Applying film grain only to very dark parts of the image

[Carapettu]

I’m not that experienced with unreal and I’m trying to replicate how real cameras work, where the grain tends to be more pronounced/colored in very dark parts of the image.
The standard “Film Grain Intensity Shadows” setting on the camera is far too lenient to what it considers “shadows”. I needed this to be only added to black/almost black parts of the image.

I figured I’d need to mask the black parts manually, add my own film grain effect, and then apply that post process material to the camera.

I didn’t get very far, and I could be completely wrong here, but everything I tried after this failed miserably. I’ve been stuck on this for ages, and nothing on the internet seems to solve this (or perhaps I just didn’t know what to look for).

I’d be very grateful for any kind of help with this.

[pezzott1]

An idea that might be worth exploring could be in a post process material calculate luminance and use it as a mask:

Hope it helps.

[Carapettu]

This was very helpful! Thanks a lot. I managed to get the desired effect perfectly.