Chapter 47, page 723 of the FCE manual
Creating Motion Effects in the Viewer
Every video, graphics, and generator clip in Final Cut Express has a set of corresponding motion attributes, each of which contains one or more adjustable parameters. When you change these parameters, you create a motion effect. By adjusting a clips motion settings, you can change its geometry to move, shrink, enlarge, rotate, and distort the clip in nearly any way you like, relative to your overall project. You can also adjust motion settings graphically, by manipulating them directly in the Canvas.
Using keyframes, you can dynamically adjust motion effects over time. You can keyframe each clips motion parameters to animate clips in your sequence, making them move across the screen, rotate, and grow or shrink over time. You can also change a clips opacity to make it fade in and out and dynamically adjust any applied filter effectsfor example, to make a clip go from a blur to sharp focus as a sequence plays. For details on keyframing, see Animating Motion Effects Using Keyframes on page 751.
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