Denoiser darkening surfaces?

[davision]

I don't recall seeing this before, but the denoiser seems to be darkening certain surfaces to some extent. It varies... sometimes it's very subtle, and other times more noticeable. (Using default DN settings, with denoise elements separately).

It is not uniform across scene -- some areas get darkened while others stay exactly the same.

Is this normal?

[davision]

I have since realized that the darkened surfaces from Denoiser happen on materials that have Trace Reflections turned Off. It can be quite dramatic.

[davision]

I guess nobody else uses Turn off reflections with Denoiser... but just so no one thinks I'm crazy...

Here is a sample scene and two renderings. One is the raw RGB and the other is denosier. The "fake" reflections (because Trace reflections is off) are being obliterated by the denoiser.

This obviously explains the darkening I'm seeing in more complex scenes where the reflections aren't as obvious. Note, I don't turn off reflections on all materials (if I did the denoiser would be less important). I just turn it off on very glossy ones since it can speed up renderings with little difference in appearance (before denoiser processes it, anyway).

[davision]

No one from Chaos has acknowledged this. Does this mean denoiser simply cannot be used when there are materials in a scene that have "Turn off Reflections" checked? Or is it a addressable bug?

[svetlozar.draganov]

Thanks for the scene, it replicated the issue right away.
No doubts, it looks like 100% bug. I'll make a note about it into our system and will get back to you once I have news for you.

[davision]

Thank you Svetlozar.