Mired on:
[Wikipedia]
[Google]
[Amazon]
Contracted from the term micro reciprocal degree, the mired is a unit of measurement used to express color temperature. Values in mireds are calculated by the formula:
:
where ''T'' is the colour temperature in units of kelvins and ''M'' denotes the resulting mired dimensionless number. The constant is one million kelvins.
For convenience, ''decamireds'' are sometimes used, with each decamired equaling ten mireds. The SI term for this unit is the reciprocal megakelvin (MK−1), shortened to ''mirek'', but this term has not gained traction.
The use of the term ''mired'' dates back to Irwin G. Priest's observation in 1932 that the just noticeable difference between two illuminants is based on the difference of the reciprocals of their temperatures, rather than the difference in the temperatures themselves.
A blue sky, which has a color temperature ''T'' of about , has a mired value of ''M'' = 40 mireds, while a standard electronic
Contracted from the term micro reciprocal degree, the mired is a unit of measurement used to express color temperature. Values in mireds are calculated by the formula:
:
where ''T'' is the colour temperature in units of kelvins and ''M'' denotes the resulting mired dimensionless number. The constant is one million kelvins.
For convenience, ''decamireds'' are sometimes used, with each decamired equaling ten mireds. The SI term for this unit is the reciprocal megakelvin (MK−1), shortened to ''mirek'', but this term has not gained traction.
The use of the term ''mired'' dates back to Irwin G. Priest's observation in 1932 that the just noticeable difference between two illuminants is based on the difference of the reciprocals of their temperatures, rather than the difference in the temperatures themselves.
Examples
A blue sky, which has a color temperature ''T'' of about , has a mired value of ''M'' = 40 mireds, while a standard electronic photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is emplo ...
flash, having a color temperature ''T'' of 5000 K, has a mired value of ''M'' = 200 mireds.
In photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is emplo ...
, mireds are used to indicate the color temperature shift provided by a filter or gel
A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still di ...
for a given film
A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmospher ...
and light source. For instance, to use daylight film (5700 K) to take a photograph under a tungsten light source (3200 K) without introducing a color cast
A colour cast is a tint of a particular colour, usually unwanted, that evenly affects a photographic image in whole or in part.
Certain types of light can cause film and digital cameras to render a colour cast. Illuminating a subject with light s ...
, one would need a corrective filter or gel providing a mired shift
:
This corresponds to a color temperature blue (CTB) filter.{{cite book , url=https://books.google.com/books?id=1JL2jFbNPNAC&q=ctb+159+mired&pg=PA172 , title=Cinematography: Theory and Practice : Imagemaking for Cinematographers , first=Blain , last=Brown , isbn=0-240-80500-3 , page=172 , publisher=Focal Press , year=2002
Color gels with negative mired values appear green or blue, while those with positive values appear amber or red.
References