Originally posted by OldChE Thanks for your comment. You may be right, I've not tried to compare low vs high ISO with each getting enough exposure. I'm not going to try that though, I'm not sure if it would be worth my time. I can't see spending the time to allow enough exposure at ISO 100 in such a low light situation, even if it gives an improvement in image quality. It took 10 seconds to get a good exposure at ISO 25,600, and I'm not going to wait around many times longer at lower ISO.
The point I was trying to make was that I get pretty good results at the high ISO settings, much better than I expected. I've taken other shots handheld at ISO 10,000 or so that were perfectly usable. For an old film guy (who still uses film very often) this is quite amazing and pleasing to know it can be done in a practical way.
Richard.
I meant you take the shot at the same exposure time but at the lower iso!** (If you could increase the exposure time, that is always better than higher iso.) The reasoning is when you have a minimum shutter speed to use, and maximum aperture, and the exposure is not sufficient, you have two choices: up the iso, or take the shot at a low iso and increase exposure in pp. (But this only works if using RAW.)
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** You already have the lower iso shot--you showed it. If it is a RAW capture, Just up the exposure in pp and then compare them.
I have this issue in my theatre photography all the time. E.g., I want 1/60 sec to stop motion blur, and want f/4 to get adequate DOF. And this exposure is fine for iso 1600. If instead I use iso 400 I need to increase the exposure 2 stops in pp. Comparing using iso 1600 and iso 400, the result w/ K-5 is the shadows and midtones are the same, but the iso 1600 may have blown the highlights, but w/. the iso 400 the highlights are fine.
Again since your camera does noise reduction automatically at higher iso, the comparison will favour the higher iso, but you can do noise reduction to the lower iso for the comparison--but then it depends on how you do the noise reduction. In any event noise reduction has a penalty of reduced resolution.