5

Limiting the Effect of Stencil and Silhouette Blend Modes
When you use the Stencil or Silhouette blend modes in a group set to the Pass Through
blend mode, the resulting effect carries down through every layer in every group that
lies underneath it in the Layers list, unless the group that contains it is rasterized. This
is a powerful, but not always desired effect, because it prevents you from placing a
background group to fill the transparent area.
You can limit the Stencil or Silhouette blend mode to affect only those layers in the
same enclosing group by setting the group’s blend mode to anything other than Pass
Through.
For example, if you set the enclosing group of the two layers in the Silhouette Alpha
example to Normal, then add a group underneath containing additional layers, those
layers show through the transparent areas created by the silhouetted group.
Stencil Alpha
The Stencil Alpha blend mode uses the alpha channel of the affected layer to crop out
all non-overlapping parts of layers and groups underneath it in the Layers list.
Object used for stencil End resultObject underneath
Stencil Luma
The Stencil Luma blend mode does the same thing as the Stencil Alpha blend mode, but
uses the affected layer’s luma value to define transparency. Stencil Luma is useful if the
layer you want to use for cropping has no alpha channel of its own.
309Chapter 7 Basic Compositing