8. Glossary of photometric quantities

Photometric quantities Characterize light by its ability to stimulate visual sensation in the average person. The relative spectral luminous efficacy V (λ), given in figure 31 , illustrates the variations in sensitivity of the human eye in daylight vision, as a function of the wavelength considered. Maximum sensitivity is reached at 555 nm, corresponding to the color green-yellow. In layman's terms, photometric quantities are the energy quantities "filtered" by the eye's sensitivity V(λ).