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Colour temperature

Describes the colour of a light source, measured in Kelvin. The physical measurement uses Planck's (black) radiator, a highly heatable black cavity whose radiation escapes through a small opening.


The spectral radiation distribution is determined and the corresponding temperature in Kelvin. The emitter passes through different colour levels at different temperatures, so that colours can be assigned to the temperatures.

If it emits red light, the temperature is 2000 K, 5000 K for white light and 10,000 K for blue light. At a certain colour temperature of a light source, the colour is identical to the same temperature of the black radiator (but not necessarily the same spectral radiation distribution).

For colour matching, standard light types that correspond to a certain colour temperature, e.g. D50, D60, are recommended.