Color and Color Vision

Spectral Reflectance

The percentage of light at each wavelength that an object's surface reflects. This is what determines an object's color.

Hue

attribute of color related to wavelength.

Saturation

purity/vividness of a color.

Subtractive Color Mixture

mixing substances, each absorbs certain wavelengths.

Additive Color Mixture

mixing light wavelengths, adding intensities.

Helmholtz Trichromatic Theory

vision based on three cone types (red, green, blue).

Metamers

Two lights that have different wavelength compositions but are perceived as the same color.

Spectral Sensitivity Function

cones differ in the likelihood that they will absorb photons of light of a particular wavelength, but once a photon is absorbed, its effect is the same for all wavelengths

Principle of Univariance

The principle that a single photoreceptor's firing rate is determined only by the total number of photons it absorbs, not by the wavelength of those photons. Meaning one type of photoreceptor cannot distinguish between different wavelengths.

Opponent Process Theory

The idea that we perceive color in terms of opposing pairs: red vs. green, blue vs. yellow, and black vs. white

Photopigment Bleaching

the process where light exposure causes photopigments in the eye (especially in cone cells) to break down, temporarily reducing their sensitivity to light and color

Chromatic Adaptation

the eye's ability to adjust to changes in lighting so that the colors of objects appear consistent, even when the light source changes

Color Contrast

The effect of an adjacent color on the perception of a color. For example, a gray square looks bluish on a yellow background.

Color Assimilation

The opposite of color contrast, where a color appears to take on the hue of an adjacent color.

Color Constancy

surface appears same color under different lighting.

Lightness

perceived reflectance of a surface.

Lightness Constancy

The ability to perceive the lightness of a surface as constant under different lighting conditions

Isaac Newton

discovered white light contains all colors; prism splits it into spectral components.

Spectral Components

The different wavelengths of light that make up a light source

Purkinje Shift

as lighting conditions change there's a change in the wavelengths we are more sensitive to

Afterimage

when you're exposed to one color for a prolonged amount of time, and are then exposed to white light, then you will see the after color of the original image

Pure Color

a single wavelength corresponds to a single color