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Sérgio Nascimento, Paulo Felgueiras, Joäo Linhares; Color rendering and the spectral structure of the illuminant. Journal of Vision 2010;10(7):401. doi: 10.1167/10.7.401.
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© ARVO (1962-2015); The Authors (2016-present)
The increasing availability of light sources with almost arbitrary spectral distributions, like LED and DLP based sources, poses the problem of selection of a specific spectral profile. To this effect the relationships between spectral structure and the visual effects over rendered scenes need to be taken into consideration, a matter that has not been quantified systematically. In this work we addressed this issue by studying, computationally, the chromatic effects of a large set of illuminants with almost arbitrary spectral structure. The illuminants were metamers of a Plankian radiator with color temperature of 6500 K and metamers of non-Plankian radiators with chromaticity coordinates uniformly distributed over the same isotemperature line. The metamers were generated by the Schmitt's elements approach and were parameterized by the spectral distance to the equi-energy illuminant E and by the number of non-zero spectral bands, both quantities measuring the spectral structure. The chromatic effects of each illuminant were quantitatively assessed by the CIE color rendering index (CRI), by a chromatic diversity index (CDI) and by the number of discernible colors estimated for a set of indoor scenes digitized by hyperspectral imaging. It was found that CRI decreases as the illuminant spectrum becomes more structured whereas larger values of CDI could only be obtained with illuminants with a small number of non-zero spectral bands, that is, with highly structured spectra. For indoor scenes, the maximum number of discernible colors was also obtained for highly structured spectra. Thus, structured spectra with low number of non-zero spectral bands seem to maximize the chromatic diversity of rendered scenarios but produce only modest CRI. These results suggest that highly structured illuminants may be best for applications where maximization of chromatic diversity is important.
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