Originally posted by mee It is down to opinion of what one considers usable or not.
Yep. The only thing that matters is what each person considers usable. And usable for what purpose? For family snaps I am fine with ISO 6400 or so, with good noise reduction it is an acceptable photo of an event that would not otherwise be recorded. For work, or for images that are going to be printed for sale I have far higher standards. Usually about 400 ISO on the k-3, occasionally 800. And I greatly prefer ISO 100 if I can. I honestly cringe when I have to go to ISO 200, and figure if I'm shooting at 400 I'm probably just wasting my time.
But for someone else with a different purpose, better noise reduction skills, or just different standards, use what works. That's why ISO 102,000 is there
It gets a bit tiresome though when folks post those ISO 12,000 shots to 'prove' they can take good photos at that setting. A web image with massive NR applied doesn't prove anything to me. I know better, from shooting and processing almost every day. My standards are what they are,
MY standards so I really don't care what others find acceptable.