First of all, I think it would make sense to update to Corona 11, unless you are in the middle of a project -
https://corona-renderer.com/downloadInstead of using a specific noise limit, I would suggest the following workflow:
- start rendering your image in a lower resolution like 1920p or even 1280p
- after a few passes (which should not take a lot of time) you should see which areas of your image are the most "challenging" (noise or hard edges are visible)
- set your output to your final resolution
- do a region-rendering of the challenging area that you found in point 2
- observe how many passes you need to get a clean rendering (or "good enough" quality)
- then set that pass limit for the whole image and render it
One other possibility is that there is some issue in your scene. If you would like us to inspect it, feel free to contact us at
https://support.chaos.com/hc/en-us/requests/new