MOTION BLUR AND MOTION SHARPENING - TEMPORAL SMEAR AND LOCAL CONTRASTNONLINEARITY

Blurred images may appear sharper when drifting than when stationary. But, paradoxically, moving sharp edges may appear more blurred. To res olve this paradox, the perceived sharpness of drifting, blurred, squar e wave gratings was compared with that of their static analogues over a range of speeds, blurs and spatial frequencies. Both motion blur and motion sharpening occurred, depending upon the physical blur of the p atterns. For large extents of blur (>10 min are) moving patterns alway s appeared sharper than their static analogues, but for small blurs (< 10 min are) moving edges appeared more blurred than stationary ones. W e present a quantitative model for the distortion of waveforms in moti on based on two factors: (i) visual temporal integration that smears m oving images, and (ii) a local contrast non-linearity that increasingl y sharpens the effective profile of edges as speed and contrast increa se. We suggest that a plausible account of the speed-dependent non-lin earity is the differential recruitment of M and P cells at different s peeds. (C) 1998 Elsevier Science Ltd. All rights reserved.