Mired


Mired
Close up of the Planckian locus in the CIE 1960 color space, with the isotherms in mireds. Note the even spacing of the isotherms when using the reciprocal temperature scale. The even spacing of the isotherms on the locus implies that the mired scale is a better measure of perceptual color difference than the temperature scale.
Close up of the Planckian locus in the CIE 1960 color space, with the isotherms in kelvins. The range of isothermal color temperatures, as in the previous diagram, is from 1000 K (1000 MK-1) to 10,000 K (100 MK-1).

Contracted from the term micro reciprocal degree, the mired is a unit of measurement used to express color temperature. It is given by the formula:

M=\frac{1000000}{T}

where M is the mired value desired, and T is the color temperature in kelvins.

For convenience, decamireds are sometimes used, each decamired containing 10 mireds. The SI unit is the reciprocal megakelvin (MK−1), shortened to mirek, but this term has not gained traction.[1]

Its use dates back to Irwin G. Priest's observation in 1932 that the just noticeable difference between two illuminants is based on the difference of their reciprocal temperatures, rather than the difference in the temperatures themselves.[2]

Examples

A blue sky, which has a color temperature T of about 25,000 K, has a mired value of M=40 mireds, while a standard electronic photography flash, having a color temperature T of 5000 K, has a mired value of M=200 mireds.

In photography, mireds are used to indicate the color temperature shift provided by a filter or gel for a given film and light source. For instance, to use a tungsten light (3200 K) in natural light (say, 5700 K) without introducing a color cast, one would need a corrective filter or gel providing a mired shift of

\frac{10^6}{5700} - \frac{10^6}{3200} \approx -137\ \mbox{MK}^{-1}

This corresponds to a CTB (color temperature blue) filter.[3]

References

  1. ^ Ohta, Noboru; Robertson, Alan R. (2005). Colorimetry: Fundamentals and Applications. Wiley. p. 84. ISBN 0470094729. 
  2. ^ Priest, Irwin G. (February 1932). "A proposed scale for use in specifying the chromaticity of incandescent illuminants and various phases of daylight" (abstract). JOSA 23 (2): 41–45. doi:10.1364/JOSA.23.000041. http://www.opticsinfobase.org/abstract.cfm?URI=josa-23-2-41. 
  3. ^ Brown, Blain (2002). Cinematography: Theory and Practice : Imagemaking for Cinematographers. Focal Press. p. 172. ISBN 0240805003. http://books.google.com/?id=1JL2jFbNPNAC&pg=PA172&lpg=PA172&dq=ctb+159+mired. 

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  • Mired — deriva del inglés micro reciprocal degree (microgrado recíproco). El Mired (M) es una unidad de medida equivalente a 1.000.000 (un millón) dividido por la temperatura de color dada, según la fórmula: donde M es el valor mired deseado y K es la… …   Wikipedia Español

  • mired — [miʀɛd] n. m. ÉTYM. Av. 1976; mot angl., de mi(cro) re(ciprocal) d(egree). ❖ ♦ Photogr. Unité de température de couleur, égale à l inverse d un millionième de degré Kelvin (1 mired = ). || Le mired est utilisé en photographie pour évaluer le… …   Encyclopédie Universelle

  • mired — [maıəd US maırd] adj [not before noun] literary 1.) stuck in a bad situation and unable to get out or make progress mired in ▪ a government mired in scandal and controversy 2.) stuck in mud or covered in mud …   Dictionary of contemporary English

  • Mired — Farbtemperatur in K Farbtemperatur in Mired …   Deutsch Wikipedia

  • Mired — Gros plan sur le lieu planckien représenté dans l espace couleur CIE 1960, avec les isothermes en kelvin. Les isothermes se succèdent à intervalles irréguliers, de 1000 K à 10000 K …   Wikipédia en Français

  • Mired — Mire Mire, v. t. [imp. & p. p. {Mired} (m[imac]rd); p. pr. & vb. n. {Miring}.] [1913 Webster] 1. To cause or permit to stick fast in mire; to plunge or fix in mud; as, to mire a horse or wagon. [1913 Webster] 2. Hence: To stick or entangle; to… …   The Collaborative International Dictionary of English

  • mired — adj. to get mired (in the mud) * * * to get mired (in the mud) …   Combinatory dictionary

  • mired — UK [maɪə(r)d] / US [maɪrd] adjective 1) caught in an unpleasant situation that you cannot easily escape from people mired in poverty 2) stuck in soft wet ground …   English dictionary

  • mired — adjective entangled or hindered as if e.g. in mire the difficulties in which the question is involved brilliant leadership mired in details and confusion • Syn: ↑involved • Similar to: ↑encumbered …   Useful english dictionary

  • mired — maɪə(r) n. area of swampy land, marsh, bog; mud, muck v. muddy; become stuck in mud; become involved in difficulties, get in trouble …   English contemporary dictionary


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