Topic 9: Color Perception Flashcards
Cerebral Achromatopsia
a loss of color vision caused by damage to the cortex
Color Deficiency
condition (sometimes incorrectly called color blindness) in which people see fewer colors than people with normal color vision and need to mix fewer wavelengths to match any other wavelength in the spectrum
Chromatic Colors
color with hue, such as blue, yellow, red, or green
Selective Reflection
when an object reflects some wavelengths of the spectrum more than others
Reflectance Curves
a plot showing the percentage of light reflected from an object versus wavelength
Selective Transmission
when some wavelengths pass through visually transparent objects or substances and others do not
selective transmission is associated with the perception of chromatic color
Transmission Curves
plots of the percentage of light transmitted through a liquid or object at each wavelength
Subtractive Color Mixture
both paints still absorb the same wavelengths they absorbed when alone, so the only wavelengths reflected are those that are reflected by both paints in common
Additive Color Mixture
all of the light that is reflected from the surface by each light when alone is also reflected when the lights are superimposed
Spectral Colors
colors that appear in the visible spectrum
Non-spectral Colors
colors that do not appear in the spectrum because they are mixtures of other colors
an example is magenta, which is a mixture of red and blue
Hues
the experience of a chromatic color, such as red, green, or yellow, or blue, or combinations of these colors
Saturation
the relative amount of whiteness in a chromatic color
the less whiteness a color contains, the more saturated it is
Desaturated
low saturation in chromatic colors as would occur when white is added to a color
for example, pink is not as saturated as red
Value
the light-or-dark dimension of color
Lightness
the perception of shades ranging from white to gray to black
Color Solid
a solid in which colors are arranged in an orderly way based on their hue, saturation, and value
Munsell Color System
depiction of hue, saturation, and value developed by Albert Munsell in the early 1900s in which different hues are arranged around the circumstance of a cylinder with perceptually similar hues placed next to each other
Trichromacy of Color Vision
the idea that our perception of color is determined by the ratio of activity in three receptor mechanisms with different spectral sensitivities
also known as the Young-Helmholtz theory
Color Matching
a procedure in which observers are asked to match the color in one field by mixing to or more lights in another field
Microspectrophotometry
a technique in which a narrow beam of light is directed into a single visual receptor
this technique makes it possible to determine the pigment absorption spectra of single receptors
Adaptive Optical Imaging
a technique that makes it possible to look into a person’s eye and take pictures of the receptor array in the retina
Aberrations
imperfections on the eye’s cornea and lens that distort light on its way to the retina
Cone Mosaic
arrangement of short-, medium-, and long-wavelength cones in a particular part of the retina
Metamerism
the situation in which two physically different stimuli are perceptually identical
in vision, this refers to two lights with different wavelength distributions that are perceived as having the same color
Metamers
two lights that have different wavelength distributions but are perceptually identical
Monochromatism
rare form of color blindness in which the absence of cone receptors results in perception only of shades of lightness (white, gray and black), with no chromatic color present
Monochromats
a person who is completely color-blind and therefore sees everything as black, white, or shades of gray
a monochromat can match any wavelength in the spectrum by adjusting the intensity of any other wavelength
monochromats generally have only one type of functioning receptors, usually rods
Color Blind
a condition in which a person perceives no chromatic color
this can be caused by absent or malfunctioning cone receptors or by cortical damage
Dichromats
a person who has a form of color deficiency
dichromats can match any wavelength in the spectrum by mixing two other wavelength
Trichromats
a person with normal color vision
trichromats can match any wavelength in the spectrum by mixing three other wavelengths in various proportions
Ishihara Plates
a display of colored dots used to test for the presence of color deficiency
the dots are colored so that people with normal (trichromatic) color vision can perceive numbers on the plate, but people with color deficiency cannot perceive these numbers or perceive different numbers than someone with trichromatic vision
Unilateral Dicrhomat
a person who has dichromatic vision in one eye and trichromatic vision in the other eye
people with this condition (which is extremely rare) have been tested to determine what colors dichromats perceive by asking them to compare the perceptions they experience with their dichromatic eye and their trichromatic eye
Dichromatism
a form of color deficiency in which a person has just two types of cone pigment and so can see chromatic colors but confuse some colors that trichromats can distinguish
Protanopia
a form of dichromatism in which a protanope is missing the long-wavelength pigment, and perceives short-wavelength light as blue and long-wavelength light as yellow
Neutral Point
the wavelength at which a dichromat perceives gray
Deuteranopia
a form of dichromatism in which a person is missing the medium-wavelength pigment
a deuteranope perceives turquoise at short wavelengths, sees yellow at long wavelengths, and has a neutral point at about 498 nm
Tritanopia
a form of dichromatism in which a person is missing the short-wavelength pigment
a tritanope sees blue at short wavelengths, red at long wavelengths
Anomalous Trichromatism
a type of color deficiency in which a person needs to mix a minimum of three wavelengths to match any other wavelength in the spectrum but mixes these wavelengths in different proportions than a trichromat
Opponent-Process Theory of Color Vision
a theory originally proposed by Hering, which claimed that our perception of color determined by the activity of two opponent mechanisms
a blue-yellow mechanism and a red-green mechanism
the responses to the two colors in each mechanism oppose each other, one being an excitatory response and the other an inhibitory response
in addition, this theory also includes a black-white mechanism, which is concerned with the perception of brightness