About noise in general

[BBB3]

Right now I'm calculating the new image with AA DMC at 1/6, colour threshold 0.005, and the Brute Force subdiv at 70, noise threshold 0,002.
It's not going to be entirely noise free but still much, much better and it looks like it will render in about 6 hours instead of 19.

Pixela: Raising the exposure or sensitivity is the same as increasing the power of the lights, as far as I understand, and will therefore result in an increased render time. Besides, I'm not sure it would help since I, like Peter, am getting noise mostly in the lighter parts of the image. Not so much in the dark areas - or at least it's not that visible there.

[lukx]

oh... so instead bumping DMC you decide to do it with BF ... got to try it

[BBB3]

Yep, the "universal" way of doing things was getting me nowhere so decided to try that approach instead, on rivoli's suggestion, and it seemed to work. Or at least it gets me 90 per cent of the way there.

[lukx]

Bertrandt are you adding any AA filter on top of it ?

[lukx]

hmm:

[pixela]

Lukx:
No reflections on that white wall material?

[PIXELBOX_SRO]

lukx:
youre still using 0.005 threshold...have you tried 0.002?

[lukx]

-no reflections on walls
-005 is clr but i tried 002 and not much changed, only bumping up dmc subdivs helping a bit ... but again we're getting close to universal settings

[BBB3]

This seems to me the same problem I had (the noise is focused on the diffuse wall and your glossies are fine, which looks more like GI noise).
Did you try lowering the DMC setting (maybe 1/12, 0,005) and bump up brute force subdivs? Or maybe even the light's subdivs?

Yes, I use a blurring filter, especially when rendering high resolution.

[lukx]

Ok lowering DMC to 12 fixed wall noise but then I got huge blurry reflections noise.... so I bump up in DMC sampler - global subdivs multiplier to 128 and it didn't help at all

I can't bump light subdivs because I'm using only HDRI

[BBB3]

You could of course drop the global approach completely: keep your DMC low, Brute Force settings high, noise threshold around 0,002, and increase the reflection subdivisions of that specific material. See if that helps. I would not touch the global subdivs multiplier as it will raise all the settings in your scene, which can't be efficient. Better to target the problem area, as the issue of noise on the wall have shown.
For the light, you could put the hdri in a dome light (with medium-high subdivs) instead of the environment slot, or alternatively put some light portals in front of your windows.

[lukx]

this is totally mind boggling:
one wall si okay with 1/12 :

other one is HORRIBLE (blurry reflections and wall noise):

[lukx]

You could of course drop the global approach completely: keep your DMC low, Brute Force settings high, noise threshold around 0,002, and increase the reflection subdivisions of that specific material. See if that helps. I would not touch the global subdivs multiplier as it will raise all the settings in your scene, which can't be efficient. Better to target the problem area, as the issue of noise on the wall have shown.
For the light, you could put the hdri in a dome light (with medium-high subdivs) instead of the environment slot, or alternatively put some light portals in front of your windows.

Yes I'm using HDRI in dome light. I will try with portals in windows

[lukx]

I bumped glossy subdivs to 256 !! for material and no change ! Unbelievable

[PIXELBOX_SRO]

i ve been through this once with BF/LC....dropped the idea of using it because i could not understand the way it was working just because what you just described Lukx.
been usinf IM/LC ever since although i would love to use BF/LC