In article ,
Chris L Peterson wrote:

Actually, astronomical cameras have the equivalent of a very low ISO
setting. They hardly apply any gain at all. This is in contrast to
digital cameras which apply a high gain when the ISO setting is large.
My Canon 300D is closest in performance to my ST8 when the former is
operating at ISO 200.

I thought the whole selling-point of CCDs for astronomy was that they
produced 0.8 or so counts per input photon, and so were vastly more
sensitive than film; and that the ISO settings on digital cameras were
set so as to knock down this sensitivity to what was expected of film.
I must be missing something.

I'm not sure how full-well effects interact with ISO settings; somehow
I'd expect the level of blooming to be independent of ISO in a camera.

Tom