Apple Final Cut Pro 7 - Manual (Page 1241)

13 Finally, you’re ready to insert the background image. Make sure that the clip you’re editing
into your sequence to use as the background image appears in a video track below the
foreground clip being keyed.
The background image
now appears.
The background image
is placed below the
foreground clip that
was keyed.
14 To really make the foreground and background look as if they were shot together, it may
be necessary to perform additional compositing steps such as blurring the background
to make it look out of focus, color correcting the foreground subject to have the same
color temperature as the background, or using motion effects to move the foreground
subject. Even with a successful key, these are the details that make a composite look like
a finished shot.
1241 Chapter 72 Keying, Mattes, and Masks