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Grassmann Laws

The basic laws for additional colors and color-matching experiments were established by Grassmann (1853), who attributed many of his ideas to Maxwell. The laws Grassmann developed from these experiments state the following:

1. To specify a color, three elements are necessary and sufficient: the hue, the luminance, and the luminance of the intermixed white, which defines the saturation.
2. For every color, there is complementary color, which, when mixed, becomes a colorless gray.
3. Two lights of different color with the same hue and saturation, when mixed, produce another color with identical hue and saturation independently of their power spectra.
4. The total luminance of any mixture of light is the sum of each light's luminance.

These laws are the basis of all mathematical procedures established in colorimetry. However, some important conditions must be considered:

1. All color matches must be made under similar conditions.
2. The eye's previous exposure to light affects the state of adaptation, influencing the spectral sensitivity of the eye.
3. If a field diameter larger than 10 deg is used in a color match, a failure of the proportionality law may be found.