Motion-deblurring in human vision

Abstract

SUMMARYUnder normal viewing conditions we are little conscious of blur in moving objects, despite the persistence of vision. Moving objects look more blurred in brief than in long exposures, suggesting an active mechanism for suppressing motion blur. To see whether blur suppression would improve visual discrimination of objects, we measured blur discrimination thresholds for moving Gaussian-blurred edges and bars. The observer's task was to decide which of two moving stimuli, presented successively, was the more blurred. It is known that for stationary objects the just-noticeable difference in blur increases with baseline blur ; therefore, if motion increases blur, it would be expected to increase the just-noticeable difference in blur. An active deblurring mechanism, on the other hand, would be expected to counteract the detrimental effects of motion blur on discrimination performance. We found, however, that motion increased thresholds for blur discrimination, both for brief (40 ms) and for longer (150 ms) exposures. We conclude that motion deblurring is a subjective effect, which does not enhance visual discrimination performance. Moving objects appear sharp, not because of some special mechanism that removes blur, but because the visual system is unable to perform the discrimination necessary to decide whether the moving object is really sharp or not.

Spatial-frequency discrimination of drifting gratings

“…Thus. the findings of Morgan and Benton (1989) for spatialinterval discrimination of two line segments and our present observations appear to be related to the same underlying mechanisms. Stimulus velocity affects discrimination of line separation or grating spatial frequency when the critical information is contained in the medium-high spatial frequency range and has little effect when this information is stored in the low spatial frequency range.…”

“…McKee (1975, 1977) have For the vernier targets, Westheimer and shown that discrimination thresholds for the McKee (1975) restricted their observations to offset of two vertically oriented lines remains stimulus velocities of 3.5 degjsec and less. In a unaffected by image motion for a range of recent report, Morgan and Benton (1989) replivelocities between 0.5 and 3.5 deg/sec. Intercated the findings of Westheimer and McKee estingly, vernier-resolution thresholds were and expanded their observations to stimulus affected by oblique motion, when the vertical velocities up to 6 degjsec.…”

“…An increase in the spatial-frequency bandwidth of the underlying neural mechanism would lead to a decrease in the differential output of these mechanisms and, as a consequence, to an increase in the spatial-frequency discrimination threshold. This decrease in discrimination efficiency can be thought of as a form of motion blurring (Morgan & Benton, 1989), but might reflect the simple fact that rapidly moving stimuli are encoded by neural mechanisms with broader spatial-frequency bandwidths.…”

Spatial precision of population activity in primate area MT

“…As a reference, the spatial acuity of marmoset reaches 30 cycles/degree (Ordy and Samorajski 1968), suggesting that although activity in area MT is unlikely to match the maximal acuity of activity in retina and area V1, it can provide a spatial representation with behaviorally relevant acuity. Yet, our estimates of spatial precision are difficult to relate to extant measurements of behavioral acuity, which can use form and motion signals, as well as positional signals (Morgan and Benton 1989;Verdon-Roe et al 2006;Westheimer 1987), and are likely to be task dependent.…”

Effects of motion on blur discrimination

“…In principle, these mechanisms restore positional acuity by taking into account the temporal delay at which different photoreceptors have been stimulated. The second approach 7 ' 8 does not invoke a general motiondeblurring mechanism. It assumes that image motion does introduce spatial blur.…”