The e-ILV provides free access to all the terms and definitions contained in the international standard CIE S 017:2020 ILV: International Lighting Vocabulary, 2nd edition.

To search for another term please use  "Back to the list" to return to the main page or the e-ILV.

For the complete set of terms and definitions CIE S 017:2020 can be purchased from the CIE Webshop. Members of a CIE National Committee or Associate National Committee have access to a 66,7 % discount on the purchase price of the standard.

For advice on CIE Publications contact Note the CIE Helpdesk cannot assist with technical enquiries.


radiance coefficient

qe; q

quotient of the radiance at a surface element of a medium in a given direction and the irradiance on the medium

where Le is radiance and Ee is irradiance

Note 1 to entry: The bi-directional reflectance distribution function (BRDF) is similar to the radiance coefficient except that it is defined for directional incident radiation.

Note 2 to entry: The radiance coefficient is expressed in steradian to the power minus one (sr−1).

Note 3 to entry: This entry was numbered 845-04-70 in IEC 60050-845:1987.

Note 4 to entry: This entry was numbered 17-1013 in CIE S 017:2011.

Publication date: 2020-12
Copyright © CIE 2020. All Rights Reserverd.