You can preview your movie at full screen.
Performance Considerations
The full screen preview is intended for preview only and is not recommended as a presentation tool. The speed of the preview is dependent on many factors including the speed of your computer, amount of memory, amount of video memory, size of your photos, and complexity of transitions and motion (see Improving playback performance).
To use the full screen preview, start the full screen preview by choosing → .
The full screen preview starts at the current location of the scrubber in the timeline.
Press Spacebar to pause the movie and Escape to end it.
See Improving playback performance for tips on making the full screen preview work better.