Apple Final Cut Pro 6 - Manual (Page 1199)

414 Part II Effects
To change the alpha channel type of a clip in the Browser:
m Control-click in the Alpha column in the Browser, then choose a new alpha channel
type from the shortcut menu.
To reverse a clip’s alpha channel:
m Do one of the following:
 Select a clip in the Timeline or open a clip in the Viewer, then choose Modify >
Reverse Alpha.
 In the Browser, Control-click in the Reverse Alpha column next to the clip you want
to modify, then choose Yes from the shortcut menu.
If there is a checkmark by the Reverse Alpha menu item, the clip’s alpha channel is
being reversed. If there is no checkmark, the alpha channel is left alone.
Exchanging Media with Alpha Channels
Alpha channels are simply grayscale images or frames, where levels of white and
black determine varying degrees of transparency. If you look at a clip with an alpha
channel in the Viewer with the Alpha option selected in the View pop-up menu, you’ll
see that the solid areas of the image are represented by 100 percent white and that
transparent areas of the image are represented by 100 percent black. Lighter to
darker shades of gray indicate lesser to greater areas of transparency.
Other editing applications may use white and black differently than Final Cut Pro. If
you’re exchanging media with other editors and broadcast graphic designers, let them
know how you need clips with alpha channels to be set up for use in Final Cut Pro.
Dark areas are
transparent.
White areas are solid.