I have been amazed how I've been able to shoot portraits or even some candids with Sigma DP2 Merrill in quite scarce indoor lighting. All shots below are taken with 1/20 s shutter speed which I find kind of a limit for my hands. I usually have to use ISO 400 to achieve that with aperture 2.8. Today I was able to use ISO 200 when I had artificial lighting from the ceiling and Tiitus was facing towards a window. Of course there is always an option for B&W shots and then ISO may well be 800 or even 1600 (this will produce lots of noise) depending on how grainy results you can stand. Actually the grain with ISO 800 is very nice looking and suits well for B&W work. So, all in all, I am very pleased so far.