Change frame rate – Adobe After Effects CS3 User Manual
Page 58
AFTER EFFECTS CS3
User Guide
53
A footage item with premultiplied channels (top) appears with a black halo when interpreted as Straight-Unmatted (bottom left). When the
footage item is interpreted as Premultiplied-Matted With Color and the background color is specified as black, the halo does not appear (bottom
right).
See also
“About straight and premultiplied channels” on page 253
Set the alpha channel interpretation for a footage item
1
In the Project panel, select a footage item.
2
Choose File > Interpret Footage > Main.
3
If you want to switch the opaque and transparent areas of the image, select Invert Alpha.
4
In the Alpha section, select an interpretation method:
Guess
Attempts to determine the type of channels used in the image. If After Effects cannot guess confidently, it
beeps.
Ignore
Disregards transparency information contained in alpha channel.
Straight - Unmatted
Interprets the channels as straight.
Premultiplied - Matted With Color
Interprets channels as premultiplied. Use the eyedropper or color picker to
specify the color of the background with which the channels were premultiplied.
Set the default alpha channel preferences
1
Choose Edit > Preferences > Import (Windows) or After Effects > Preferences > Import (Mac OS).
2
Choose options from the Interpret Unlabeled Alpha As menu. The options in this menu are similar to the options
in the Interpret Footage dialog box. Ask User specifies that the Interpret Footage dialog box opens each time a
footage item with an unlabeled alpha channel is imported.
Change frame rate
The composition frame rate determines the number of frames displayed per second, and how time is divided into
frames in the time ruler and time display. Composition frame rate is usually determined by the type of output that
you are targeting. 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 typically has a frame rate of 24 fps. Depending on the broadcast system, DVD video can
have the same frame rate as NTSC video or PAL video, or a frame rate of 23.976. Cartoons and video intended for
CD-ROM or the web are often 10 to 15 fps.