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Motion 5, ProRes4444 alpha channel problem
Hi everyone,
I’m a long time user of Motion 5 for broadcast graphics work. Over the years, I’ve often encountered issues when we’d provide ProRes4444 with alpha channel exports of “overlay” type graphics, to post production houses, for final graphics to be re-assembled onto graded footage in the online.
Often an online editor would tell me there was dark fringing or a dark tone behind the intended artwork, or a shadow effect. I always assumed this was an AVID issue, and a Blending Mode issue (with AVID struggles with I am told, but that’s another discussion) .
But recently, I did some new tests to try to determine the extent of this issue, and whether the issue is actually with Motion and it’s ProRes4444/alpha encoding.
Exporting a simple, semi-transparent white shape, with a blur effect from Motion 5 ProRes4444 with alpha, and then dropping it into After Effects (test 1) sitting on a layer above some footage, will expose this issue – there a kind of dark shadow effect, and the alpha is not working correctly.
Exporting the very same semi-transparent white shape as a .png image sequence, and dropping it into After Effects, on the same footage, it looks correct. The semi-transparent white shape, looks white with transparency – not with the strange dark shadowy effect that the ProRes4444 gives, though there is a slight dark outline.
Stranger still, importing Motion’s ProRes4444/alpha export, back into Motion, looks great – bright white, no dark outline. But this doesn’t help me, because I have to hand off these exports to post-production houses, and this is where this issue arrises again and again. Sigh.
Some images below to demonstrate what I’m talking about.
Any suggestions, or insights into what is going on with Motion’s exporting of ProRes4444/alpha, re-composites incorrectly, vs a .png image sequence with alpha, that re-composites correctly.
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8 Replies
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Hi all, so since posting this question, I’ve done further research, and further testing.
I have now come to the conclusion that it’s all about Straight vs PreMultiplied alpha channels.Having dropped a Motion 5 ProRes4444/alpha export into After Effects again, but this time investigating the “interpretation” of the alpha – sure enough, AE was interpreting the ProRes4444 from Motion as having a Straight alpha, but I have understood the Motion’s default is to export with PreMultiplied alphas.
So forcing AE to interpret as PreMultiplied, completely solves the issue – is displays correctly.
The more critical next test will be discussing AVID with editors and online editors I am in touch with, to confirm whether AVID can do the same ‘re-interpreting’ of alphas that After Effects can
AVID’s own documentation is frustratingly scarce and insufficient, and there is very little current information only – I did find one forum discussion where it was stated that since the 2018 version of AVID Media Composer, it CAN finally be told how to interpret alpha channels… but I’m not sure…
I hope this is true – stay tuned. But if anyone has more information on AVID’s ability in this regard, please let me know.
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I seem to be having a conversation with myself here ; ) but I will now add more information.
Having spoken with an online editor, he has assured me that YES AVID can, like After Effects, be told how to interpret a clips alpha channel. This is the answer to my woes, because Motion 5 (annoyingly) seems to have no way to change its default of exporting alpha channels as PreMultiplied. No way to tell it to export Straight alphas (if I am wrong, please tell me).
And because AVID’s default is to treat alphas as Straight, I now I know I can tell online editors to direct AVID to re-interpret what we provide them (when with alphas from Motion 5) as PreMultiplied rather than Straight, and things will look correct – life will be good. I hope.
I hope this conversation with myself might be helpful so others!
Signing off
Jonathan
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Welcome to the wacky words of TV broadcast (which I just retired from) and Motion! Yes, it would be nice if Motion allowed us to chose, but Apple keeps Motion very basic and don’t seem to want Motion to become as powerful as it could be. But no, not even if you Send To Compressor, even there you can’t set how the alpha channel is handled. But you found the solution. You’d think Apple would put that in the documentation somewhere, though.
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Hey Ben,
Indeed. I don’t really understand the math behind PreMultiplied vs Straight, but why there are 2 ways of doing alphas that are continually in conflict with each other in different software – that’s just silly.
And yes, while Motion seems to have mysterious omissions in it’s quite basic settings (such as being able to choose Premultipled vs Straight alphas) I do think that Motion’s outstanding animation capabilities give it the unique distinction of being the ‘best-application-that-no-one-has-heard-of’ (other than FCP editors, that kinda regard it as a novelty software).
I am a massive fan of Motion 5, and am constantly singing it’s praises, as often as I am criticising After Effects, which I think is abysmally slow at the most simple tasks, compared to Motion 5. Motion, as those who use it know, is virtually real time, and so fast to export, which AE struggles with. How do people meet deadlines using AE?! ; )
We really do use Motion 5 almost exclusively for professional broadcast and film motion graphics, for many of the top broadcasters and streaming channels, and most people would assume that work had been done in After Effects, but it’s all Motion 5. Most people truly have never heard of it. I explain to them that it’s Motion’s answer the the After Effects problem. ; )
After Effects just dominates so much, no one questions it, or asks if there are alternatives out there. Perhaps if there was a PC version, there would be more discovery of it’s brilliance.
I am on a personal mission to illuminate this broadcast graphics industry to the fact that AE is crap and Motion is actually better. I truly believe that.
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Thanks Ben. I’ll give that a good read!
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Don’t knock AE, it is vital to higher end effects work. Most people I know who do that high end stuff whiz through AE fast. Both apps have their place. You can use one, and not bash the other.
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Hey Ben
Fair enough, but we’ve done tests where we’ve build 2 projects – one in AE and one in Motion, and where AE can take 10-20 minutes to export it’s project, Motion takes 10-20 seconds.
Don’t get me wrong, AE is unavoidable, as the industry is built around it, and it’s had virtually no competition for so long. And we use it all the time, but Motion as well.
In my opinion, AE has some series memory management issue deep down. I don’t know what it is, but all of the freelance designers we work with who use AE, all find the export times strangely long for seemingly simple comps.
Just real world example of part of my frustration with AE. Slow exporting, not real time, etc.
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