The colour of the best illumination for appreciation of art paintings is bluish-white

The visual effects of light sources on art paintings are important aspects that should be considered by museum curators. The aim of this work was to determine the correlated colour temperature (CCT) of daylight illumination preferred by observers when appreciating art paintings. Hyper- spectral images of eleven oil paintings were collected at the museum and the appearance of the paintings under D-illuminants with CCT from 25 000 K to 3600 K was computed. In a psycho- physical experiment using precise CRT reproductions of the paintings, observers had to adjust the colour temperature of the illuminant such that it produced the best visual impression. Two groups of observers were tested: forty university students and forty museum visitors; the students were tested in the laboratory and the others in the museum. The average CCT selected in museum environment was 6755 K and in the laboratory was 6173 K suggesting that observers prefer a much more bluish-white light than that normally used in museums.Fundação para a Ciência e Tecnologia and Multiopticas Unipessoal Lda.