A color is defined by the threefold combination “source-object-observer.”

  • Source: reference illuminant with a relative spectral energetic distribution .

  • Object: in general opaque, with a diffuse reflectance .

  • Observer: normalized by the CIE in 1931 (vision field of 2°) and later in 1964 (vision field of 10°) with the colorimetric functions , and .

This leads to the following trichromatic components , and :

By convention the scaling factor is defined by:

Notwithstanding the “color atlas” that one may use in order to visually compare colors, all colorimetry systems based on photoelectric measurements are based on the calculation of the trichromatic components , and derived from (19).

The main manufacturers of colorimetric measurement systems are Hunterlab and Gretag Macbeth. Other companies are now commercializing such systems, like Minolta, Zeiss or X-rit. Datacolor International is specialized in color control tools for textiles.

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