Adobe AFTER EFFECTS 5.5 Help Manual page 168

Adobe After Effects Help
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Luminescent Premul Prevents clipping of color values that exceed the alpha channel
value after compositing by adding them to the composition. Useful for compositing
rendered lens or light effects (such as lens flare) from footage with premultiplied alpha
channels. May also improve results when compositing footage from other manufacturers'
matting software. When applying this mode, you may get the best results by changing
After Effects' interpretation of the premultiplied-alpha source footage to straight alpha
(see "Interpreting alpha channels as straight or premultiplied" on page 31).
To apply a layer mode:
1 If the Mode menu is not visible in the Timeline window, click the Switches/Mode button
at the bottom of the Timeline window.
2 From the layer's Mode pop-up menu, choose a mode.
Using stencil and silhouette layer modes
The stencil and silhouette layer modes use either a layer's alpha channel or its luminance
(luma) values to affect the alpha channel of all layers beneath the layer. This differs from
the track matte, which affects only one layer.
Stencil mode Cuts through all layers, so you can show multiple layers through the frame
of the stencil layer's alpha channel.
Silhouette mode Blocks out all layers below it, so you can cut a hole through several
layers at once.
Note: The stencil and silhouette layer modes affect all layers below the layer to which they
are applied. To keep the silhouette and stencil layer modes from cutting through or
blocking all layers underneath, nest the layer in a composition. For more information on
nesting, see "Creating animations by nesting compositions" on page 267.
With Stencil Luma, the lighter pixels of the layer are more opaque than the darker pixels.
With Silhouette Luma, the lighter pixels of the layer are more transparent than the darker
pixels.
Stencil (left) shows all layers below through the frame of the stencil layer's alpha
channel. Silhouette (right) cuts a hole through all layers below.
To use the stencil or silhouette modes on a layer:
1 Choose Transfer Controls from the pop-up menu at the bottom of the Timeline window.
2 From the Mode pop-up menu for the layer you want to use as a stencil or silhouette,
choose one of the following:
Stencil Alpha creates a stencil using the layer's alpha channel.
•
Stencil Luma creates a stencil using the layer's luma values.
•
Silhouette Alpha creates a silhouette using the layer's alpha channel.
•
Silhouette Luma creates a silhouette using the layer's luma values.
•
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