Hey Lawrence did you ever get to the bottom of this? I had the same issue…240fps / S16 crop / 800 iso…tonne of noise and sensor lines
I understand using s16 crop will magnify any noise / sensor lines but not as much as i saw on the image…Not complaining, the other footage blows me away, will post some soon..
Having looked into it more i think it may be a more generic case of just letting more light in so when the shadows are being dropped, rather than lifted in post, that doesnt boost noise…and changing the ISO highlight settings to not burn out the highlights..
Anyhow ho[e you got it sorted!