Originally posted by MJKoski The purpose of the comparison was based on the idea that no filtering happens at base ISO and when boosted one can use ISO invariance capabilities to crank up the exposure and avoid any damage done by overzealous filtering.
How did you establish that the result you got from underexposing 3 stops and boosting in PP is better than just shooting at 6400 ISO? Is that a practice you use in film?
How do you know Pentax has done the same thing Sony did? Different algorithms should produce different results.
Why did you consider 800 ISO to be the equivalent of "base ISO." (Hint base ISO is 100 ISO.)
You are trying to safe-guard against over-zealous filtering based on your experience with Sony. But surely you need to show that used correctly such an effect exists with Pentax. If you ask me, I always shoot and 100 ISO where possible, because according to every curve ever published, that's where you get the best resolution, Dynamic Range and colour depth. So given that you should always use the lowest ISO in any circumstance, I'd suggest you're just stating the obvious.
In simple terms, you gotta do what you gotta do. When I go to 800 ISO it's because there are reasons why I won't get any acceptable image at 400 ISO, ditto for 400 ISO and 200 ISO, then 200 ISO and 100 ISO.
So if because you need a faster shutter speed, or more depth of field or whatever, even if an 800 ISO image isn't the best possible in terms of IQ, you still have to evaluate your trade offs and go with it. It may be better than a subject with motion blur. It amay be better than really narrow depth of field. I don't see how this changes that. And that has nothing to do with what Sony, Nikon, Canon or Pentax did. That's just photography 101. The same across all platforms, digital and film.