Common Pixel Aspect Ratios For Assets; To Set The Pixel Aspect Ratio For Imported Footage; About Interlaced And Noninterlaced Video - Adobe AFTER EFFECTS 7.0 Manual

It is important to set the pixel aspect ratio for a footage file to its original ratio, not the ratio of the final output.
After Effects reads and writes pixel aspect ratios directly from QuickTime movies. For example, if you import a
movie captured as widescreen (16:9 DV), After Effects automatically tags it correctly.
See also
"Setting pixel aspect ratio for compositions" on page 113

Common pixel aspect ratios for assets

Asset Pixel aspect ratio
Square pixels 1.0
D1/DV NTSC 0.9
D1/DV NTSC Wide- 1.2
screen
D1/DV PAL 1.0666
D1/DV PAL Widescreen 1.422
Anamorphic 2:1 2.0
HDV 1080/DVCPRO HD 1.33
720 (After Effects), HD
Anamorphic 1080
(Adobe Premiere Pro)
DVCPRO HD 1080 (After 1.5
Effects only)

To set the pixel aspect ratio for imported footage

Select the footage in the Project panel.
1
Choose File > Interpret Footage > Main.
2
3 Choose a ratio from the Pixel Aspect Ratio menu and click OK.
If you are planning to render to the same pixel aspect ratio as your footage, you also need to set the pixel aspect ratio
for the composition.

About interlaced and noninterlaced video

Video can be either interlaced or noninterlaced.
When to use
Your footage has a 640 x 480 or 648 x 486 frame size, is
1920 x 1080 HD (not HDV or DVCPRO HD), is 1280 x 720
HD or HDV, or was exported from an application that
doesn't support nonsquare pixels. This setting can also
be appropriate for footage that was transferred from film
or for customized projects.
Your footage has a 720 x 486 or 720 x 480 frame size, and
your desired result is a 4:3 frame aspect ratio.This setting
can also be appropriate for footage that was exported
from an application that works with nonsquare pixels,
such as a 3D animation application.
Your footage has a 720 x 486 or 720 x 480 frame size, and
your desired result is a 16:9 frame aspect ratio.
Your footage has a 720 x 576 frame size, and your desired
result is a 4:3 frame aspect ratio.
Your footage has a 720 x 576 frame size, and your desired
result is a 16:9 frame aspect ratio.
Your footage was shot using an anamorphic film lens, or
was anamorphically transferred from a film frame with a
2:1 aspect ratio.
Your footage has a 1440 x 1080 or 960 x 720 frame size
and your desired result is a 16:9 frame aspect ratio.
Your footage has a 1280 x 1080 frame size and your
desired result is a 16:9 frame aspect ratio.
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