Apple Final Cut Express HD - Manual (Page 727)

Chapter 50 Adjusting Parameters for Keyframed Effects 727
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5 In the current timecode field of the Viewer, enter 01:00:02:00 to move the playhead.
6 Click the opacity keyframe button to create a keyframe at the new position of
the playhead.
Since it takes at least two keyframes to create a dynamic change to a parameter over
time, you’ll need to add another keyframe.
7 Move the playhead to 01:00:03;00 on the keyframe graph ruler, then create
another keyframe.
Entering the new
timecode moves the
playhead to this location.
A second keyframe is
added to the Opacity
value graph line.