Adobe AFTER EFFECTS 7.0 Manual page 103

4
A 4:3 frame aspect ratio (left), and a wider 16:9 frame aspect ratio (right)
Some video formats output the same frame aspect ratio but use a different pixel aspect ratio. For example, some
NTSC digitizers produce a 4:3 frame aspect ratio, with square pixels (1.0 pixel aspect ratio), and a resolution of 640
x 480. D1 NTSC produces the same 4:3 frame aspect ratio but uses nonsquare pixels (0.9 pixel aspect ratio) and a
resolution of 720 x 486. D1 pixels, which are always nonsquare, are vertically oriented in systems producing NTSC
video and horizontally oriented in systems producing PAL video.
If you display nonsquare pixels on a square-pixel monitor without alteration, images and motion appear distorted;
for example, circles distort into ovals. However, when displayed on a broadcast monitor, the images are correct.
To view nonsquare pixels on a square pixel monitor, choose View Options from the Composition panel options menu
and then select Pixel Aspect Ratio Correction. Because it slows performance, this is recommended for viewing only.
A
Square and nonsquare pixels
A. Square pixels and 4:3 frame aspect ratio B. Nonsquare pixels and 4:3 frame aspect ratio C. Nonsquare pixels displayed on a square-pixel
monitor
When you import D1 NTSC or DV source footage into After Effects, the image looks slightly wider than it does on
a D1 or DV system. (D1 PAL footage looks slightly narrower.) The opposite effect occurs when you import
anamorphic footage using D1/DV NTSC Widescreen or D1/DV PAL Widescreen. Widescreen video formats have a
frame aspect ratio of 16:9.
If a file uses nonsquare pixels, After Effects displays the pixel aspect ratio next to the file's image thumbnail in the
Project panel. You can change the pixel aspect ratio interpretation for individual files in the Interpret Footage dialog
box. By ensuring that all footage files are interpreted correctly, you can combine footage with different ratios in the
same project or composition and generate output that plays correctly.
When you import footage with either the D1 resolution of 720 x 486, or the DV resolution of 720 x 480, After Effects
automatically sets the pixel aspect ratio for that file to D1/DV NTSC. When you import footage with the D1 or DV
resolution of 720 x 576, After Effects automatically sets the pixel aspect ratio for that file to D1/DV PAL. However,
it is always a good idea to make sure that all files are interpreted correctly by looking in the Project panel or the
Interpret Footage dialog box. For information about using interpretation rules to automate the import process, see
"To specify interpretation rules" on page 71.
Note: Make sure to reset the pixel aspect ratio to Square Pixels when you import a square-pixel file that happens to have
a D1 or DV resolution—for example, a non-DV image that happens to have a resolution of 720 x 480.
16
3
B
9
C
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