color temperature (CT)
For comparability of colors and for the purpose of color mixing, the spectral characteristic of light is expressed as color temperature in Kelvin (K). The Kelvin scale ranges from artificial light, the long-wave light, which is at Kelvin values of 3,200 K, through daylight to blue, a short-wave light, of 10,000 K.
Theoretically, the color temperature corresponds to the wavelength that an ideal black body would emit when heated to the corresponding temperature.
The white light standard, which is the standard light for the printing industry, has 5,000 K (D50). In the CIE color space, this white has xy coordinates of 0.3457/0.3585. The color temperature for daylight depends on the amount of sunlight. Normal daylight has a color temperature of 5,000 K (D50), while it is 6,500 K in the midday sun. The CIE designation for this type of light is standard illuminant D65 and has xy coordinates 0.312713/0.329016.
This value is ideal for projector lamps, because at this color temperature the projected colors are displayed most naturally. For simple monitors, color temperature values of 9,300 K are sometimes used, but this limits the color representation.
White light in lighting technology is also specified according to an international color designation. A distinction is made between incandescent white, warm white, neutral white and daylight white, whose color temperatures form the second and third digits of the international color designation.
In studio and film technology, the reciprocal color temperature is used; the value determined from this is called the Mired value.