scotopic vision is univariate but also trying to process infinite color (which cannot be fully processed by rods)
rods all respond the same to _____, with a ______ response
color; graded (meaning colors on either side produce a similar response)
trichromatic theory of color vision
any light perception in human vision is dictated by combining 3 variables (S,M,L) - aka the Young-Helmholtz Theory
metamers
different mixtures of light that are perceived as identical, despite having different generators
items look the same in given light but are actually different shades
while not univariate, cones still end up coming to the same consensus for different color combinations, meaning
visual system comes to a decision/compromise at what it is seeing
when red and green/long and medium wavelengths are fired in the cones, this creates the perception of what color?
yellow!
what study showed that light is additive?
maxwell’s color matching experiment
light is _____ while paint is ______
additive; subtractive
3 factors of color and definitions
hue - the color (RGB)
saturation - the strength of the hue (aka the distance from white)
brightness - the distance from black
four unique hues
a color that has no hint of another primary color in it
4 main colors: red, yellow, green, blue
yellow and blue don’t mix while red and green don’t mix
how to test unique hues?
cancelling colors
adding blue to yellow until it contains neither blue nor yellow, only green
main takeaway of color canceling with four unique hues
result in 2 spectrums:
yellow-blue
green-red
cone opponent cells
cells that track the difference in output between sets of cones
example of concentric double-opponent cone cell
red inside with green border then green outside with red border
example of single-opponent cone cell
red inside with green outside
achromatopsia
brain derived full color vision loss
3 opponent mechanisms for cones
red-green
yellow-blue
white-black
negative afterimages for opponent processing
can see the image still but in opposite colors
light –> dark
red –> green
blue –> yellow
color contrast
perceptual effect where the same color appears different when paired with a similar or an opponent color
ex) the center squares appear differently depending on their surround
color assimilation
perceptual effect where colors “bleed” into each other, each taking on some of the chromatic quality of the other
ex) pointillism!
color constancy
generally, despite lots of changes in overall lighting, we perceive a given object as the same color
what do we discount with color constancy
the illuminant
- the light itself hitting an object’s surface
what do we assume with color constancy
broadband light
- entire visible spectrum
assume the surfaces are broadband too and reflect most wavelengths
example of color constancy
the dress from 2015!
the illuminant
- blue light source = white stripe
- yellow light source = blue stripe!
also depends on mental reference
cultural relativism
idea that basic perceptual experiences (e.g., color perception) may be determined in part by the cultural environment
color-anomalous
not fully color blind; perception of wavelengths altered
color-anomalous types
deuteranope
- due to absence of M-cones “green”
protanope
- due to absence of L-cones “red”
^^both similar^^
tritanope
- due to absence of S-cones “blue”
cone monochromat
- only 1 cone type; truly color-blind
rod monochromat
- no cones of any type; truly color-blind and very visually impaired in bright light
color is tied to lots of other _________
processing/senses
synesthesia
when one stimulus evokes the experience of another stimulus that is not present
ex) hear music but see colors because of it!
This theory of color vision suggests all light perception can be broken down into combinations of 3 colors:
a) Opponent Process Theory
b) Trichromatic Color Theory
c) Color Contrast Theory
d) Color Constancy Theory
B
A “single opponent” cell in LGN is found to have a S+
(Blue) center receptive field. What would we most likely label its surround?
a) L- (Red)
b) M- (Green)
c) S- (Blue)
d) L-/M- (Red+Green)
D; red+green make yellow = blue-yellow opponent processing
Juan conducts an experiment wherein he has participants stare at colored dots, and then after awhile has them look at a gray set of dots, resulting in them seeing the opposite colors. What technique is Juan using?
a) Selective adaptation
b) The method of limits
c) Color mixing
d) Illuminant discounting
A
