Grassmann's law (optics)

In the four Grassmann's laws of color theory of the " school teacher ", mathematician Hermann Günther Grassmann and Sanskritist (1809-1877) summed up his observations on the description and color mixing the colors together. The principles laid down by Grassmann laws applied largely to the additive color mixing, but are also fundamental in the subtractive color mixing.

The Grassmann's laws do not apply universally to all sighted creatures, but especially for the human sense of sight.

First graßmannsches law

Each color effect can be completely described by exactly three basic sizes.

Grassmann himself used it like the three basic sizes color ( spectral color ), color intensity and whiteness (today is this trinity known as the HSV color space ). The law is also in the three primary colors (such as the CIE primaries or RGB) applicable - just three colors can not be produced by a mixture of the other two in each case.

Second graßmannsches law

If you mix a color with a changing tone and a color in which the color remains the same, so colors occur with a changing hue.

This Grassmann describes in principle the (mathematical ) homogeneity of the color space - no matter which color change is carried out of a color, the mixed product follows analogously.

Third graßmannsches law

The hue of a created by additive color mixing color depends only on the color impression of the output colors from but not from its physical ( spectral ) compositions.

This law states that the mixing behavior of even the metameric colors - ie, those colors with the same color impression, but at the same time different spectral composition - can be accurately described purely because of their color impression. Conversely, so no direct conclusions on the spectral composition of a color can be drawn from the mixing behavior here.

Fourth graßmannsches law

The intensity of a color additively mixed corresponds to the sum of the intensities of output colors.

According to David L. MacAdam, this law applies only to the special case of point sources, but not for broader color space. Grassmann had dealt only with the special case mentioned above.

Grassmann was based his ideas on theories of Sir Isaac Newton and Hermann Ludwig Ferdinand von Helmholtz, which he but just in terms of a description in a color space significantly refined. The principles laid down by Grassmann laws were not as good as recognized for many years in the scientific world - but today they form a largely still valid basis of all modern color theories and spaces.