Set how an alpha channel is interpreted, Adjust the opacity of clips – Adobe Premiere Pro CS4 User Manual
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USING ADOBE PREMIERE PRO CS4
Compositing
Last updated 11/6/2011
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It’s often most efficient to import a source file already containing an alpha channel defining the areas that you want
to be transparent. Because the transparency information is stored with the file, Premiere Pro preserves and displays
the clip with its transparency in all sequences where you use the file as a clip.
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If a clip’s source file doesn’t contain an alpha channel, you must manually apply transparency to individual clip
instances where you want transparency. You can apply transparency to a video clip in a sequence by adjusting clip
opacity or by applying effects.
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Applications such as Adobe After Effects, Adobe Photoshop, and Adobe Illustrator can save clips with their original
alpha channels, or add alpha channels, when the file is saved to a format that supports an alpha channel. In these
applications, you can display a checkerboard pattern that indicates transparency so that you can distinguish
transparent areas from opaque white areas.
Set how an alpha channel is interpreted
1
Select a clip in the Project panel.
2
Choose File > Interpret Footage or right-click (Windows) or Control-click (Mac OS) and choose Interpret Footage
from the context menu.
3
In the Interpret Footage dialog box, select any of the following Alpha Channel options and click OK:
Ignore Alpha Channel
Ignores the alpha channel in the clip.
Invert Alpha Channel
Reverses the light and dark areas of the alpha channel. This swaps the transparent and opaque
areas.
If you have difficulty identifying which parts of a clip are transparent, choose Alpha from the Program view menu in
the Program Monitor. Another way to see areas of transparency is to add a bright solid color matte on a track below
the image you are keying.
Adjust the opacity of clips
By default, clips on tracks appear at full (100%) opacity except for areas marked by a clip’s mask, matte, or alpha
channel. Make an entire clip more transparent by setting an opacity value below 100%. When a clip’s opacity value is
set to less than 100%, clips on lower tracks may be visible. At 0% opacity, the clip is completely transparent. If no clips
are stacked below a partially transparent clip, the sequence’s black background becomes visible. You can set a selected
clip’s opacity in the Effect Controls panel or Timeline panel, and you can fade a clip down or up over time by animating
opacity.
Rendering order affects how opacity interacts with visual effects. The Video Effects list is rendered first, then geometric
effects such as Motion are rendered, and then alpha channel adjustments are applied. Within each effects group, effects
are rendered from the top down in the list. Because Opacity is in the Fixed Effects list, it renders after the Video Effects
list. If you want opacity to render earlier or later than certain effects, or if you want to control additional opacity
options, apply the Alpha Adjust video effect.
If you simply want to create a fade to black, consider applying a transition such as Dip To Black to the clip instead of
animating opacity keyframes manually.
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