Seeing blur: 'Motion sharpening' without motion

Mark A. Georgeson*, Stephen T. Hammett

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

It is widely supposed that things tend to look blurred when they are moving fast. Previous work has shown that this is true for sharp edges but, paradoxically, blurred edges look sharper when they are moving than when stationary. This is 'motion sharpening'. We show that blurred edges also look up to 50% sharper when they are presented briefly (8-24 ms) than at longer durations (100-500 ms) without motion. This argues strongly against high-level models of sharpening based specifically on compensation for motion blur. It also argues against a recent, low-level, linear filter model that requires motion to produce sharpening. No linear filter model can explain our finding that sharpening was similar for sinusoidal and non-sinusoidal gratings, since linear filters can never distort sine waves. We also conclude that the idea of a 'default' assumption of sharpness is not supported by experimental evidence. A possible source of sharpening is a nonlinearity in the contrast response of early visual mechanisms to fast or transient temporal changes, perhaps based on the magnocellular (M-cell) pathway. Our finding that sharpening is not diminished at low contrast sets strong constraints on the nature of the nonlinearity.

Original languageEnglish
Pages (from-to)1429-1434
Number of pages6
JournalProceeding of the Royal Society: Series B
Volume269
Issue number1499
DOIs
Publication statusPublished - 22 Jul 2002

Keywords

  • contrast
  • edge detection
  • motion
  • nonlinearity
  • perceived blur

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