This paper is concerned with the combined influence of image motion an
d image resolution on (perceived) sharpness. We examined these effects
for both a fixation and a pursuit condition: only in the latter case
was it possible to follow the object in motion. In the fixation condit
ion we presented various resolution levels, and image velocities up to
5.3 deg/s. We found that sharpness decreases with object velocity, es
pecially for images with maximum resolution. In the pursuit condition
we used the same set of resolution levels, but the object velocities r
anged up to 35 deg/s. There we found only a small decrease with veloci
ty for maximum resolution images, whereas a considerable increase in s
harpness was found for images having a lower resolution. The effects o
bserved are discussed in terms of both their possible origins and thei
r implications for video encoding.