Image dimensions and aspect ratio, Frame rate, Scanning method – Apple Final Cut Express 4 User Manual
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Part I
An Introduction to Final Cut Express
Image Dimensions and Aspect Ratio
The horizontal and vertical pixel dimensions of your format determine the frame size
and aspect ratio. For example, DV NTSC video is 720 pixels wide and 480 pixels tall.
HD video is either 1280 x 720 or 1920 x 1080, and is usually referred to by the vertical
dimension and the frame rate (for example 720p30 or 1080i30).
The aspect ratio of a video frame is the width with respect to the height. SD video has
an aspect ratio of 4:3, while HD video uses 16:9.
Note: You may notice that 1280/720 or 1920/1080 is equivalent to 16:9, while 720/480 is
not equivalent to 4:3. This is because SD digital video uses pixels that are rectangular,
not square. For more information, see Appendix A, “
Frame Rate
The frame rate of your video determines how quickly frames are recorded and played
back. The higher the number of frames per second (fps), the less noticeably the image
flickers on screen. There are several common frame rates in use:
 24 fps: Film, certain HD formats, and certain SD formats use this frame rate. This may
also be 23.98 fps for compatibility with NTSC video.
 25 fps: SD PAL
 29.97 fps: SD NTSC
 59.94 fps: 720p HD video frame rate. This can also be 60 fps.
For more information, see Appendix B, “
Scanning Method
Video frames are composed of individual lines, scanned from the top of the screen to
the bottom. Lines may be scanned progressively (one line at a time), or interlaced
(every other line during one scan, and then the alternate lines on a subsequent scan).
SD video uses interlaced scanning, while high definition formats may use either
interlaced or progressive scanning. For more information, see Appendix A, “