Apple Final Cut Express 4 - Manual (Page 769)

Chapter 48 Adjusting Parameters for Keyframed Effects 769
IX
Two-Sided Bezier Handles
Keyframes that are in between other keyframes have two-sided Bezier handles. These
handles are normally locked together, so that the curve of a parameter’s keyframe graph
line has a smooth transition into and out of the keyframe, with no sudden changes.
By default, if you change one of these handles, there’s an equal change to both sides
of the handle.
The link between these two handles can be suspended, however, to create different
kinds of sudden changes in the curve. You do this by holding down the Command key
while adjusting one of the handles.
Two-sided Bezier handles
for the smoothed
keyframe between a
beginning and end
keyframe
Lengthening one of the
handles automatically
lengthens the other.
Raising the height of the
curve on one side of the
keyframe lowers it on the
other, like a seesaw.
Hold down the
Command key to change
the angle of a handle
independently of the
other handle.