Understanding Color, 5th Edition

2 A LITTLE LIGHT ON THE SUBJECT Light / Additive Color: Mixing Light / Lamps / Lamp Types / Special Purpose Lamps / False Promise: Full-Spectrum Lighting / Lighting Level / Vision / The Illuminant Mode of Vision / The Object Mode of Vision / Modifying Light: Colorants / Lamps and Color Rendition / The Color Rendering Index / Metamerism and Matching / Modifying Light: Surface / Transparent, Opaque, and Translucent / Iridescence / Luminosity / Indirect Light, Indirect Color / Filters

Colors seen by candlelight

Will not look the same by day.

—Elizabeth Barrett Browning, “The Lady's Yes,” 1844

Color is a visual experience, a sensation of light that cannot be verified by any other sense—not by touch, taste, smell, or hearing. A colored object can be touched, but it is the object itself that is tangible, not its color. Color has no physical substance. It is light alone.

There are two pathways to color perception: colors seen as direct light, and the colors of objects. Colors made of light can be controlled so that they are unvarying, but the colors of objects are unstable. Almost everyone has experienced buying an article of clothing and arriving home to find that it is a different color than it seemed in the store, or selecting a paint color and being startled by the result on the wall. Even the idea of a color can be unstable. Perception is a complicated experience that includes not only what is seen but also how it is understood. A number of people looking at the same color—whether ...