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ProRes 4444 alpha breaks w/ cc
I rendered out a clip from AE w/ ProRes 4444. Imported into FCP and placed over another clip in the timeline and the alpha is fine. Then added a 3-way CC and adjusting that worked as expected until I enabled the limit effect, then the alpha got replaced with black. Which Channel operation might help isolate the A from the RGB so that the CC is only being applied to RGB? I’m familiar with the Shake workflow but haven’t used the Channel operations too much in FCP.
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6 Replies
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this has always been a problem with FCP’s 3 way CC. Here’s my workaround:
Place a copy of the clip with the alpha above itself. Apply the CC to the top clip. Set the composite mode on the top clip to “Track Matte Alpha”. That will use the alpha channel on the middle clip (which is a duplicate of the one above) regardless of what the 3 way CC is doing.
I’ve used this method to make “power windows” in FCP before there was an option to use the Colorista plugin.
Arnie
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Thank you Arnie.
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Hi Brad,
Did you exported from AE with Strait or Premultiplied Alpha?
rafael -
Premultiplied. I just noticed that when I drag the rendered clips into my FCP Bin, they’re coming in with the Alpha as None/Ignore, and I have to switch it to Straight before cutting into the timeline.
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[Brad Buss] “I just noticed that when I drag the rendered clips into my FCP Bin, they’re coming in with the Alpha as None/Ignore, and I have to switch it to Straight before cutting into the timeline.”
That’s pretty much standard with FCP. You almost always have to set the alpha manually with clips.
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In applications like AE, Shake and Combustion you need to “de-multiply” any Premultiplied Alpha before applying any Color Correction filter. If not the CC will affect the Alpha channel as well.
De-multiplying the CC will only affect to the YCbCr/RGB info.
On top of that you are using the effect limiter which is generating a key on top an already existing Alpha channel. May be too much for FC.
FC is much more limited than AE and similar to manage Alpha channels.
FC export only Strait Alpha and I guess may work better with that kind.
rafael
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