Chapter 5; Color Flashcards
S-cone
cone sensitive to short wavelength; blue cone.
M-cone
cone sensitive to middle wavelength; green cone.
L-cone
cone sensitive to long wavelength, red cone.
Photopic
light intensity that are bright enough to stimulate the cone receptors and bright enough to saturate the rod receptor; maximum responses.
Scotopic
light intensities that are bright enough to stimulate rod receptors but too dim to stimulate cone receptors.
Problem of Univariance
the face 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 color discriminations based on wavelength.
Trichromatic theory of color vision (trichromacy)
the theory that the color of any light is defined in our visual system by the relationships of 3 numbers – the output of 3 receptor types now known to be the 3 cones. AKA Young Helmholtz theory.
metamers
different mixtures of wavelengths that look identical. More generally, any pair of stimuli that are perceived as identical in spite of physical differences.
Additive color mixtures
a mixture of light. If light from A and B are both reflected from a surface to the eye, in the perception of color that effect those two lights add together.
subtractive color mixture
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 from B. Only the remainder contributes to the perception of the color.
Lateral geniculate nucleus (LGN)
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.
cone-opponent cell
a cell type found int he retina, LGN and visual cortex - that in effect, subtract one type of cone input form another
achromatopsia
inability to perceive color that is caused by damage to the central nervous system
adapting stimulus
a stimulus whose removal produces a change in visual perception and sensation
neutral point
the point at which an opponent color mechanism is generating no signal. if red-green and blue-yellow mechanisms are at their neutral point, a stimulus will appear achromatic. (black and white process has no neutral point)
