Use the Average command to simulate the motion blur of a moving object in a clip. The motion blur is created by applying an image averaging function to each frame in the source clip. For each frame, partially transparent copies of the images in the surrounding frames are superimposed on top of the image in the current frame. Since the moving object is in a different position in each successive frame, the superimposed images in one frame will also show the object in different positions, creating the blur effect.

The number of images superimposed in one frame determines the length of the blur. You can control the length as well as the transparency of the superimposed images with the Average controls, described as follows.

Average Over fieldControls the number of frames used to calculate the average (the number of images superimposed on one frame). The Average Over value affects both the length and the transparency of the blur. For example, averaging over a large number of frames increases the length of the blur and the transparency of the superimposed images.

Weighted and Uniform boxControls the transparency of the blur. For each frame processed in a weighted average, the frame closest to the current frame carries the most weight in the average calculation and is the most opaque. The frame furthest from the current frame carries the least weight and is the most transparent. In a uniform average, all frames carry equal weight and are equally transparent.

Frames boxYou can use Past frames or both Past and Future frames to calculate the average:

• With Past Frames, only the frames that precede the current frame are considered. The motion blur follows the object.
• With Past and Future frames, the frames on both sides of the current frame are considered.