Using transparent areas and layer masks from Adobe Photoshop

Adobe Photoshop supports a transparent area and one optional layer mask (alpha channel) for each layer in a file. You can use these layer masks to specify how different areas within a layer are hidden or revealed. When you import one layer of an Adobe Photoshop file, After Effects combines the layer mask (if present) with the transparent area and imports it as a straight alpha channel.

If you import a layered Adobe Photoshop file as a merged file, After Effects merges the transparent areas and layer masks of all the layers into one alpha channel that is premultiplied with white. (See Importing layered Adobe Photoshop files.)

If a layered Adobe Photoshop file contains clipping groups, After Effects imports each clipping group as a composition nested within the main composition. After Effects automatically applies its Preserve Underlying Transparency option to each layer in the clipping-group composition, to maintain transparency settings.

When you import an Adobe Photoshop file as a composition, any vector masks in the imported layers are converted to After Effects masks. You can then modify and animate these masks within After Effects.

After Effects also supports any blending modes applied to the file. (See Preserving underlying transparency during compositing.)