(The process of saving transparency information with a clip is called “saving a clip with an alpha channel;” where “alpha channel” means “transparency information.” In fact, whenever you hear the term “Alpha” or “Alpha Channel” simply substitute “Transparency,” or “Transparency Channel.” They mean the same thing.)
EXPORT A CLIP WITH TRANSPARENCY USING FCP X
In Final Cut Pro X, we created a transparent background behind this dancing heart.
[ Here’s an article that explains how we created the transparent background behind the dancing heart using Final Cut Pro X. ]
Here’s how to export it and retain the transparent background.
In FCP X, switch to the Project Library and select the project you want to export. (Remember, you always export from the Project Library, not the Timeline.)
Go to Share > Export and set the Video Codec to Apple ProRes 4444. This is the only video codec that supports alpha channels that is available in this menu. Selecting this video codec is a critical step, because if you select any other, the transparent background won’t be included in the clip.
NOTE: ProRes 4444 generates extremely large files. Only use this codec when you need to include transparency, or to send files between After Effects and FCP. In virtually all cases, ProRes 422 or ProRes 422 HQ will be perfectly fine.
Click Next, give the file a name, pick a location and click Save. Then, see the After Export, below.
EXPORT A CLIP WITH TRANSPARENCY USING FINAL CUT PRO 7
In Final Cut Pro 7, the steps are a bit trickier, but we can achieve the same thing.
Here’s a cool way to see if a clip has an alpha channel (remember, that’s just tech speak for a clip with a transparent background).
Open the clip in the Viewer or Timeline, then select Alpha+RGB from the top-right popup menu. (You could also select Alpha, but I like seeing the image along with the transparency information. Alpha displays all opaque regions as solid white, and all transparent regions as solid black.)
When Alpha+RGB is selected, that portion of the image that is opaque is displayed in red. The portion of the image that’s transparent is displayed in black. By default, all video files are 100% full screen and 100% opaque.
In this screen shot, the image on the left is fully opaque, while the image on the right has transparent sections.
Once you’ve created a clip with a transparent background in FCP 7 – using a green screen key, luma key, mattes, or just scaling a graphic or image, you need to export it.
Either open the sequence in the Timeline, or select the sequence in the Browser.
Then, choose File > Export > QuickTime movie.
Click the Setting menu and select Custom – this choice is ALL the way at the bottom of the list.
Leave the top settings alone, they will always be fine. We only need to adjust two settings.
ProRes 4444 yields higher-quality files, because it uses 10-bit color. However, Animation files will be smaller, because it only uses 8-bot color.
These are the only two codecs shipped with Final Cut Pro 7 that support alpha channels.
HOWEVER, YOU ARE NOT YET DONE!
Once you changed the compressor, you still need to turn on the alpha channel.
Click the Advanced button – this will be dark regardless of whether you select Animation or ProRes.
In the next screen, change the Depth setting from “Millions of Colors” to Millions of Colors +. This turns on exporting the alpha channel. Without enabling the Depth, no transparency will export.
Click OK to close the Advanced dialog.
Click OK to close the Sequence Preset Editor.
Click SAVE to export your file.
Whether you exported from Final Cut Pro 7, or Final Cut Pro X, once the movie is exported, you can bring it into any application and it will recognize the transparent areas of the clip and automatically superimpose your new clip over whatever is in the background.
This is a great technique for repeatedly keying logos over backgrounds with a minimum of fuss and minimum rendering.
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