The Mired value (mrd) is a dimensionless (1/Kelvin) value used to indicate color temperatures and color shifts. It refers to the color temperature specified in Kelvin and shows the shift of a color temperature towards higher or lower color temperatures.
Each color temperature is assigned a micro-reciprocal value; this is the reciprocal of the color temperature multiplied by 1 million, or, in other words, 1 million divided by the color temperature. For example, a color temperature of 5,500 Kelvin has a Mired value of 182, and one of 3,600 Kelvin has a Mired value of 278.
In studio recording, conversion filters are used to shift the color temperature by a certain Mired value. This value can be used to determine by how many degrees Kelvin the color temperature is shifted by a corresponding film filter.
In addition to the Mired value, there is also a decimal classified Mired value, the Decamired value( DM), which is lower than the Mired value by two powers of ten. Films, lights and color filters have DM values. If the DM value of the light source and that of the film are known, the DM value of the filter can be determined by subtracting both.