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Neural adjustments to image blur


Blur is an intrinsic feature of retinal images that varies widely across images and observers, yet the world still typically appears 'in focus'. Here we examine the putative role of neural adaptation1 in the human perception of image focus by measuring how blur judgments depended on the state of adaptation. Exposure to unfocused images has previously been shown to influence acuity2,3 and contrast sensitivity2,4, and here we show that adaptation can also profoundly affect the actual perception of image focus.

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Figure 1: Blur adaptation.
Figure 2: Blur aftereffects between different test and adapting images.
Figure 3: Simultaneous blur contrast.

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This work was supported by National Eye Institute Grant EY10834 (USA) and Wellcome Trust Grant 056093 (UK).

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Correspondence to Michael A. Webster.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Movie.

A demonstration of blur adaptation. The movie shows a pair of physically focused images before and after adapting for 5 sec to a sharpened (s =+0.5) or blurred (s = -0.5) version of the original image. Adaptation to the sharpened image on the right causes the original to appear blurrier, while adaptation to the blurred image on the left causes the original to appear sharper. The aftereffects are best observed by fixating the center dot, and by setting the movie to cycle repeatedly. (AVI 1055 kb)

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Webster, M., Georgeson, M. & Webster, S. Neural adjustments to image blur. Nat Neurosci 5, 839–840 (2002).

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