Instructions

HD2402 - 10 - V1.3
Similar definitions apply to photometry where irradiance will be replaced by illumi-
nance (lux) and radiance by luminance [cd/m
2
].
More generally, the link between any spectral radiometric quantity GR(
λ ) and the cor-
responding photometric quantity GF is given by the following formula:
∫
⋅⋅=
780
380
)()(683 λλλ dVGRGF
where :
V(λ) is the photopic vision curve (Figure 3), 380nm and 780nm are the integration ex-
tremes, out of these extremes V(λ)=0.
Figure 3: luminous efficacy curve for the photopic vision
The photopic vision curve represents the luminous efficacy of the human eye under
daylight conditions (in lowlight conditions, the response curve of the human eye
changes, and we talk about a scotopic vision).