Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 71

AFTER EFFECTS CS3 65
User Guide
If you display nonsquare pixels on a square-pixel monitor without alteration, images and motion appear distorted;
for example, circles distort into ellipses. However, when displayed on a broadcast monitor, the images are correct.
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 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.
Note: To preview non-square pixels on a computer monitor, click the Toggle Pixel Aspect Ratio Correction button
at
the bottom of the Composition panel.
A
B C
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
If a footage item uses nonsquare pixels, After Effects displays the pixel aspect ratio next to the footage item's
thumbnail image in the Project panel. You can change the pixel aspect ratio interpretation for individual footage
items in the Interpret Footage dialog box. By ensuring that all footage items are interpreted correctly, you can
combine footage items with different pixel aspect ratios in the same composition.
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. Similarly, AVI and PSD files
contain information that explicitly indicates the pixel aspect ratio of the images.
If a footage item does not contain information that explicitly indicates the image's pixel aspect ratio, After Effects
uses the dimensions of the footage item's frame to make a guess. When you import a footage item with either the D1
resolution of 720 x 486 or the DV resolution of 720 x 480, After Effects automatically interprets that footage item as
D1/DV NTSC. When you import a footage item with the D1 or DV resolution of 720 x 576, After Effects automati-
cally interprets that footage item as D1/DV PAL. However, you can make sure that all files are interpreted correctly
by looking in the Project panel or the Interpret Footage dialog box.
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.
The composition's pixels aspect ratio setting should match that of the final output format. In most cases, you can
simply choose a composition settings preset. In contrast, set the pixel aspect ratio for each footage item to that of the
original source footage.