MOTION DEBLURRING IN HUMAN VISION

Under normal viewing conditions we are little conscious of blur in mov ing objects, despite the persistence of vision. Moving objects look mo re blurred in brief than in long exposures, suggesting an active mecha nism for suppressing motion blur. To see whether blur suppression woul d improve visual discrimination of objects, we measured blur discrimin ation thresholds for moving Gaussian-blurred edges and bars. The obser ver's task was to decide which of two moving stimuli, presented succes sively, was the more blurred. It is known that for stationary objects the just-noticeable difference in blur increases with baseline blur; t herefore, if motion increases blur, it would be expected to increase t he just-noticeable difference in blur. An active deblurring mechanism, on the other hand, would be expected to counteract the detrimental ef fects of motion blur on discrimination performance. We found, however, that motion increased thresholds for blur discrimination, both for br ief (40 ms) and for longer (150 ms) exposures. We conclude that motion deblurring is a subjective effect, which does not enhance visual disc rimination performance. Moving objects appear sharp, not because of so me special mechanism that removes blur, but because the visual system is unable to perform the discrimination necessary to decide whether th e moving object is really sharp or not.