Hour 15. Compositing Part 2: Alpha Channels and Mattes

Another way to layer is to create holes in clips?digital holes, that is?using alpha channels and mattes. Alpha channels are common elements of graphics created in programs such as Adobe Photoshop and Illustrator. Premiere turns them transparent. Mattes appear to be simple black and white, opaque images, but again Premiere uses them to create transparencies. Both are effective, useful means to composite clips in Premiere.

The highlights of this hour include the following:

• Alpha channel transparencies?straight and premultiplied

• A dozen premiere video effects that use alpha channels

• How mattes work

• Using mattes, including image mattes, track mattes, split screens, difference mattes, and garbage mattes