Color Vision #2 Flashcards
All real, visible colors an be described a mixture of the
3 imaginary primaries
Trichromatic theory was created by who
Young and Helmholtz
What did the trichromatic theory suggest? What psychophysical support did it have then? What neurophysical support does it have now?
Suggested that trichromacy is a property of the eye. Color vision based on 3 mechanisms/sensitive particles in the retina.
Psychophysical support:
- Normal human ability to match any color with mixture of three primaries.
- Three congenital affects of human color vision based on 3 cone receptors.
Neurophysical support:
1. Three cone pigments
The trichromatic theory is unable to account for what
- Some color mixture results. Why we never describe a color as red/green or blue/yellow. (Accounted for by color opponent theory)
- Chromatic after effect (look at something blue, will see yellow after image due to color opponency)
- Simultaneous color contrast
- Color constancy (accounted for by the retinex theory)
Who came up with the opponent color theory
Hering
What did the opponent color theory propose
He postulated that there were neural visual response channels, one of which signaled red OR green, another that signaled blue OR yellow, and another that signaled white OR black.
Opponent color theory explained which two mysteries that the trichromacy theory didn’t explain?
Explained color mixtures (Why we never call colors blue/yellow or red/green)
Explained chromatic after effect. Adapt to yellow color. When you look at a white background after looking at yellow, the white will stimulate all colors equally, except yellow because it will be fatigued. Therefore, the blue will be seen.
Ganglion cell spectral opponency and the opponent color theory
Red on/green off and green on/red off. Center/surround
Blue on/yellow off is NOT center surround. Blue and yellow receptors make up different regions. Spatially, does not matter. Only wavelength matters. Has much bigger receptive field than red and green.
What type of GC carry the blue/yellow opponancy info? What else are they involved in?
Bistratified. They have 3x greater receptive fields than midges. Also involved in melanopsin-containing GC.
Zone theory was established by who
Jameson and Hurvich
What is the Zone theory?
Combined trichromatic theory and opponent color theory to advocate that vision is trichromatic at the receptor level and that opponent processes occur in the neural elements of the retina and visual pathways.
The zone theory stated that ___ system contributed a lot towards luminance.
Red/green. This is a controversial idea.
Who came up with the Retinex Theory?
Edwin Land.
Retinex theory
Explained color constancy.
Color constancy is the tendency of object to retain the same color appearance despite changes in their illumination and therefore, the wavelength of light they reflect.
The visual system discounts the illuminant in order to perceive color that is consistent with its known context. Context matters more than wavelength.
Context matters more than wavelength is explained by which theory
Retinex
