Tri and tetrachromatic metamerism

Two light beams that are seen of the same colour and possibly having different spectra are said to be metameric. The colour of a light beam is based on the reading of severel photodetectors with different spectral responses and metamerism results when a set of photodetectors is unable to resolve two spectra. From a mathematical point of view, metamerism can be characterized in terms of the L, M and S responses of the retina, in terms of the CIE X, Y and Z curves, etc. . We are interested in exploring the concept of metamerism both in the trichromatic and in the tetrachromatic cases. Applications are in computer vision, computational photography and satellite imaginery, for example. We make a case for chromatic metamerism, when the luminance is different and also hue metamerism when both the luminance and the saturation are different.