Noise issue with reflection in window glass

[tinybot]

I'm using 3.50.04, with all the settings set to default (by switching to another renderer and then switching back to V-Ray).

The only changes I've made to the defaults: changed the render time to "0.0", changed the noise threshold to 0.02, added a bunch of Render Elements, including Reflection and Denoiser.

Here is the final output after some work in Photoshop:



Generally I like the results (although I would absolutely love any critique/feedback on how to improve), but as you might see, in the window glass, there's quite a bit of noise, which is coming from here:



I used the Reflection render element to make the reflections in the scene more prominent in post. Most of the Reflection render element is pretty noise-free, except for the window glass! I thought it was because I had such a high noise threshold and was relying on Denoiser to smooth things out, but I think the Denoiser only affects the final RGB output? (Although I find it strange that only the glass reflection is noisy and the rest of the reflections are fairly noise-free?)

Any suggestions on where or how to start troubleshooting?

Thanks!

[yolov]

Hi,
As the reflection channel is quite noisy, you'll need to increase sampling to clean it up a bit. You could get away with just increasing the min shading rate. In either case, the downside would be that the render time will increase.
If you're going to only tint the reflection, then comping back the channels to beauty will not be noisier than your original RGB image. But if you're going to increase the gain or the contrast for the reflection, then it will show, unfortunately.
You could avoid rerendering f you're doing the compositing in nuke, you could use our denoiser plugin for nuke and only denoise the reflection channel, do the corrections and put the image back together.
The other way would be to save out the reflection channel to a separate image and run it with the standalone denoise tool and use the threshold parameter.