Apple Final Cut Pro 5 - Manual (Page 1059)

272 Part II Project Interchange
To change the angle between one side of a Bezier curve and the other:
m Hold down the Command key as you drag a Bezier handle.
When you release the Command key, the new relative angle of the two handles is
locked to the angle you set.
To change the length and the angle of one Bezier handle independently of
the other:
m Hold down the Command and Shift keys as you drag a Bezier handle.
When you release both keys, the new relative angle and length of the two handles you
set are locked.
Creating Keyframed Motion Paths in the Canvas
You can create motion for a clip by repositioning it, and then setting keyframes to
change the clip’s Center parameter over time. By setting enough keyframes, you can
eventually create the motion path you want.
There is an easier way, however, which can produce more sophisticated results; you set
up the motion in the Canvas using a motion path (in Image+Wireframe or Wireframe
mode). Once you set the first center keyframe for a clip in its Motion tab, all subsequent
changes made to that clip at different points in time introduce additional center
keyframes. When you create two or more center keyframes, they appear in the Canvas
along a line called the motion path.
Hold down the Command key to
change the angle of a handle
independently of the other handle.
Hold down the Command and Shift
keys to change the length and angle
of a handle independently of the
other handle.