Spatial frequency and visual discomfort.

Images created from noise filtered to have an approximately 1/f amplitude spectrum were altered by adding excess energy concentrated at various spatial frequencies. The effects of this manipulation on judgements of visual discomfort were studied. Visual noise with a 1/f amplitude spectrum (typical of natural images) was judged more comfortable than any image with a relative increase in contrast energy within a narrow spatial frequency band. A peak centred on 0.375-1.5cycles/degree of spatial frequency was consistently judged as more uncomfortable than a peak at a higher spatial frequency. This finding was robust to slight differences in eccentricity, and when stimuli were matched for perceived contrast across spatial frequency. These findings are consistent with the idea that deviation from the statistics of natural images could cause discomfort because the visual system is optimised to encode images with the particular statistics typical of natural scenes.