# e-ILV

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.

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# 17-21-039

luminous flux

Φv; Φ

change in luminous energy with time

where Qv is the luminous energy emitted, transferred or received, and t is time

Note 1 to entry: Luminous flux is a quantity derived from the radiant flux, Φe, by evaluating the radiation according to its action upon the CIE standard photometric observer. Luminous flux can be derived from the spectral radiant flux distribution by

where Km is maximum luminous efficacy, Φe,λ(λ) is spectral radiant flux, V(λ) is spectral luminous efficiency and λ is wavelength.

Note 2 to entry: The distribution of the luminous intensities as a function of the direction of emission, e.g. given by the polar angles (ϑ, φ), is used to determine the luminous flux, Φv, within a certain solid angle, Ω, of a source:
.

Note 3 to entry: The corresponding radiometric quantity is "radiant flux". The corresponding quantity for photons is "photon flux".

Note 4 to entry: The luminous flux is expressed in lumen (lm).

Note 5 to entry: This entry was numbered 845-01-25 in IEC 60050-845:1987.

Note 6 to entry: This entry was numbered 17-738 in CIE S 017:2011.

Publication date: 2020-12