Change pixel aspect ratio – Adobe After Effects CS3 User Manual
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AFTER EFFECTS CS3
User Guide
55
Change frame rate for a composition
1
Choose Composition > Composition Settings.
2
Do one of the following:
•
Choose a composition settings preset from the Preset menu.
•
Set the Frame Rate value.
Note: Jeff Almasol provides a script to set the frame rate and duration of the current composition and all compositions
nested within it:
.
Change pixel aspect ratio
Pixel aspect ratio is the ratio of width to height of one pixel in an image. Frame aspect ratio is the ratio of width to
height of the frame dimensions of an image.
A 4:3 frame aspect ratio (left), and a wider 16:9 frame aspect ratio (right)
Most computer monitors use square pixels, but many video formats—including ITU-R 601 (D1) and DV—use non-
square rectangular pixels.
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 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.
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16
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