COLOR VISION Shirmeen Ijaz COLOR The most technically

COLOR VISION Shirmeen Ijaz

COLOR � The most technically accurate definition of color is: "Color is the visual effect that is caused by the spectral composition of the light emitted, transmitted, or reflected by objects. “

� � � The human eye senses this spectrum using a combination of rod and cone cells for vision. Three types of cone cells exist in your eye, with each being more sensitive to either 1)S-cone: Short (S) wavelength light. 2) M-cone: Medium (M) wavelength light. 3) L-cone: Long (L) wavelength light.

Color-Processing in Vision BLUE CONES 2% OF THE CONE POPULATION • Found mostly outside the fovea GREEN CONES 32% OF THE CONE POPULATION • Packed into the fovea RED CONES 64% OF THE CONE POPULATION • Packed into the fovea

� � � Color can only exist when three components are present: 1) a viewer, 2) an object, 3) light. Although pure white light is perceived as colorless, it actually contains all colors in the visible spectrum. When white light hits an object, it selectively blocks some colors and reflects others; only the reflected colors contribute to the viewer's perception of color.

� 1. All the "invisible" colors of sunlight shine on the apple. 2. The surface of a red apple absorbs all the colored light rays, except for those corresponding to red, and reflects this color to the human eye. 3. The eye receives the reflected red light and sends a message to the brain.

COLOR WHEEL

THEORIES OF COLOR VISION: - Trichromatic theory � 2) Opponent process theory � 1)

Trichromatic theory � � � Given by Thomas Young. Primary colors Red Green Blue Every color (hue) can be created by blending light of the three primary colors in differing proportions

Wavelength Input Cone “Blue” “Green” “Red” Signal to Brain Blue

Theories of Color Vision: Trichromatic Theory Wavelength Input Cone Signal to Brain “Blue” “Green” “Red” Green

Theories of Color Vision: Trichromatic Theory Wavelength Input Cone Signal to Brain “Blue” “Green” “Red” Red

Theories of Color Vision: Trichromatic Theory Wavelength Input Cone Signal to Brain “Blue” Equal Parts Red and Green = “Green” Yellow “Red”

Theories of Color Vision: Trichromatic Theory Wavelength Input Cone Signal to Brain “Blue” Equal Parts Red and Green = “Green” Yellow “Red”

Theories of Color Vision: Trichromatic Theory Wavelength Input Cone Signal to Brain “Blue” Equal Parts Red and Green = “Green” Yellow “Red”

Opponent-Process theory Given by Ewald Hering he noted that there are certain pairs of colors one never sees together at the same place and at the same time. Red/Green � Yellow/Blue � Black/White � If one color is stimulated, the other is inhibited.

According to Hering, there are 3 types of color receptors, but they are not sensitive only to red, green and blue. � He also claimed, a color could be a reddish yellow or a bluish green, but not a reddish green or a bluish yellow. �

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