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!

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.

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?

Is that different than my rewire solution?

Converting it to log might help.

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.

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

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

This sounds cool. I wanna try it out!

@digitalbanshee This is such a sweet technique.

Love it

Hi Renee,

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

Sure!

16 Likes

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

Inquiring minds want to know! :slight_smile:

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

Thank you!!!

Another brilliant technique! Thanks

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