primary colors of light

Light color is the color of the light emitted by a lamp. Light color can be expressed using x,y coordinates as chromacity coordinates in a standard colorimetric system, or, for white light colors, it can also be given as the color temperature TF . In the CIE standard colorimetric system, the color of light is calculated from the spectral constitution and represented in a continuous, two-dimensional diagram. The hue is defined via the chromaticity co-ordinates of the spectral color and via the saturation level. The design of the diagram features a colored area that contains every possible real color. The coloured area is encompassed by a curve on which the chromaticity locations of the completely saturated spectral colors lie. At the centre of the area is the point of least saturation, which is designated as a white or uncolored point. All levels of saturation of one color can now be found on the straight lines between the uncolored point and the chromaticity location in question. Similarly, all mixtures of two colors are likewise to be found on a straight line between the two chromaticity locations in question.

Closest color temperature

Planck’s curve contains the chromaticity locations of Planck’s radiation of all temperatures. Since the chromaticity location of a light source often lies near to the curve, starting from the curve of Planck’s radiator, a host of straight lines of the closest color temperatures is added. With their help, even those light colors that are not on this line can be identified by the closest color temperature. On temperature radiators, the closest color temperature corresponds to something approaching the actual temperature of the lamp filament. On discharge lamps, the closest color temperature is stated.

Main groups color temperatures

In addition, white colors of light are divided into three main groups: the warm white range (ww) with the closest color temperatures below 4000 K, the neutral white range (nw) between 4000 and 5000 K and the daylight white range (dw) with the closest color temperatures over 5000 K. The same colors of light may have different spectral distributions and a correspondingly different color rendition

Color rendition

Color rendition refers to the quality of the reproduction of colors under a given illumination. The degree of Color distortion is indicated using the Color rendition index Ra and/or the color rendition grading system. A comparative light source with continuous spectrum serves as a reference light source, whether this be a temperature radiator of comparable color temperature or the daylight.


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