User Guide

105
ADOBE AFTER EFFECTS 5.0
User Guide
Setting pixel aspect ratio for compositions
Most computer monitors use square pixels, while ITU-R 601 (D1) and DV video use
rectangular pixels. The Pixel Aspect Ratio option compensates for the rectangular pixels
of D1 video format. Set the pixel aspect ratio that corresponds to your final output format.
See “Setting pixel aspect ratio” on page 88.
If you intend to create a movie for the D1 output format, choose D1 NTSC or D1
PAL. For more information about D1 format, see online Help.
Note: The correct pixel aspect ratio for D1 NTSC or D1 PAL is chosen automatically when
you choose the corresponding preset item.
Setting frame rate
The composition frame rate determines the number of frames displayed per second.
Frame rate is usually determined by the type of output you produce. NTSC video has a
frame rate of 29.97 frames per second (fps), PAL video has a frame rate of 25 fps, and
motion picture film has a frame rate of 24 fps. Video intended for CD-ROM or the World
Wide Web is often 10 to 15 fps.
Each motion-footage item in a composition can also have a frame rate, and the
relationship between the footage-item frame rate and the composition frame rate deter-
mines how smoothly the layer plays. For example, if the footage-item frame rate is 30 fps
and the composition frame rate is 30 fps, whenever the layer advances one frame, the next
composition frame is displayed. If the footage-item frame rate is 15 fps and the compo-
sition frame rate is 30 fps, then two composition frames are displayed before the current
layer advances one frame, unless frame blending is enabled. (See “Using frame blending”
on page 150.)
When you use footage that was shot or rendered at the NTSC-standard rate of 29.97 fps
and the composition frame rate is 30 fps, approximately two footage frames will be
repeated every minute to compensate for the differing rates. To avoid repeated frames,
make sure that your composition frame rate matches your source footage, or enable frame
blending for the layers.
UG.book Page 105 Wednesday, February 21, 2001 12:05 PM