Glossary

The words these notes use, each in a sentence or two, with a link to the lesson that explains it.

Each term links to the lesson where it is explained properly.

Absorption: Light a pigment takes in and turns into a little heat. A pigment’s color comes from which wavelengths it absorbs and which it lets go. Section 2.1
Adaptation: The eye’s adjustment to the light it is in, which is why a white sheet looks white under a tungsten bulb and in the shade of a blue sky. Section 1.5
Calibrated paints: The 26 Golden paints whose mixtures with white Okumura measured. They are the only paints the model mixes. Section 2.6
Chroma: How vivid a color is, compared with a gray of the same lightness and judged against a white in the same light. Written \(C^*\) in CIELAB. Section 1.6
Chromaticity diagram: A map of color with the amount of light taken out. The single wavelengths lie around its curved edge, white sits near the middle, and a mixture of two lights lies on the straight line between them. Section 1.7
CIELAB: The standard color coordinates used in these notes: lightness, and two color coordinates running from green to red and from blue to yellow. Chroma and hue angle come from those two. Section 1.7
Colorfulness: How much color something seems to have. It grows with the light falling on it; chroma is colorfulness judged against a white. Section 1.6
Cones: The three kinds of light-sensitive cell in the eye that see color, called L, M and S after the long, middle and short wavelengths they respond to most. Section 1.2
Glaze: A thin layer of transparent paint over a lighter ground, which the light crosses on its way in and again on its way out. Section 3.6
Hue: Whether a color looks red, yellow, green, blue or something in between. In CIELAB it is an angle around the color circle. Section 1.6
Illuminant: A light described by how much it gives at each wavelength, such as the CIE’s standard daylight (D65) or a tungsten bulb (illuminant A). Section 1.1
K/S: A paint’s absorption divided by its scattering, at each wavelength. In a layer too thick to see through, this ratio alone decides how much light comes back. Section 2.1
Kubelka–Munk law: The rule that turns K/S into the share of light a thick layer reflects, by following one flux of light going down and one coming up. Section 2.1
Lean (or bias): The neighboring hue a paint tilts toward, such as a red that leans toward orange or toward violet. Section 3.8
Lightness (or value): How light a color looks compared with a white in the same light, from 0 for black to 100 for white. Written \(L^*\) in CIELAB. Section 1.6
Masstone: The paint straight from the tube, in a layer too thick to see through. Section 1.1
Metamers: Two colors with different reflectance curves that match under one light. Under another light they can come apart. Section 1.4
Mixing complement: The paint that mixes with a given paint to gray, or as near gray as the palette allows. It is often a different paint from the visual complement. Section 3.9
Mixing line: The series of colors between two paints, mixed in steps from all of one to all of the other. Section 3.1
Opacity: How well a paint covers what lies under it. It comes mostly from scattering. Section 2.4
Opponent channels: The eye’s red-green and yellow-blue signals, made by comparing the cones. They are why no color looks reddish green or yellowish blue. Section 1.3
Primary: On the palette, a paint that nothing else there can mix. Section 4.1
Reflectance curve: The share of light a surface sends back at each wavelength. It is the physical fact behind a surface’s color. Section 1.1
Saturation: Colorfulness judged against the color’s own brightness, so it needs no white beside it. Section 1.6
Scattering: Light turned aside by pigment particles without being absorbed. Scattering sends light back out of the paint and gives a paint its hiding power. Section 2.1
Surface reflection: The few percent of light that bounces off the top of the paint without going in. It sets a floor under how dark a measured paint can read. Section 2.2
Tint: A paint mixed with white. Section 1.1
Tint ladder: A series of mixtures of one paint with more and more white. The model in these notes is built on Okumura’s measured ladders. Section 2.6
Tinting strength: How far a gram of paint goes in a mixture. Section 3.1
Transparent paint: A paint whose particles scatter little, so light passes through it to whatever lies beneath. Section 2.4
Unique hues: The four hues that look like nothing but themselves: red, yellow, green and blue. Section 1.3
Unit of color difference: About the smallest difference between two colors a careful observer can see side by side. Written \(\Delta E_{00}\) in the figures. Section 1.7
Visual complement: The hue directly across the color circle, the one the eye’s color channels treat as opposite. Section 4.7
Wavelength: The length of a light wave, measured in nanometers (millionths of a millimeter). On its own, light of one wavelength has one color. Section 1.1