Davenn wrote in post #17965635
a little extreme in your comments, me thinks
he has some interesting info, but nothing that would make me change my ways of doing things !
his ISO info is already broadly known by anyone who has been imaging the sky for more than a year or so
I also noted his ISO tests were on cameras known for their poor ISO performance .... So I take what he said with a grain of salt,
when comparing to some of the newer cameras and their better sensors
Not sure how my comment was extreme, just my thought process when it comes to how I've evolved over the last several years in astrophotography.
His ISO tests were done on cameras he had available to him at the time he did them, which was several years ago. There are newer cameras and better sensors, but the physics and application of ISO has not changed. ISO is still a POST-SENSOR modification of signal, it is purely digital and has nothing to do with sensor sensitivity. The same thing happens now as it did 5+ years ago when you raise your ISO beyond the "ISOless" point of any digital camera (and most DSLR's these days are ISOless at some point, usually around 800-1600 ISO), you clip the highlights and significantly reduce dynamic range. In the case of astrophotography the highlights are stars, when you clip them they become white and you lose color information. Most stars in the sky are not white (or even blue, but the white balance argument is a whole other ball of wax), the vast majority, as measured by the ESA/NASA Tycho 2 star catalog, are yellow/orange/red. You are literally degrading image quality by shooting at a high ISO and because most cameras are now ISOless there is absolutely zero reason to do so. Shooting at the point your sensor becomes ISOless is the way to preserve maximum amount of data and image quality, this misconception of having to shoot at ridiculous ISO's of 3200, 6400, 24k+, needs to stop. There are lots of articles now talking about this across the internet, you probably won't bother taking the time to search them out and read, but I urge anyone just getting into this hobby (reading this thread) to google "ISOless DSLR" and learn a very important concept that affects your astrophotography image quality.
And Roger knows plenty when it comes to the ISO arguments, even with new cameras, he helped compile and collate this website (which everyone should be using when deciding on what camera to use for astro imaging):