Using Motion Blur

Ordinarily, an animated layer appears sharp and distinct as it moves through the frame of a composition (Figure 14.5). This can appear unnatural, however, because you're accustomed to seeing objects blur as they move. In the time it takes to perceive the object at a single position (or, in the case of a camera, to record it to a frame), that object has occupied a continuous range of positions, causing it to appear blurred.