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oskarmatzerath
Known Participant
October 26, 2023
Question

"Alpha Add" in Premiere to get rid of edges?

  • October 26, 2023
  • 2 replies
  • 646 views

I'm the AE guy working with an editor on Premiere, with a project which is being exported as layers with alphas so the colorist can treat screen comps separately from the rest. I'm exporting as 4444's with an alpha, but when layered in Premiere there is an ugly edge around the alpha. This is the kind of thing that "Alpha Add" in AE fixes, but I can't find something like that in Premiere. How can you get Premiere to work with layers with inverted alphas (a pretty fundamental need, I would think)? Because of the parties involved, prerendering everything colored and layered in AE isn't practical, and isn't a solution, anyway.

    2 replies

    Shebbe
    Community Expert
    ShebbeCommunity Expert
    Community Expert
    October 27, 2023

    I would personally take a different approach. Just export the desired alpha channels into RGB ProRes renders (as Alpha only instead of RGB+Alpha out of AE) and have the colorist use those as mattes to access the fore/background data. This way you don't have to manage the blending and deal with multiple RGB renders of the actual data. You just export the full composite RGB and any extra matte is black and white data only. It's a much cleaner workflow because the editor doesn't need to blend anything, only manage the single render out of comp and then the updated version that coming from grading.

      R Neil Haugen
      R Neil Haugen
      Legend
      October 27, 2023

      Shebbe is a *rather* experienced user in Resolve amidst color ... and of course, David is a total wonk on Ae.

       

      Getting both of them giving options on this thread is wondrous ...

      Everyone's mileage always varies ...
      R Neil Haugen
      R Neil Haugen
      Legend
      October 26, 2023

      That's I thnk the old multiplied/pre-multiplied thing? You can set that in Ae, but you can't ... Premiere needs ... I think, if I recall correctly ... pre-multiplied alpha.

       

      @David Arbor  @Jarle Leirpoll ... you're good with Ae/Pr workflows ... do I have that correct?

      Everyone's mileage always varies ...
      D
      David Arbor
      Inspiring
      October 27, 2023

      The documentation says that Premiere supports both straight and premultiplied alphas, so @oskarmatzerath, that would be the first thing I would try. The ProRes 4444 Output Module in AE defaults to a premultiplied alpha, so try switching it to straight. 

       

      Alternatively, you could render out ProRes 422 or HQ and then render your alpha as a separate pass so the editor can use it as a luma track matte.

        R Neil Haugen
        R Neil Haugen
        Legend
        October 27, 2023

        Thanks for popping in, David!

        Everyone's mileage always varies ...
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