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Remove Black from video and export with transparency

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chris kelly
Remove Black from video and export with transparency
on Jul 28, 2012 at 4:58:06 am

Quick question, forgive my AE noobness.

I have a clip that has an object in the middle and a black background. i know I can remove the black background by screening it in the blending mode, but when I render the file the video has the black background again and no transparency. I tried some of the keying elements and they all work poorly, usually distorting the image I want to save. I export as a quicktime file PNG. Suggestions?


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Angelo Lorenzo
Re: Remove Black from video and export with transparency
on Jul 28, 2012 at 5:04:18 am

In the export dialog, did you select "RGB + Alpha" and "Million Colors+"? PNG should support transparency, so if it transparent in After Effects then the output should be as well.

The usual settings are "RGB" and "Million Colors" which is why I ask.

Angelo Lorenzo
Fallen Empire Digital Production Services - Los Angeles
RED transcoding, on-set DIT, and RED Epic rental services
Fallen Empire - The Blog
A blog dedicated to filmmaking, the RED workflow, and DIT tips and tricks


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chris kelly
Re: Remove Black from video and export with transparency
on Jul 28, 2012 at 5:08:23 am

Yeah I had it with the alpha channel. The only option I found was to change the black background to a bright green and use keylight, but that seems like a roundabout option.


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Darby Edelen
Re: Remove Black from video and export with transparency
on Jul 28, 2012 at 6:07:50 am

Most blending modes rely on RGB operations and have no effect on the alpha, so while Screen may work to composite in After Effects, it will never work if you need to export with alpha.

You have to create an alpha from the RGB of the subject if it doesn't already have alpha. Is this a solid object or something like smoke?

Possible ways to do this would include:

1. Using the Keying > Extract effect.

2. Tinting the footage, applying levels, using this layer as a Track Matte for the original footage. Adjust Levels to taste.

3. Unmult, which is useful for creating alpha from things like smoke (semi transparent objects). Looks like it doesn't work with CS6 yet, but it's a free plug-in available here: http://www.redgiantsoftware.com/products/all/knoll-unmult-free/compatibilit...

4. Try using Rotobrush if you have CS5 or later.

5. If it's a still image, do it in a photo editing package like Photoshop.

Darby Edelen


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Angelo Lorenzo
Re: Remove Black from video and export with transparency
on Jul 28, 2012 at 9:28:16 am

Well if it's against black, you could use the luma key effect without much fuss. It also affords you some edge control in a different way than the Extract effect.

Angelo Lorenzo
Fallen Empire Digital Production Services - Los Angeles
RED transcoding, on-set DIT, and RED Epic rental services
Fallen Empire - The Blog
A blog dedicated to filmmaking, the RED workflow, and DIT tips and tricks


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