Adobe AFTER EFFECTS 5.5 Help Manual page 166

Adobe After Effects Help
Using Help | Contents
To preserve underlying transparency:
Select the T option in the Layer Switches column for the appropriate layer.
Using layer modes
Layer modes control how each layer blends with or reacts to layers beneath it. The stencil
and silhouette layer modes affect the alpha channels of layers beneath them. Other layer
modes affect how colors appear when blended with the colors from other layers. Layer
modes in After Effects are identical to layer modes in Adobe Photoshop.
Layer modes cannot be animated using keyframes. If you want a layer mode to change at
a certain time, split the layer at that time and apply the new layer mode to the part of the
layer that continues. You can also use the Compound Arithmetic effects, which are similar
to layer modes but can change over time. For more information on splitting layers, see
"Creating new layers by splitting" on page 74. For more information on Compound Arith-
metic effects, see "Compound Arithmetic" on page 190.
When using layer modes, it is helpful to think of the effects in the following terms:
The underlying colors are the colors of the layers located below the layer to which you
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want to apply the mode.
The layer colors are the original colors in the layer where you set the layer mode.
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The resulting colors are the final colors displayed.
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Specifying a layer mode
You can apply one of the following layer modes to a layer:
Normal Composites the layer on top of underlying layers.
Dissolve Randomly replaces layer colors with colors from underlying layers, based on
layer transparency.
Dancing Dissolve Functions the same as the Dissolve option, except that the placement
of random color changes varies over time.
Add Combines the color values of the layer and underlying colors. The resulting color is
lighter than the original. This is a good way to combine nonoverlapping images in two
layers. Pure black in a layer does not change the underlying color. Pure white in the under-
lying color is never changed.
Multiply Multiplies the color values in the layers and divides the result by the maximum
pixel value of either 8-bit or 16-bit pixels, depending on which mode you are in. The
resulting color is never brighter than the original.
Screen Multiplies the inverse brightness values of the colors in all layers. The resulting
color is never darker than the original. Using the Screen option is similar to the traditional
technique of superimposing two different film negatives and printing the result.
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Working with Masks and Transparency
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