luminous efficiency, <for a specified photometric condition>

V, <for photopic vision>; V′, <for scotopic vision>; V_mes;m , <for mesopic vision>; V₁₀ , <for the CIE 10° photopic photometric observer>; V_M , <for the CIE 1988 modified 2° spectral luminous efficiency function for photopic vision>

quotient of radiant flux weighted by the spectral luminous efficiency and the corresponding radiant flux for a specified photometric condition

Note 1 to entry: The photometric condition should be specified (e.g. photopic, scotopic, mesopic). If it is not specified, photopic vision is assumed and the symbol V is used. For other photometric conditions the respective symbol for identification shall be used.

Note 2 to entry: Luminous efficiency for photopic vision is expressed by

where Φ_e,λ is spectral radiant flux, V(λ) is spectral luminous efficiency, λ is wavelength, K is luminous efficacy of radiation, and K_m is maximum luminous efficacy.

Note 3 to entry: The luminous efficiency has unit one.

Note 4 to entry: This entry was numbered 845-01-57 in IEC 60050-845:1987.

Note 5 to entry: This entry was numbered 17-731 in CIE S 017:2011.