Rendering the individual parts of the image

How can I render the individual part of the image and then paste in on the original full rendered image ?

Because when I render an image at 3000 samples some parts like smoke and lighting are still noisy, so I should render them at 10000 samples but I don’t want to render the whole image at 10000 samples because it would take too long.

So I just render one part of the image at much more samples and then copy&paste them through paint on the original image lol.

You guys know any better way, a way to do it in blender?

You should try the crop tool under the dimensions tab. This will render what ever you select. You select by pressing Shift and B then border should be checked of. Next check crop and render. You can just photoshop it over the original render. Hope this helped.

Ahh okay, i’ve already done this without photoshop but with paint. I only wanted to know is there any way of doing that in blender and not in photoshop or paint.

Have you tried using branched path tracing? Under Render Properties->Sampling choose branched path tracing and turn up the sampling for transmission and volume(I’m not sure which you need) But that allows more samples to be dedicated to the elements that need them.

You can create a second linked scene, add the border render to the second scene and then just Alpha-Over the images in the compositor, make sure crop is unticked.

Edit: You have to render the second border rendered scene first, it’s probably not worth the effort compared to just using paint/photoshop