ReferenzIlluminants

ReferenzIlluminants, or reference illuminants, are standardized spectral power distributions used as reference sources for color measurement and reproduction. They provide a reproducible white point and a basis for comparing colors across devices, media, and viewing conditions. These reference light sources are defined by international standards organizations such as the CIE (International Commission on Illumination) and ISO, and they describe how colors should appear under known, controlled lighting.

Common examples include Illuminant A, which represents a typical tungsten/incandescent light; Illuminant D65, representing average daylight around 6500 Kelvin; Illuminant D50, used frequently in printing and prepress workflows around 5000 Kelvin; and Illuminant E, a neutral equal-energy spectrum. The D-series are particularly important in color management, with D65 serving as the standard white point for many color spaces (such as sRGB) and display calibration routines, while D50 is favored in the printing industry.

In practice, reference illuminants underpin device calibration, white balance settings, and colorimetric calculations. They define the spectral power distribution and, together with a standard observer, enable chromatic adaptation, color matching, and the construction of ICC profiles. They are idealized references and do not capture all real-world lighting conditions, which can vary and cause metamerism where colors match under one light but not another. Nevertheless, reference illuminants remain foundational for consistent color reproduction across imaging, printing, and viewing environments.