I feel like I should be able to work this out but I’ve hit a bit of a wall.
I have a night scene where I want to emulate the grain and desaturated look you get in low-light conditions, BUT, I want part of the image to retain the original colour and light reflections.
I rendered out various layers to exr with gloss/trans/emit etc components, but now I’m a bit stumped as to how to composit them.
Here is my wip image:
Here is approximately what I want (just quick lasso select in paint.net of doorway and creature, rest of image adjusted to b&w):
How do I do this? I tried layering various parts with math nodes but I always seemed to end up with everything black and white, or the image entirely lightened or darkened.