Mired, Dekamired

Mired, derived from "micro reciprocal degree", is the reciprocal of color temperature multiplied by one millin:

Mired = 1 000 000 / Kelvin

In practice, decamireds are used as they are easier to work with:

Dekamired = Mired / 10

 

Color films are usually adapted to middle daylight of approx. 5600 K. They react to other sources of light not like the human eye, which makes an automatic "white alignment", but give the colors falsified. To avoid this, it is necessary to make a color adaption with a suitable conversion filter.

The necessary filter is calculated thereby as difference by the existing and the necessary color temperature. In the case of color films and artificial lighting the calculation is:

Mired value ( filter ) = Mired value ( film ) - Mired value ( light source )

Negative Mired values requires bluish ( KB = blue conversion filter ),
positive values a reddish color adaption ( KR = red conversion filter ).
 

The indices of the B+W conversion filters indicate the Dekamired value, for example KR 12 is a reddish conversion filter with a value of (+) 12 Decamired.

Those who prefer an easier method rather than performing computations can use the following figure to find the Kelvin- and Mired values for various light conditions and the correct filters for the color film that is being used. For example, a conversion filter KB 12 is needed for a daylight color film with halogen bulb lighting of  the motif.



Fig. 1: Nomograph to find out the ideal conversation filter