ABSTRACT
A layer’s luminance or alpha channel can be used as a stencil. This chapter covers the Preserve Transparency switch, and an obscure but useful mode called Alpha Add. A silhouette is nothing more than an inverted stencil. The options offered are Silhouette Luma and Silhouette Alpha, based again on whether the luminance or alpha of the layer dictates the transparency. When the Preserve Underlying Transparency switch is turned on for a layer, the combined transparencies for all layers underneath affect the transparency of the layer have turned it on for. This useful feature tends to get overlooked by many users. First, it shows up as a nondescript little T switch in the Modes column. Second, if one of the layers in the comp underneath the one getting preserve transparency is full-frame, this switch will have no effect, since there would be no transparency to borrow.
