Apple Final Cut Express HD - Manual (Page 732)

732 Part IX Effects
For example, if you space keyframes 2 seconds apart in the Rotate setting, the resulting
rotation lasts 2 seconds. If you apply smoothing to one of the keyframes, the total
duration of the rotation remains 2 seconds, but the rate at which the clip rotates to full
speed and then slows down to a stop is different over the course of those 2 seconds. If
you move the two keyframes closer together, the rotation happens faster; if you move
the two keyframes farther apart, the rotation happens slower.
Understanding Bezier Handles and Curves
When adjusting the Bezier handles that are attached to a smoothed clip, there are
several kinds of curves you can create, which result in different velocity rates.
 The steeper the curve of the Bezier handles in the parameter’s keyframe graph line
(or overlay), the faster the rate of change.
 The shallower the curve of the parameter’s keyframe graph line (or overlay), the
slower the rate of change.
The kinds of curves you can apply to a keyframe depend on that keyframe’s location
relative to other keyframes on the parameter’s keyframe graph line.
Two keyframes with
no smoothing
Bezier handle on one
side of a smoothed
keyframe
Constant rate
of change
Shallow rate
of change
Steep rate
of change