# 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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# 17-21-045

luminous intensity

Iv; I

density of luminous flux with respect to solid angle in a specified direction

where Φv is the luminous flux emitted in a specified direction, and Ω is the solid angle containing that direction

Note 1 to entry: For practical realization of the quantity, the source is approximated by a point source.

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: Luminous intensity can be derived from the spectral radiant intensity distribution by

where Km is maximum luminous efficacy, Ie,λ(λ) is the spectral radiant intensity at wavelength λ, and V(λ) is spectral luminous efficiency.

Note 4 to entry: The corresponding radiometric quantity is "radiant intensity". The corresponding quantity for photons is "photon intensity".

Note 5 to entry: The luminous intensity is expressed in candela (cd = lm·sr−1).

Note 6 to entry: This entry was numbered 845-01-31 in IEC 60050-845:1987.

Note 7 to entry: This entry was numbered 17-739 in CIE S 017:2011.

Publication date: 2020-12