IEVref:845-04-69ID:
Language:enStatus: Obsolete
Term: luminance factor (at a surface element of a non-self-radiating medium, in a given direction, under specified conditions of illumination)
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Symbol: βv
β
Definition: ratio of the luminance of the surface element in the given direction to that of a perfect reflecting or transmitting diffuser identically illuminated

unit : 1

NOTE 1 – For photoluminescent media, the luminance factor is the sum of two portions, the reflected luminance factor βs and the luminescent luminance factor βL : βv = βS + βL.

NOTE 2 – In Germany, instead of the luminance factor β (or transmittance τ) it is usual in colorimetry to use the quantity "Hellbezugswert" A = 100 β (or 100 τ).


Publication date:1987
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Internal notes:2012-07-17: <br> added in Symbol field as an example to discuss with Jean Schwob. JGO
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