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

${\displaystyle V=\frac{{\displaystyle \underset{0}{\overset{\infty }{\int }}{\Phi }_{\text{e},\lambda }(\lambda )V(\lambda )\text{d}\lambda }}{{\displaystyle \underset{0}{\overset{\infty }{\int }}{\Phi }_{\text{e},\lambda }(\lambda )\text{d}\lambda }}=\frac{K}{K_{\text{m}}}}$

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.