Keying elements that are shot over black

Hey all! I’d love to hear tips for building an alpha channel of an element shot over black: colorful puffs of smoke. The best solution I’m getting is by doing a histogram, dividing that by the element to then comp over the plate. But of course the edges are screwy and the center of the smoke I feel would be opaque is transparent. Thanks!

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I found another way is to use the color correct node to rewire each of the channels. Make one for each; red, green, blue, and mono. Screen to combine, then plug that into the divide (instead of a histo) and comp it over.

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If its over black just make it a high contrast image? Check out channel hacks/rewires/mono to see which provides the best separation, and then use that as a matte and fill with a solid color of your choosing?

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Is that different than my rewire solution?

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Converting it to log might help.

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It thought it was…but, it could be that I just can’t be bothered to figure out what direction those little arrow go in the color corrector rewire thingy.

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Haha my solution worked. I found my own answer! :scream:

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I’m thinking it’s time to have someone back on Logik Live! :clap:t2::clap:t2::clap:t2:

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This sounds cool. I wanna try it out!

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@digitalbanshee This is such a sweet technique.

Love it

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Hi Renee,

Could you do a screen recording of his technique and share it on the forum? I’d love to see it!

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Sure!

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Out of curiosity, is rewiring the color correct different than just using a separate or mono node to isolate the channels? Like, could you just use a separate node, plus a mono node set to luminance, and screen all those channels together and get the same result? I never use the channel rewiring in the CC node so I’m not sure if there’s something unique to that process

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Inquiring minds want to know! :slight_smile:

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Separate + mono node does the same thing - yup, a simpler way to handle it.

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Thank you!!!

Another brilliant technique! Thanks

work in linear and set black to 0 then just comp it over using add .