Apple Final Cut Pro 7 - Manual (Page 97)

Besides simply choosing a magnification level, you can choose one of the following:
• Fit to Window: Increases or decreases the size of your media’s image to match any
size of the Viewer window. You can also do this by clicking the Viewer to make it
active, and then pressing Shift-Z (Zoom to Fit).
Before After
• Fit All: This is similar to the Fit to Window command, but this command takes into
account clips whose borders extend beyond the current Viewer boundaries.
Before After
97 Chapter 6 Viewer Basics