${\displaystyle V=\frac{{\displaystyle {\int }_0^{\infty }{\Phi }_{\text{e,}\lambda }\left(\lambda \right)\cdot V\left(\lambda \right)\cdot \text{d}\lambda }}{{\displaystyle {\int }_0^{\infty }{\Phi }_{\text{e,}\lambda }\left(\lambda \right)\cdot \text{d}\lambda }}=\frac{K}{K_{\text{m}}}}$

unit : 1

NOTE 1 - For the spectral luminous efficiency, ${\displaystyle V\left(\lambda \right)=\frac{K\left(\lambda \right)}{K_{\text{m}}}}$ see 845-01-22.

NOTE 2 – For scotopic vision, the symbols in the formulae are replaced by V′, Φ′, K′ and K′_m respectively.