Apple Final Cut Pro 5 - Manual (Page 1706)

Appendix A Video Formats 355
V
Aspect ratio can be expressed as absolute dimensions (4 x 3), a ratio (4:3), a fraction
(4/3), or as the decimal equivalent of a ratio (1.33:1 or, simply 1.33).
 Video aspect ratios are often written as ratios, such as 4:3 for standard definition
video or 16:9 for high definition video.
 Film aspect ratios are often written as decimal equivalents, such as 1.33, 1.85, and
2.40. The higher the decimal number, the wider the image. An aspect ratio of 2.40 is
wider than 1.85, and 1.85 is wider than 1.33.
 Digital video resolutions are usually written as absolute pixel dimensions, such as
720 x 480, 1280 x 720, 1920 x 1080, and so on.
Below is a list of commonly used aspect ratios, mostly from the film and television
industry, plus a few others for comparison:
Frame Dimensions, Number of Lines, and Resolution
A video frame is composed of lines. In digital video, each line is sampled to create a
number of pixels (samples) per line. The more lines per frame, the higher the image
resolution. The more pixels per line, the higher the resolution of each line.
Number of Lines
NTSC uses 525 lines, while PAL uses 625. In analog video, many lines are not actually
used for picture information, so the total numbers relevant for the picture are
somewhat smaller: 486 lines for NTSC and 576 lines for PAL. High definition formats
defined by the ATSC have either 1080 lines or 720 lines per frame.
Pixels (Samples) per Line
In digital video formats, each line is sampled a number of times. In an attempt to create
a single digital VTR that could digitize and record both NTSC or PAL signals, the
ITU-R 601 specification uses 720 samples per line for both NTSC and PAL. Therefore, a
digital NTSC video frame is 720 pixels x 486 lines, and a PAL video frame is
720 pixels x 576 lines.
High definition video with 1080 lines uses 1920 pixels per line (1920 x 1080). 720-line HD
video uses 1280 pixels (1280 x 720). Both of these formats have an aspect ratio of 16:9.
Aspect ratio Medium
1.33 (4:3) Television
1.37 Camera footage (prior to projection)
1.66 Standard European film masked in projector
1.78 (16:9) High definition television
1.85 Standard North American film projector
2.40 (used to be 2.35) Widescreen (anamorphic) film projector