Visual Discomfort and Blur

Natural images typically have an approximately 1/f amplitude spectrum. Images that have relatively high amplitude at low spatial frequencies in comparison with a 1/f spectrum have been found to be uncomfortable (Fernandez and Wilkins, 2008, Juricevic et al, 2010). Such images also tend to be perceived as more blurred (Webster et al, 2002, Murray and Bex, 2010). This suggests that the loss of high spatial frequency information might increase visual discomfort. This could be due to an effect on the accommodation response, which is influenced by the spatial frequency content of images (eg, Charman and Tucker, 1977). Stimuli with a relative increase in low spatial frequency information might be uncomfortable because they are a poor stimulus for accommodation. The current study investigates the relationship between perceived blur, visual discomfort, and relative amounts of high and low spatial frequency information using both simple “bull's eye target” stimuli and natural images. Loss of high spatial frequency information was found to increase both visual discomfort judgements and perceived blur in simple stimuli. Increasing blur (loss of high spatial frequency information through either sinc or Gaussian filtering) in natural images was also found to increase visual discomfort judgements. Loss of high spatial frequency information increases discomfort, and perceived blur, in both simple and complex images. These results suggest that discomfort arises in images that present a difficult stimulus for accommodation. It is important therefore to consider how stimuli are accommodated by the eye, as well how they are encoded by the visual cortex, in understanding visual discomfort.