Standard illuminant
![Relative spectral power distributions (SPDs) of CIE illuminants A, B, and C from 380nm to 780nm.](/Images/godic/202502/13/CIE_illuminants_A,B,C.svg1244.png")
![](/Images/godic/202502/13/CIE_illuminants_D_and_blackbody_small1244.gif")
![Characteristic vectors of illuminant D; component SPDs S0 (blue), S1 (green), S2 (red).](/Images/godic/202502/13/CIE_illuminants_D_components.svg1244.png")
![](/Images/godic/202502/13/Daylight-locus-in-CIE-1960-UCS1244.png")
A standard illuminant is a theoretical source of visible light with a profile (its spectral power distribution) which is published. Standard illuminants provide a basis for comparing images or colors recorded under different lighting.