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Export Alpha ONLY, FCP 7

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Espen Dale Andersen
Export Alpha ONLY, FCP 7
on May 22, 2012 at 5:53:03 pm

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.


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Rafael Amador
Re: Export Alpha ONLY, FCP 7
on May 23, 2012 at 3:33:03 am

[Espen Dale Andersen] "OK, so I have a ProRes4444 QT clip with a luma key (alpha)"
That sounds confusing and contradictory.
Luma and Alpha are two different ways to get transparency on a picture.
Can you post a still of your Prores 444 file?


[Espen Dale Andersen] "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."

Proress 422 do not support Alpha channel.
You can export a B&W matte to be used lately as a "Luma matte".
rafael

http://www.nagavideo.com


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Espen Dale Andersen
Re: Export Alpha ONLY, FCP 7
on May 23, 2012 at 10:38:36 am

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.


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Rafael Amador
Re: Export Alpha ONLY, FCP 7
on May 23, 2012 at 11:06:59 am

Put a black in V1, the picture with the Alpha in V2 and a white in V3.
Set the Composite mode of V3 (white) to Travel Matte Alpha.
You will get a gray scale movie that you can use as "Travel matte Luma" to pull the key on other picture.
rafael

http://www.nagavideo.com


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Espen Dale Andersen
Re: Export Alpha ONLY, FCP 7
on May 23, 2012 at 11:10:34 am

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.


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