Perception Of Color Flashcards
(28 cards)
Cone sensitive to middle wavelengths; known as “green cone”
M-cone (middle)
A cone that is preferentially sensitive to long wavelengths; known as “red cone”
L-cone (long)
A cone that is preferentially sensitive to short wavelengths; colloquially (but not accurately known as a “blue cone”
S-cone (short)
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.
additive color mixture
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 contributes to the perception of color.
subtractive color mixture
A structure in the thalamus, part of the midbrain, that receives input from the retinal ganglion cells and has input and output connections to the visual cortex.
lateral geniculate nucleus (LGN)
A cell type—found in the retina, lateral geniculate nucleus, and visual cortex—that, in effect, subtracts one type of cone input from another.
cone-opponent cell
A photopigment, found in a class of photoreceptive retinal ganglion cells, that is sensitive to ambient light.
melanopsin
The theory that perception of color is based on the output of three mechanisms, each of them resulting from an opponency between two colors: red-green, blue-yellow, and black-white.
opponent color theory
A cell type, found in the visual cortex, in which one region is excited by one cone type, combination of cones, or color and inhibited by the opponent cones or color (e.g., R+/G–).
double-opponent cell
Another way to refer to cone-opponent cells, in order to differentiate them from double-opponent cells.
single-opponent cell
An individual with only one cone type. These individuals are truly color-blind.
cone monochromat
An individual with no cones of any type. In addition to being truly color-blind, these individuals are badly visually impaired in bright light.
rod monochromat
A failure to recognize objects in spite of the ability to see them. Typically due to brain damage.
agnosia
An inability to name objects in spite of the ability to see and recognize them (as shown by usage).
Anomia is typically due to brain damage
A color perception effect in which the color of one region induces the opponent color in a neighboring region.
color contrast
An afterimage whose polarity is the opposite of the original stimulus
negative afterimage
The three types of cones in the human visual system are
S-cones, M-cones, and L-cones. They are all collectively responsible for discriminating between different colors. The S-cones are preferentially sensitive to short wavelengths (e.g., “blue”), the M-cones are preferentially sensitive to middle wavelengths (e.g., “green”), and the L-cones are preferentially sensitive to long wavelengths (e.g., “red”).
The three steps to color vision are
1) Detection during which wavelengths of light are first registered by the visual system; 2) Discrimination during which different wavelengths of light are distinguished from each other; and 3) Appearance during which viewing conditions are taken into account while producing the final percept of a scene.
What is the principle of univariance
The principle of univariance is the fact that an infinite set of different wavelength–intensity combinations can elicit exactly the same response from a single type of photoreceptor. One photoreceptor type cannot make accurate color discriminations by itself.
What does the trichromatic theory of color vision tell us about color perception?
The trichromatic theory of color vision tells us that the color of any light is defined in our visual system by the relationships between the outputs of the three cone types.
What is an additive color mixture?
An additive color mixture is when two sources of illumination combine to make a new color, as when mixing lights. If light A and light B are both reflected from a surface to the eye, the colors of those two lights add together.
What is a subtractive color mixture?
A subtractive color mixture is when one source of illumination is subtracted from another, as when two color filters are placed in front of a light source or when pigments are mixed. 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 remaining light that was not absorbed by either A or B contributes to the perception of color.
What happens if you shine “blue” and “yellow” lights on the same patch of paper?
If you shine “blue” and “yellow” lights on the same patch of paper, the wavelengths will add, producing an additive color mixture. Since “yellow” is equivalent to a mix of long and medium wavelengths, and “blue” consists of short wavelengths, the two lights will produce a mixture of short, medium, and long wavelengths. The resulting mixture will therefore look “white.”
