Chromaticity limits in color constancy calculations

Abstract

There are two very different kinds of color constancy. One kind studies the ability of humans to be insensitive to the spectral composition of scene illumination. The second studies computer vision techniques for calculating the surface reflectances of objects in variable illumination. Camera-measured chromaticity has been used as a tool in computer vision scene analysis. This paper measures the ColorChecker test target in uniform illumination to verify the accuracy of scene capture. We identify the limitations of sRGB camera standards, the dynamic range limits of RAW scene captures, and the presence of camera veiling glare in areas darker than middle gray. Measurements of scene radiances and chromaticities with spot meters are much more accurate than camera capture due to scene-dependent veiling glare. Camera capture data must be verified by calibration.