Hello,
This is also one of my Main activity / passion with the Chronos, yes I found this is pretty challenging to have quality shootings with the amount of light that a strike can provide, same kind of challenge happen with DSLR :
either you open too much the aperture / Hi ISO, and you get maybe some details of fainter ramifications and more distant lightnings, with rain curtains on the way, or the image and strike gets totally burned and overexposed.
Closing too much can decrease the image crispness, can help on very bright lightnings with multiple strikes, but conversely can underexpose the fainter details, tiny lightning branches.
With the Chronos it will be the same, and you need to use a wise trade-off, of not closing too much (will generate noise like you described) and not opening too much either.
actually there wont be any rule of thumb, it would depend on many factors, the actual lighning brightness, depending on the strike distance, depending as well on dimming sources like clouds, rain or hail curtains ....
IMHO, what could help to relieve from noise in these low light followed by sudden high light with the Chronos, would be to choose a low analog an digital gain or keep it standard but not push it high.
the higher the gain, the higher the noise, alas, and i should say the Chronos is not yet fully optimized to cope with noise as efficiently as DSLR do
So you need to choose wisely your aperture depending on the average lightness amount you observe at a given moment,
and you must accept misses, and overburned or underexposed images are parts of the game
Hopefully, new coming firmwares will improve Chronos denoising, this is my hope,
and set apart the Chronos hardware / software actual limiting factors, getting trained is a key point to have successul captures.
good luck with your Lighnings chase !
Here in France we must wait couple months at least from now to have a chance to get some.
