Outputting an Alpha (Matte)

Hi All,

I'm hoping to figure out a better way to do this than what I've been doing. I've been creating some keyable animations that I need to output as separate matte & fill so that it can be keyed later on a switcher.

What I've been doing: building the project in 4444 and outputting a master file in 4444. I then take that file and bring it into another project and put it in twice. Once normal, then a second time keyed over white with a "stencil alpha" blend mode. I then render this out in 422 and play it out.

The question is: is there a way to skip that last step? Can I tell FCPX or Compressor to render the composite and alpha as separate files?

If you have done your keyable animation in FCP X you are doing this the right way.

If you do the keyable animation in a compositing application such as Motion 5, you can export the composite ("fill") as a first export pass and the alpha channel ("matte") as a second export pass:



- Ronny

Thanks, Ronny. There is a Motion piece, but assembled in FCPX. Doesn't it seem like there should be a way to output the alpha channel of a 4444 project? Either through FCPX or Compressor? A menu like the one in Motion you posted?

It would indeed be useful to have such an option, especially as FCP X allows you to set a Checkerboard background to check your composites. Use the feedback form to submit a feature request for this.

- Ronny

Done.