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.


spherical illuminance

Ev,o; Eo

mean value of illuminance on the outer curved surface of a very small (real or imaginary) sphere at a point in space

Note 1 to entry: The spherical illuminance can be expressed by

where Ω is solid angle and Lv is luminance.

Note 2 to entry: The spherical illuminance is the quotient of the luminous flux of all the light incident on the outer surface of an infinitely small sphere centred at the given point and the area of the diametrical cross-section of that sphere.

Note 3 to entry: The analogous quantities "spherical irradiance", Ee,o, and "photon spherical irradiance" (also termed "photon fluence rate"), Ep,o, are defined in a similar way, replacing luminance, Lv, by radiance, Le, and photon radiance, Lp, respectively.

Note 4 to entry: The spherical illuminance is expressed in lux (lx = lm·m−2).

Note 5 to entry: This entry was numbered 17-1244 in CIE S 017:2011.

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