Just found this topic via a search and, since it's an ongoing issue, I see no reason to start a new topic.
I am frequently in situations where I am faced with shooting long(ish) exposures (though never more than ISO 100/6 seconds) or raising the ISO on my 1Ds Mklll.
Typically, I shoot ISO 100, 1 to 2 seconds at f/11.
For reasons of sweet spot and/or depth-of-field, let's assume that the aperature cannot be changed....
Am I right in concluding based on what's been said above, that I am better off shooting, for example, 1/2 second, f/11, ISO 400, rather than 2 seconds, f/11, ISO 100, when it comes to minimising noise?