September 2017
Volume 17, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2017
Metameric Mismatching in Natural and Artificial Reflectances
Author Affiliations
  • Arash Akbarinia
    Centre de Visió per Computador, Universitat AutoÁnoma de Barcelona
  • Karl Gegenfurtner
    Abteilung Allgemeine Psychologie, Justus-Liebig-Universität
Journal of Vision August 2017, Vol.17, 390. doi:10.1167/17.10.390
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      Arash Akbarinia, Karl Gegenfurtner; Metameric Mismatching in Natural and Artificial Reflectances. Journal of Vision 2017;17(10):390. doi: 10.1167/17.10.390.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The human visual system and most digital cameras sample the continuous spectral power distribution through three classes of receptors. This implies that two distinct spectral reflectances can result in identical tristimulus values under one illuminant and differ under another – the problem of metamer mismatching. It is still debated how frequent this issue arises in the real world, using naturally occurring reflectance functions and common illuminants. We gathered more than ten thousand spectral reflectance samples from various sources, covering a wide range of environments (e.g., flowers, plants, Munsell chips) and evaluated their responses under a number of natural and artificial source of lights. For each pair of reflectance functions, we estimated the perceived difference using the CIE-defined distance ΔE2000 metric in Lab color space. The degree of metamer mismatching depended on the lower threshold value l when two samples would be considered to lead to equal sensor excitations (ΔE < l), and on the higher threshold value h when they would be considered different. For example, for l=h=1, we found that 43.129 comparisons out of a total of 6×107 pairs would be considered metameric (1 in 104). For l=1 and h=5, this number reduced to 705 metameric pairs (2 in 106). Extreme metamers, for instance l=1 and h=10, were rare (22 pairs or 6 in 108), as were instances where the two members of a metameric pair would be assigned to different color categories. Not unexpectedly, we observed variations among different reflectance databases and illuminant spectra with more frequency under artificial illuminants than natural ones. Overall, our numbers are not very different from those obtained earlier (Foster et al, JOSA A, 2006). However, our results also show that the degree of metamerism is typically not very strong and that category switches hardly ever occur.

Meeting abstract presented at VSS 2017

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