Iv=dΦvdΩ
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:
Φv=∬.
Note 3 to entry: Luminous intensity can be derived from the spectral radiant intensity distribution by
I v = K m ∫ 0 ∞ I e,λ (λ)V(λ) dλ MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeea0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaaciWacmGadaGadeaaeaGaauaaaOqaaa baaaaaaaaapeGaamysamaaBaaaleaacaqG2baabeaakiabg2da9iaa cckacaWGlbWaaSbaaSqaaiaab2gaaeqaaOWdamaapehabaWdbiaadM eadaWgaaWcbaGaaeyzaiaabYcacqaH7oaBaeqaaOWdaiaacIcapeGa eq4UdW2daiaacMcapeGaamOva8aacaGGOaWdbiabeU7aS9aacaGGPa GaaGPaV=qacaqGKbGaeq4UdWgal8aabaGaaGimaaqaaiabg6HiLcqd cqGHRiI8aaaa@51FF@
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.
I v = d Φ v dΩ MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadMeadaWgaaWcbaGaaeODaaqabaGccqGH9aqpdaWcaaqaaiaabsgacqqHMoGrdaWgaaWcbaGaaeODaaqabaaakeaacaqGKbGaeuyQdCfaaaaa@3E68@
Φv=∬ΩIv(ϑ,φ)sinϑ dφ dϑMathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeea0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaaciWacmGadaGadeaaeaGaauaaaOqaai abfA6agnaaBaaaleaacaqG2baabeaakiabg2da9maapifabaGaamys amaaBaaaleaacaqG2baabeaakmaabmaabaGaeqy0dOKaaiilaiabeA 8aQbGaayjkaiaawMcaaiaabohacaqGPbGaaeOBaiabeg9akjaabcca caqGKbGaeqOXdOMaaeiiaiaabsgacqaHrpGsaSqaaiabfM6axbqab0 Gaey4kIiVaey4kIipaaaa@52FC@.