Taken from this post https://filmora.wondershare.com/davinci-resolve/how-to-denoise-in-davinci-resolve.html
Part 1: How to Reduce Noise in DaVinci Resolve Studio [paid version]:
Section 1: Denoise with Noise Reduction Feature
This advanced facility of DaVinci Resolve Studio is really useful for professional video editors. It assists in efficient cleaning of footage that is affected by external noise. This feature can be controlled easily with two different parameters:
1. Temporal Noise Reduction:
It is considered as least destructive noise reduction technique but it is observed to have some effect over performance of your computer as it may get slowed down. The best suggestion to avoid troubles during this process is to use Noise Reduction like final node and use it at end of grade.
2.Spatial Noise Reduction:
Once you have managed things with Temporal Noise Reduction parameter then there are just a few basic settings to be done in spatial Noise reduction part. You have to separate the Chroma and Luma controls by simply hitting the link symbol and make some adjustments for Chroma value increment.
Section 2: How to use Noise Reduction Feature to reduce :
Step 1: First of all, simply open the Motion effects plate on your screen. The noise reduction option can be controlled with the help of two parameters: temporal NR and spatial NR.
Step 2: Now you have to enhance the viewer mode, it will assist users to create new mode.
Step 3: Zoom in for checking deep details.
Step 4: It is time to start noise reduction with temporal noise reduction option as it is least destructive. First of all select two frames for comparison, select your desired motion estimation type; make selection for motion range and then adjust the temporal threshold settings as per need. Command D will help you to check de-noise effect.
Step 5: Now you have to move back to Spatial NR: it can be used even on motion objects. Once you have finished the adjustments with Temporal NR then you have to make minimal efforts to adjust Spatial NR.
Step 6: Simply change the mode and radius settings if needed. Make adjustments for chroma values, luma and blend mode from Special threshold panel.