Depth of field noise

[SonyBoy]

Is there any way to clean up noise in depth of field, other than increasing AA samples or lowering the threshold? I've also been a bit confused by the relationship between the depth of field check box in the global overrides section of the render settings, and the depth of field check box in the Vray physical camera attributes. It seems that you do not have to have the global check box ticked in order to render DOF with a physical camera, only the check box in the camera itself? This seems a bit contradictory. Presumably this also means that the global settings have no effect on DOF coming from a physical camera?

[Morbid Angel]

From what I can tell, physical camera depth of field has no correlation to render globals. Render globals are for non physical (old cameras).
About the noise, dof used to have its own sampling which was removed at some point. The only way to get the noise to clean up is raise max subdivs in dmc, but also raise shade rate substantially. Dmc sampler sampling image would result in slowest render time, but local subdivs in particular from lights / shaders will help to cleanup dof with minimizing use of dmc sampler max subdivs. So I think local subdivs multiplier should be increased and also min shading rate.

[SonyBoy]

Yeah, I thought I remembered explicit DOF quality settings from previous versions of Vray. I wonder why this was removed as it was obviously very useful.

[joconnell]

It was just adding more aa rays so it was a redundant control!

[Morbid Angel]

You really have to understand the DOF before understanding the noise it creates. Imagine rendering an image without it and getting a certain render time and noise. Its the image that the camera eye is seeing for that given frame. When you turn on DOF, you effectively multiply the ray directions across the scene substantially increasing the number of rays required to achieve clean image. This explains why you need to raise the dmc sampler max aa a lot. I'd suggest experimenting with denoiser as it can help a lot in eliminating some of that fine noise at the final stage.