Section 6 | Page 7

Color Space Models

Early attempts to map visible color date back to the middle 1800s. Over the years, several color space models have been proposed. Most color space models, however, define colors in three dimensions and provide a scheme for representing color in terms of three coordinates. Color space models differ in the same way a city map with one set of grid coordinates differs from another map of the same city that uses a different set of grid coordinates.

The color space model proposed in 1931 by the International Commission of Illumination, known as the CIE, is generally accepted as the world standard for the measurement of color.

The CIE color model is based on the measurement of human color perception. This model of color space is not symmetrical along the vertical axis. At the midpoint of the vertical, or lightness, axis, the CIE model is not circular but horseshoe-shaped.

A symmetrical model of color space called CIELAB, proposed in 1976, has become the accepted standard for the graphic arts industry. The CIE and CIELAB models use the same spectrophotometric measurements, but use different mathematical equations to map three-dimensional color space.

See Figure