A luminosity function or common Sensibles PDF efficiency function describes the average spectral sensitivity of human visual perception of brightness. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. There are two luminosity functions in common use.
Författare: Theodor Loewy.
For everyday light levels, the photopic luminosity function best approximates the response of the human eye. For low light levels, the response of the human eye changes, and the scotopic curve applies. The photopic curve is the CIE standard curve used in the CIE 1931 color space. Formally, the integral is the inner product of the luminosity function with the power spectral density. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function. This arbitrary number made the new definition give numbers equivalent to those from the old definition of the candela.
There have been numerous attempts to improve the standard function, to make it more representative of human vision. The standard provides an incremental table by nm of each value in the visible range. For comparison, the standard photopic curve is shown in yellow. Color blindness changes the sensitivity of the eye as a function of wavelength. Most non-primate mammals have the same luminosity function as people with protanopia.