iMovie '11: Overview: NTSC, PAL, and Cinema format video
NTSC, PAL, and Cinema are video format standards that refer to the number of frames per second (fps) your recorded video contains. In general, video cameras purchased in North America use the NTSC format (30 fps), and cameras purchased in Europe use the PAL format (25 fps).
Cinema format video has a frame rate of 24 fps. This is the frame rate at which traditional film cameras shoot, and many people think this unique frame rate provides the resulting footage with a special “film-like” look. Therefore, many newer digital cameras, no matter which country they’re purchased in, have a 24 fps “Cinema” mode. You can set your camera to this mode to help give your footage that film-like appearance.
In general, when you create a new project, you should select the frame rate that you used to shoot the video. While you can mix footage with different frame rates within the same project, it can lead to poor playback performance.
After you set the frame rate for a project, you can’t change it manually. However, if the first clip you add to the project has a different frame rate from the project, iMovie prompts you to adjust the project frame rate to match.
When a video clip in your Event or project has a frame rate that doesn’t match that of the project, iMovie displays a small symbol, which shows the frame rate of the video clip, in the lower left corner of the clip. This symbol indicates that you may experience poor playback performance.
You can view your project frame rate in the Project Properties window. Choose File > Project Properties. The File menu appears in a light gray bar across the top of your computer screen.