Easy fix:
Setup / image setup:
Exposure mode: customize1 (or 2 or 3)
Max gain 0-12 (the lower the better)
Shutter: min 1/10000, max 1/30
Denoise: the less the better
Brightness: as needed
Longer max shutter speed allows more light in, so the best is 1/8th of a second, but I'm using 1/30th of a second in order to get 30 frames per second in video. Video still looks ok at 8 frames per second, so use longer than 1/30 for even less grain if needed. This will allow you to reduce the gain. Gain combined with faster shutter speed is what causes graininess. Photography 101.
Enjoy
