Mired

Contracted from the term micro reciprocal degree, the mired is a unit of measurement used to express <a href="/facts/Color_temperature/g77MjsPM">color temperature</a>. Values in mireds are calculated by the formula:

M
        =
        
          
            
              1
              
              000
              
              000
              
              
                K
              
            
            T
          
        
        ,
      
    
    {\displaystyle M={\frac {1\,000\,000\,{\text{K}}}{T}},}

where T is the colour temperature in units of <a href="/facts/Kelvin/E3trzC4C">kelvins</a> and M denotes the resulting mired dimensionless number. The constant 1000000 K is one million kelvins.
The <a href="/facts/SI/NShmfzlD">SI</a> term for this unit is the reciprocal megakelvin (MK−1), shortened to mirek, but this term has not gained traction.
For convenience, decamireds are sometimes used, with each decamired equaling ten mireds.
The use of the term mired dates back to Irwin G. Priest's observation in 1932 that the <a href="/facts/Just_noticeable_difference/r3KeemTF">just noticeable difference</a> between two <a href="/facts/Illuminant/urST5Mz7">illuminants</a> is based on the difference of the <a href="/facts/Multiplicative_inverse/yczdYyCw">reciprocals</a> of their temperatures, rather than the difference in the temperatures themselves.

Mired open-in-new

Mired