Implicit knowledge of the colours of natural scenes matches real colours

Abstract

Some studies suggest that there is a memory colour effect for familiar objects but whether this effect generalizes to natural scenes is unclear. Here we tested this hypothesis with an experiment where observers adjust the colour gamut of unknown natural scenes to produce realistic images. The stimuli were images of natural scenes unknown to the observers synthesized from hyperspectral imaging data. The images were rendered under D65 and could be manipulated to adjust the colour gamut in the CIELAB (a*, b*) by a multiplicative factor between 1.5 and 0.5. The images were presented on a calibrated CRT computer screen driven by a ViSaGe MKII. In the experiment the observers adjusted the gamut by actuating freely on a joy-pad. At the beginning of each trial each image was presented with its colour gamut compressed or expanded by a random factor. The task of the observers was to adjust the gamut such that the image appeared real. Data from five observers with normal colour vision shows that, on average, the gamut selected by observers was within 2% of the original one. These results suggest that observers have implicit unbiased knowledge of the colours of natural scenes.