Export Alpha ONLY, FCP 7

OK, so I have a ProRes4444 QT clip with a luma key (alpha) imported in a FCP 7 project.

I want to isolate the alpha channel and export the clip as to two separate files, FILL and KEY, to two ProRes422-files in QT-wrappers.

How do I do this? I have spent an hour searching, but all I have found are tips on how to export files with alpha included in the file. That is not what I want.

I can view the alpha alone by going "View->Channels", but I do not know how to export it.

Any help would be much appreciated.

Regards from Norway.

Thanks for answering.

The key is an alpha channel, but I want to export it as a greyscale Luma matte, that is correct.

How do I isolate the alpha and export it alone?

Here is a frame grab of the alpha as viewed alone in FCP.



Again, thanks.

Thanks!

In the mean time I made it work by using the filter "Channel Swap" under Channels in FCP7. I swapped all the RGB-channels with the alpha channel and exported. It did, however, lead to a long render time so I suppose your way is a better one.

Thanks again. Now I can playback the fill and the key separately from my plaback server.

Espen.