SPECTRAL REFLECTANCE OF NATURAL OBJECTS - HOW MANY BASIS FUNCTIONS ARE NECESSARY

Ideal-observer analysis was used to determine the number of basis functions necessary to represent the spectral reflectances of natural objects. The ideal observer was placed at the level of photon catch in the foveal photoreceptors of a typical human eye. Daylight illumination was used. Discrimination of an original reflectance spectrum from its approximation typically reached an asymptote after three or four basis functions were used. A consideration of various factors involved in real rather than ideal performance led to the conclusion that three basis functions are necessary and probably sufficient for representing the spectral reflectance functions of natural objects.