Is denoising overlayed

Hi all

Something I’ve often wondered.

If I render something in the VFB… it finishes and denoises.

I then need to fix something - so render a region

Is the rendered region re-denoised? So it is doubly denoised in that area.

I find that I end up saving the base image then rendering the region and saving that out and fixing in Photoshop.

Denoising seems to be a secondary process (line the post values) and while still in the VFB is just used once - but I’m never sure if that’s correct.

Thanks