Colouring Alpha Channel Separately

[Bruno Leone Cury]

Hi everyone.

I am receiving comps from Nuke to bring them into Resolve. I'll try to explain how and what they are:

It's a car shot of a woman driving in a green screen, which has been replaced with a street in the bg.

What I want to do and I am not being able to is to apply a CST, CDL and a LUT only to the foreground, and not to the image that replaced the green screen. And then do a color grade to this alpha channel (the street) separately.

I tried bringing in only the BG as a alpha channel, but I believe I am not doing it the right way.

Any thoughts on how this process should be done? Sorry if I wasn't clear enough.

Thank you! 

[Tom Evans]

So you have two files right, one with the background and one with the foreground? And the foreground video file has alpha channels? if that's so, just bring both the files in and stack the foreground shot on top of the background in your timeline.

Or did they provide you with the final comp shot and an external matte? 

More info please.

[Bruno Leone Cury]

Hi Tom, thanks for the reply.

So, I am receiving the final comp with the foreground and background applied, and an external matte to affect only the background.

The issue is, when I bring the comp to the timeline and apply the CST, CDL and LUT from the client, everything is affected, therefore I'm working on the external matte already with some changes.

I was wondering if, with this files I have (final comp and ext. matte) I would be able to work on the background without being affected by the CST and etc.

[Bruno Mansi]

Have a look at this tutorial by Darren Mostyn, where he does a sky replacement.

Although he generates his matte using qualifiers, you should be able to adapt it for your external matte.

 

Edited May 6, 2022 by Bruno Mansi