Did some testing in a very dark room. I found two important lessons. F4 Iso1000 is far better than F5.6 at ISO2000. Stopping down is of very little importance, but ISO reduction is. I also did a shorter (192 seconds) at ISO2000 f4 to see if the length of the exposure mattered, it looked about the same as the f5.6 long exposure.
Finally I see that turning off lens correction in ACR is very important, it makes the biggest change of all.
All things considered, ISO1000 at 300 seconds f4 is perhaps useable but not great. A faster lens that is sharp wide open would make a world of difference.
Finally I see that turning off lens correction in ACR is very important, it makes the biggest change of all.
All things considered, ISO1000 at 300 seconds f4 is perhaps useable but not great. A faster lens that is sharp wide open would make a world of difference.