Black is not black anymore?

[AnonN10]

There is a black patch of screen that clipped through a solid sphere, where no light goes in, therefore it should be pitch black. The tonemapper seems to skew the blacks towards dark-gray, losing effective LDR range a bit and removing contrast from the image. After inspecting LUT in renderdoc, I've noticed that the pixel at (0, 0, 0) is not actually black, but has a value 0.00014.

LUT:

With tonemapper:

Without tonemapper:

[h3r2tic]

Ah, quantization, what hast thou done?

Yeah, it would probably be a good idea to special-case that. Thanks for noticing and finding the cause!

[Froyok]

I wonder if this could be related to the same issue I noticed a while ago and mentioned on Mastodon: https://mastodon.gamedev.place/@froyok/109921004547221001