Chromatic effects of metamers of D65 on art paintings

The visual impression of an artistic painting is influenced both by the colour and by the specific spectral structure of the rendering light source. The relationship between illuminant spectral structure and visual appearance assumes particular relevance with the advent of light sources with almost arbitrary spectral distribution, like modern LED based lighting. The aim of this work was to study, computationally, chromatic effects on paintings of illuminants with the same colour as D65 but different spectral profile. Hyperspectral data from twenty oil paintings were used in the analysis. A large collection of metamers of D65 was generated and the radiance reflected from each pixel of the paintings was estimated for each of the metamers. The number of discernible colours produced for each painting and illuminant was computed, and correlated with the spectral structure of the metamers. It was found that the number of colours generated varied considerably across the collection of metamers and that the metamers producing more colours were spectrally more structured, that is, less uniform. This result suggests that it may be beneficial to explore appropriate spectral tuning in practical illumination.