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Transparent composition with screened footage?

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David Fuchs
Transparent composition with screened footage?
on Jul 27, 2012 at 5:05:08 pm

I'm currently working on a project that has footage disappear via overlaid transitions, which are your basic "set my mode to screen" effects on black (screenshot: http://i.imgur.com/34Mbg.png). For the editor, I want the comp to dip to transparent so that the transitions can overlay the footage inside of the NLE (Premiere, in this case.)

However, with your basic effects, a screened layer with nothing below it shows black, not transparent. The effect couldn't really be satisfactorily keyed, which leaves me wondering how to achieve the intended result without resorting to adding in the transition footage in the NLE and screening it there (creating more work for the editor.) I feel like I'm missing something really obvious, but I'm stumped.


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Juan Manuel
Re: Transparent composition with screened footage?
on Jul 27, 2012 at 5:27:11 pm

Unless I'm missing something from your post, if you're sending the editor that transition as a video file, you need to use a format which uses alpha channels (ie, transparency). Either a tiff sequence, prores 4444 or animation, among other options. Make sure you select million/trillions of colours + before you export. The plus sign indicates it's saving alpha channel.


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David Fuchs
Re: Transparent composition with screened footage?
on Jul 27, 2012 at 5:29:30 pm

The exported file is ProRes 444. The issue is that within After Effects, a screened layer with nothing below it apparently defaults to showing it as black; outside the areas of the footage the transparency shows through in the comp window just fine. I'm wondering how to ameliorate this, if there is an option, from within After Effects.


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Dave LaRonde
Re: Transparent composition with screened footage?
on Jul 27, 2012 at 5:54:26 pm

[David Fuchs] "The exported file is ProRes 444"

...which is the problem. ProRes 444 doesn't support an alpha channel. However, ProRes 4444 does.

When you write "export", I hope you really mean, "rendering a quicktime movie from the After Effects Render Queue". Then you'll have access to the Alpha Channel settings in the Output Module.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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David Fuchs
Re: Transparent composition with screened footage?
on Jul 27, 2012 at 6:05:07 pm

Augh, that's what I get for being careless. I meant to say 4444. This isn't a render issue, it's an After Effects behavior that's stumping me.

This will hopefully make it clearer:

http://i.imgur.com/cn6mQ.png

That top layer is set to screen. With nothing under it, it's showing up (and exporting with the alpha) as black. That's what I'm trying to address.


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Walter Soyka
Re: Transparent composition with screened footage?
on Jul 27, 2012 at 6:04:18 pm

[David Fuchs] "However, with your basic effects, a screened layer with nothing below it shows black, not transparent. The effect couldn't really be satisfactorily keyed, which leaves me wondering how to achieve the intended result without resorting to adding in the transition footage in the NLE and screening it there (creating more work for the editor.) I feel like I'm missing something really obvious, but I'm stumped."

You can use the free UnMult effect [link]. I usually also use Levels (set to Alpha only) to tweak as necessary.

This will remove the black background, but you can't plop a single layer meant to be screened in a comp with other layers meant for normal blending, export with alpha, and get a screened effect on that one layer only when the composite is applied in the NLE with normal blending. The blending math just doesn't work without the background.

If you need a screened look, you'll need to provide at least two layers (one for the screened layer, one for the normal layers) and the editor will have to correctly set the composite mode to Screen.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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David Fuchs
Re: Transparent composition with screened footage?
on Jul 27, 2012 at 6:06:05 pm

Ok I'll try that now. Thanks.


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David Fuchs
Worked, thanks!
on Jul 27, 2012 at 6:18:33 pm

That was just the ticket. Thanks for the link.


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