Apple Final Cut Express HD - Manual (Page 796)

796 Part IX Effects
Using Video and Graphics Clips With Alpha Channels
Ordinary video clips have three channels of information for red, green, and blue. An
alpha channel contains additional information that defines areas of transparency in the
clip or image. If you import a QuickTime movie or a still image from another
application, or one that’s been created by a 3D animation program, it may have an
alpha channel in addition to its color channels. An alpha channel is a grayscale channel
where levels of white and black determine varying degrees of transparency applied to
the color channels during compositing.
When you import a QuickTime movie or an image file, its alpha channel is recognized
immediately. When you edit the movie or image file into a sequence,
Final Cut Express HD uses the alpha channel to composite it against any clips
appearing in video tracks underneath it.
Note: Alpha channels work the same in video and still graphics media files.
Don’t Add or Delete Layers From an Imported Photoshop File
Final Cut Express HD keeps track of each imported Photoshop layer according to its
position relative to the bottom layer. While editing a layered Photoshop file that’s
already been imported into Final Cut Express HD, it’s not a good idea, under any
circumstances, to:
 Add additional layers
If you add a layer, any layer pushed above the topmost layer that was imported
into your Final Cut Express HD project is ignored when you go back to
Final Cut Express HD.
 Delete layers
Deleting previously imported layers can have even more unexpected results. If you
must add or remove a layer from a previously imported Photoshop file, do this in
Photoshop, and then reimport the file into Final Cut Express HD. For additional
information about importing layered Photoshop files, see “
Importing Media Files
Into Your Project ” on page 199.