Color Perception & Vision Vocabulary

Vocabulary flashcards covering key terms related to the visible spectrum, cone types, color perception mechanisms, spectral reflectance, and common forms of color blindness.

Visible Spectrum

The portion of the electromagnetic spectrum (about 400–700 nm) that the human eye can detect as light.

Nanometer (nm)

A unit of length equal to one billionth of a meter; used to specify light wavelengths (e.g., 500 nm).

S-cones

Short-wavelength photoreceptors in the retina, most sensitive to light around 400–500 nm (blue/violet).

M-cones

Medium-wavelength photoreceptors in the retina, most sensitive to light around 500–600 nm (green).

L-cones

Long-wavelength photoreceptors in the retina, most sensitive to light around 600–700 nm (red).

RGB Color Model

Additive color system in which red, green, and blue light stimulate L-, M-, and S-cones to create all perceived colors.

Spectral Reflectance Curve

A graph showing the percentage of light a surface reflects at each wavelength, used to identify an object’s perceived color.

Absorbance vs. Reflectance

Absorbance is light energy taken in by a material; reflectance is light bounced off a surface and therefore visible to the eye.

Metamerism

The phenomenon where different combinations of wavelengths produce the same color perception due to cone responses.

Dichromacy

A type of color vision deficiency involving the absence or malfunction of one cone type, leaving two functional cones.

Protanopia

Red-green color blindness caused by absent or disrupted L-cones; reds appear dark, and red–green distinction is difficult.

Deuteranopia

Red-green color blindness caused by absent or disrupted M-cones; greens and reds are hard to distinguish.

Tritanopia

Blue-green color blindness (rare) caused by absent or disrupted S-cones; difficulty distinguishing blue from green.

Additive Color Mixing

Process of creating colors by combining light of different wavelengths; adding lights increases brightness toward white.

Cone Activation Pattern

The specific combination and strength of signals from L-, M-, and S-cones that the brain interprets as a particular color.

Black (in vision)

Perceived when no cones are activated because little or no light reaches the retina.

White (in vision)

Perceived when L-, M-, and S-cones are all strongly and roughly equally stimulated.

Spectrophotometer

Instrument that measures the amount of light reflected from or absorbed by a surface across wavelengths, producing reflectance curves.