Viewing Natural Scenes Through Colored Filters

Abstract

Abstract: : Purpose: Analysis of hyperspectral images of natural scenes has shown that some colored filters enhance significantly the chromatic diversity of the scenes (Linhares et al., 2004, Ophthalmic Res., 36, S1, p59). The purpose of the present work was to test psychophysically to what extent observers are sensitive to this chromatic enhancement. Methods: Hyperspectral images of natural scenes in the Minho region of Portugal were acquired over 400–720 nm at 10–nm intervals and calibrated to obtain the spectral radiance at each image pixel (Foster et al., 2004, Visual Neurosci., 21, 331–336). The effect on the spectra of light reaching the eye from these scenes when viewed through various colored lenses of commercial sunglasses and through idealized colored filters was estimated computationally. The images resulting from filtering were displayed on a calibrated 17–inch, RGB color monitor with flat screen controlled by a computer raster–graphics card providing 24 bits per pixel in true–color mode. Five observers participated in the experiment to whom it was explained how the displayed images were obtained. In each trial of the experiment the observer was presented sequentially with a pair of images corresponding to the same scene seen through different colored filters. The task was to choose the preferred image from each pair. Results: Four out of the five observers tested showed in at least 80% of the trials a preference for images derived with filters producing larger chromatic diversity. Conclusions: Observers are sensitive to the chromatic diversity of natural scenes. The use of colored filters which enhance that diversity may improve observers’ color experience and increase the chromatic information available to them from natural scenes.

Keywords: color vision • color appearance/constancy • imaging/image analysis: non-clinical