CIE

(Commission Internationale de l'Eclairage, International Commission on Illumination, Vienna, Austria, www.cie.co.at) An international organization that sets standards for all aspects of lighting and illumination, including colorimetry, photometry and the measurement of visible and invisible radiation.

In 1931, CIE defined a color space that represents all possible colors in a 2D chromaticity diagram. CIE Lab added a third dimension of luminance (L), and color is based on the values in the red-green axis (a) and blue-yellow axis (b). CIE Lab is officially expressed as "CIE L*a*b*."

A Reference and Intermediary
Although CIE Lab has a large color gamut and is considered the most accurate color model, it is often used as a reference only or as an intermediary for color space conversion. In practice, the RGB and CMYK color spaces are more widely used for display and printing. In the original model, the color green seemed to dominate the diagram. In 1960 and 1976, improvements were made that displayed all colors more uniformly. See color space.

The 1976 Chromaticity Diagram

The 1976 CIE model shows a more uniform distribution of perceived colors across the model than the original 1931 diagram. (Image courtesy of Photo Research, Inc., www.photoresearch.com)