Measured in Kelvin. The colour temperature describes the perceived colour impression of a light source.
For example, a lamp with 3000K is perceived as warm light and one with 6000K as cold light.
Our D50 standard light has a colour temperature of 5000K.
A standardized light is called a defined light condition under which the viewer can view and assess prints or objects uniformly. The most important standard illuminants D50 are in accordance with ISO 3664:2009 for printmaker and for colour matching in prepress and press (colour temperature: 5,000 kelvin) and D65 (colour temperature: 6500 K) for internet graphic designer. D65 is the default setting for most monitors.
Other important types of light are TL84, the standard neon light (colour temperature: 4,100 kelvin), which dominates factories and supermarkets, and A – incandescent light (light bulb) with a colour temperature of 2,700 Kelvin.