Can’t render out alpha in simple video file

Jun 23

Can’t render out alpha in simple video file

I have a read node in Nuke with a .mov file which definitely has an alpha channel (an explosion).

The simple question is how do I export this from Nuke while maintaining the alpha channel?

I want to do this directly, in other words I have nothing else plugged into it, just want to render it out with alpha as a test.

It’s to then be opened in FCP, and I’m using Apple ProRes 4444 which is supposed to support alpha channels. I have tried PNG too which is the format the clip is originally in and that hasn’t been a success either. In FCP I make sure to change clip to ‘straight alpha’ in ‘item properties>format’.

^Despite this, I have no alpha channel after the render from Nuke.

I’ve tried many different settings of ‘premultiplied’/’auto alpha’ etc. and I get no joy.

I know/think it’s going to be something simple, but I just can’t see it!

If this test works, then I am hoping to key some footage with Primatte and export the footage with alpha for compositing in FCP, so this was meant to be a ‘simple’ test. Is it possible to do that – remove green screen and export the footage with alpha channel for direct overlaying in FCP?

Thanks for any help.

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Hasta La Motion!