See my replies in this thread - lots of info on why image sensors behave the way they do:
Why am I getting grain in shadows from my Air? Settings: ND 4 4k 30fps 1/60 shutter. D-Cinelike Standard Profile Mild sunny Am I doing something wrong with the settings? I get noticeable grain jitters in the dark spots(shadows) for some reason. Photography, I get insane amount of grain in...
mavicpilots.com
The still photo quality of the Mavic Air is unfortunately quite poor, even compared to today's smartphone standards. The biggest reason for this is a 1/2.3" sensor is just so tiny, and it lacks all the benefits of computational photography (Image stacking, instant HDRs, etc.) that you also find in today's smartphones. You can get some acceptable results though if you expose properly and are willing to process the RAW file a little bit, just keep your expectations in check.
Here is the important bit from my posts re: shadow noise or high contrast scenes:
The reason for this is how image sensors work - they achieve best image quality when they have been saturated with light to the point that they can reach their full well capacity (where the ADC reaches maximum value, which is at base ISO). If the bright/highlight areas are properly exposed, that typically means far less light has been collected by the photosites responsible for the dark areas, and as a result they are going to be full of noise. When you raise the ISO, the ADC is told to reach maximum value much earlier, hence the dynamic range reduction at higher ISO levels, because it is working with far fewer electrons before it reports a maximum value. This is also why you see grain/noise at higher ISO levels, because the ADC is reporting maximum value with only a tiny fraction of the light collected compared to base ISO FWC, and light is collected randomly (noise also occurs randomly, which is why stacking multiple high ISO images is an effective form of noise reduction).
This is not a problem unique to DJI or the sensor in the Air - no camera can expose all areas of a scene like that with such high dynamic range. There will always be more noise in the shadows, and the 1/2.3" sensor isn't giving you a ton of flexibility - it's essentially the same sensor in many modern smartphones today, minus all the computational photography goodies. Shooting high contrast scenes like that is simply not ideal because you can only expose for the shadows or the highlights - not both. Choosing the light that you fly in has one of the biggest effects on how good your footage will look, and that goes for 'standard' photography as well. Any time you have ultra high contrast and strong shadows, the result just isn't going to be good. What you usually want is for your subjects to be very evenly lit, and then you can pick a single exposure for the whole scene and everything will look great.