Finally DJI listened to feedback and given us what we wanted: ability to switch off in camera denoising / sharpening as well as partially given us ability to engage true second native iso. Iso 500 is not selectable from the camera
settings but it can be achieved by engaging Pro mode, setting desired shutter speed, setting ISO to auto and adjusting the exposure compensation untill the auto iso will
select 500 or just above it. After that we can lock the exposure on screen or by using one of the C buttons. Still no way to turn off the dual gain conversion in natural frame rates like 24/25/30 so this will only work in 48/50/60/120 fps. Don't get me wrong. Iso 800 isn't half bad but it might be a bit high for blue hour.
This video is only a short test and a proof of concept but do let me know what you think.