Motion smear.

It is well known that the visual system summates signals over time, about 120 ms in daylight. Although this summation has the obvious advantage of enhancing visual sensitivity, it creates the potential problem of motion smear when viewing moving targets, whose images are also summated over time. Here I report some measurements which reveal that provided the moving target is exposed for long enough to elicit a clear sensation of motion, the amount of smear is far less than may be expected. This suggests that the visual mechanisms which signal motion are also responsible for signalling a clear unsmeared perception of the target in motion.