Some camcorders record high-definition (HD) video. When you import HD-format video into iMovie, you can import it in its full size or a “large” size.
If you have a MacBook, MacBook Air, MacBook Pro, or Mac mini computer, you might find that the large-size video plays back more smoothly in iMovie.
Although large-size video doesn’t preserve the quality of the full-size video, the loss in quality is typically unnoticeable when used as listed below.
Dimensions: 1920 by 1080 pixels
Space requirement: 40 GB per hour of video
Use for: exporting to Final Cut Pro, broadcasting on TV
Dimensions: 960 by 540 pixels
Space requirement: 13 GB per hour of video
Use for: viewing on your computer, publishing on the web, watching on HDTV
If you don’t know if your camcorder records video in HD format, check the documentation that came with it. Some camcorders are labeled as recording HD-format video but don’t actually record at 1920 by 1080 pixels. In this case, there’s little advantage to importing your movie in full size.
To change the size preference for importing HD-format video:
Choose iMovie > Preferences, and then click Video.
The iMovie menu appears in a light gray bar across the top of your computer screen.
Choose an option from the “Import HD video as” pop-up menu.