Color Vision: Sensing a Colorful World

Psychological experience of visionTrichromatic TheoryOpponent-Process Theory

The stimulus for vision is LIGHT

Light travels in the forms of waves. Waves affect three aspects of our

visual world: Hue, brightness, and saturation. All 3 are PSYCHOLOGICAL

DIMENSIONS OF VISUAL EXPERIENCE.

Hue “Experts estimate that we can distinguish perhaps as many as 10 million

colors.“ Wyszecki, Gunter. Color. Chicago: World Book Inc, 2006: 824.

Specified by color names Hue is related to the wavelength of

light.

Brightness

Is related to the amount, or intensity, of the light an object emits or reflects.

Height of the wavelength. The more light an object reflects,

the brighter it appears.

Saturation (colorfulness)

Related to the complexity of the light, how wide or narrow the wave is.

Trichromatic Theory proposed by T. Young and H. vov Helmholtz

Our eyes detect 3 primary colors-red, blue, and greenThree receptors (cones) with differing

sensitivities to different light wavelengths.

+ People can see all the colors of the rainbow because the eye does its own “color mixing” by varying the ratio of neural activity among these three types of receptors

Wavelengths of light

Blue-violet cones are most sensitive to short wavelengths of light

Wavelengths of light

Green cones are most sensitive to middle wavelengths

Wavelengths of light

Red cones are most sensitive to long wavelengths.

Color Blindness

Encompasses a variety of deficiencies in the ability to distinguish among colors.

Occurs much more frequently in males than in females

Dichromats (10% of men and 1% of women) they make do with only two types of color receptors.

Receptors may be insensitive to red, green, or blue (latter is rare).

Assumes that the visual system treats pairs of colors as opposing or antagonistic.

Yellow vs. Blue Red vs. Green Black vs. White

Black-white receptors detect brightness or shades of gray

Opponent Processing Theory (Ewald Hering)

O-P theory helps to explain…

Afterimage effect: Stare at a blue circle for a while, you

see a yellow circle briefly on a white sheet of paper.

O-P Theory

explain why dichromats typically find it hard to distinguish either green from red or yellow from blue.

Monochromates

Rare disorder in which a person can not detect any colors. Respond only to shades of light and dark.