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46 Cards in this Set
- Front
- Back
Color
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Not a physical property but rather a psychophysical property
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Detection
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Wavelengths of light must be detected in the first place
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Discrimination
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We must be able to tell the difference between one wavelength (or mixture of wavelengths) and another
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Appearance
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We want to assign perceived
colors to lights and surfaces in the world and have those perceived colors be stable over time, regardless of different lighting conditions |
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S-cones
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detect short wavelengths
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M-cones
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detect medium wavelengths
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L-cones
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detect long wavelengths
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Photopic
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Light intensities that are bright enough to
stimulate the cone receptors and bright enough to “saturate” the rod receptors |
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Scotopic
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Light intensities that are bright enough to
stimulate the rod receptors but too dim to stimulate the cone receptors |
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The problem of univariance
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An infinite set of different wavelength–intensity combinations can elicit exactly the same response from a single type of photoreceptor
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Rhodopsin
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All rods contain the same photopigment
molecule |
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Trichromatic theory of color vision (trichromacy)
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The theory that the color of any light
is defined in our visual system by the relationships of three numbers, the outputs of three receptor types now known to be the three cones. Also known as the Young–Helmholtz theory |
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Isaac Newton
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discovered that white light is composed of a spectrum of hues by using a prism And that adding a second prism, recombined the hues into a white light!!
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Metamers
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Mixtures of different wavelength that
look identical.any pair of stimuli that are perceived as identical in spite of physical differences |
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Additive color mixture
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A mixture of lights.
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Subtractive color mixing
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A mixture of pigments! If pigment 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 |
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Cone-opponent cell
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A neuron whose output is
based on a difference between sets of cones. |
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Color space
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A three-dimensional space that describes all colors. There are several possible color spaces
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RGB color space
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Defined by the outputs of short, medium, and long wavelength lights
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HSB color space
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Defined by hue, saturation, and brightness
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Hue
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The chromatic (color) aspect of light
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Saturation
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The chromatic strength of a hue G
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Brightness
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The distance from black in color space
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Opponent color theory
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The theory that perception
of color is based on the output of three mechanisms, each of them based on an opponency between two colors: Red–green blue–yellow black–white |
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Ewald Hering (1834–1918)
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noticed that some color combinations are legal while others are illegal
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hue cancellation
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paradigm (typical example) to
determine the wavelengths of unique hues |
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Unique hue
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Any of four colors that can be
described with only a single color term: Red, yellow, green, blue |
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Cerebral achromatopsia
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An inability to perceive colors; caused by damage to the central nervous system
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Afterimages
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A visual image seen after a stimulus has been removed
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Negative afterimage
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An afterimage whose polarity is the opposite of the original stimulus.
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Colors are complementary
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Red produces green (and vice-versa)
Yellow produces blue (and vice-versa) |
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Deuteranope
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Due to absence of M-cones
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Protanope
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Due to absence of L-cones
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Tritanope
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Due to absence of S-cones
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Color-anomalous
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Two of cones are so similar that they can’t make discriminations based on them
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Cone monochromat
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Only one cone type; truly color-blind
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Rod monochromat
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No cones of any type; truly color-blind, badly visually impaired in bright light
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Cultural relativism
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In sensation and perception, the idea that basic perceptual experiences (e.g., color perception) may be determined in part by the cultural environment
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Roberson et al. (1999)
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work with the Berinmo (a few color words), plus a new color distinction in the GREEN space.
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Color contrast
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A color perception effect in which the color of one region induces the opponent color in a neighboring region
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Color assimilation
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A color perception effect in which two colors bleed into each other, each taking on some of the chromatic quality of the other
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Related color
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A color, such as brown or gray, that is seen only in relation to other colors
A “gray” patch in complete darkness appears white A “brown” patch will look yellow or orange. |
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Color constancy
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The tendency of a surface to appear the same color under a fairly wide range of illuminants
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Illuminant
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The light that illuminates a surface (source of light)
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Assumptions about surfaces
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real surfaces reflect a wide range of wavelengths
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Synesthesia
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Most common: grapheme --> color synthesia
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