Use alpha channels in Final Cut Pro for Mac

Alpha channels provide an easy way to composite one image over another. You can create still images and video clips that have alpha channels using an app such as Motion, an Apple app designed to work with Final Cut Pro. Alpha channels can be thought of as having a built-in keyer—when you use the key effects, you’re creating a mask that’s used in the same way that a clip with an alpha channel is used for compositing.

Below is an example of a clip with an alpha channel, showing the image that fills the alpha channel.

The viewer showing an alpha channel fill image (a row of icons)

Below is the alpha channel image—the white areas define the video areas that are composited over the background. Any gray areas would define parts of the image that are partially transparent.

The viewer showing the alpha channel matte image

This is what the final composite looks like over a background clip.

The viewer showing an alpha channel clip composited over a background clip, superimposing a row of icons on the video background

Use a clip with an alpha channel

Position the playhead in the Final Cut Pro timeline where you want to add the alpha channel clip.
Select the clip with the alpha channel in the browser, then choose Edit > Connect to Primary Storyline (or press Q).
To see the composited clips, position the playhead within the clip that was just added above the primary storyline.

The clip is composited over the primary storyline video clip, with the alpha channel controlling the opacity of its clip.

You can also use the Opacity adjustment’s fade handles to dissolve the foreground clip on and off. See Change a clip’s opacity in Final Cut Pro for Mac.

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Final Cut Pro User Guide for Mac

Use alpha channels in Final Cut Pro for Mac

Use a clip with an alpha channel