Chromaticity

Chromaticity ( conspecific colors) referred to in colorimetry, the grouping of colors by hue and saturation, but with different brightness. Depending on the application level, the chromaticity based on different colors or primary colors.

Basic

This term is defined basing it in DIN 5033 and in CIE 845-03-34.

A color is uniquely identified by three parameters according to the Grassmann laws. A color stimulus is analyzed by the three types of cones in the eye. This will be " filtered out " from the continuous spectrum three valences. The physical cause of the color perception of the plurality of values ​​, the intensities on the wavelengths. General named with the following symbols: β ( λ ) for remission of body colors, τ ( λ ) for transmission of filters, σ ( λ ) with light colors. It is through the sense of sight, a three number of sensations which processes in the nervous system give the impression of color. These three parameters can be represented in different ways in a three dimensional color space.

Depending on the application level or the perception category, the chromaticity is based on three primary colors, the color stimuli of the three-color theory (red, green, blue) or in four contrasting colors of the opponent color theory (red-green and yellow-blue ). The achromatic remain assessed only indirectly.

The color space may be chosen so that the brightness of its own axis associated with it. The remaining coordinates then pass to the chromaticity. The brightness can also be viewed as lightness value A or neutral gray value.

In CIEXYZ color system, the xy color plot is calculated as ( chromaticity diagram ). In the L * a * b * color space of the CIE 1976 chromaticity system in the a *-b * plane is given. Where a * is a green-red and the b * axis for the blue-yellow - values ​​. This form of color representation offers the advantage that a the familiar color circle corresponding indication is possible. These chromaticity coordinates in the Cartesian system can be divided into polar coordinates C h ° ( Chroma, Hue ) transform, that respond to the inexperienced and thus more practical understanding of color and match the color wheel.

In the RGB color space and the CMYK color space of the representation of the chromaticity does not make sense, since the emission colors of the three phosphors, the three color filters or in the CMYK space, the three color pigments was applied. The fourth color pigment K (black) according to the definition in this case is merely a supplement to achieve "deep ". In both color spaces brightness is not the immediate parameters and the chromaticity is thus placed over the entire room.

Color Trio

Since the late Middle Ages is common among painters, a mixing rule of three primary colors. Also for technical equipment and procedures is the use of three color sources is largely sufficient. In the color picture tube, these are the three RGB phosphors of red, green and blue. Just as the CMY colors form a color trio. The color trio goes back to research of the Englishman James Sowerby, of his work dedicated to Isaac Newton A New Elucidation of Colours, published in 1809. Sowerby was firstly emphasize the importance of light and darkness, on the other hand point out once again that differ colored light and colored matter in their behavior.

Sowerby went out of the three primary colors red, yellow, blue in its investigations.

Upon further investigation of the relationships of color perception Herring added, with its four-color theory still green. The Englishman Thomas Young introduced in its investigations and the resulting theory, the "theory of trichromatic vision," in turn, states that the eye combines already by the perception of three color quality tones all other valences. But Young put based red, green and blue, and replaced by Sowerby Yellow Green.

In the 20th century, the Young's theory was deepened experimentally. The pigments in the cones on the retina may very well perceive red, green or blue light. On the other hand, the psychological processes of color perception in particular, led the role of visual brightness and chromaticity to clarify the relationship with the opponent colors theory.