I want to take some available-light photos of people around a bonfire and I'd like to keep the ISO setting as low as possible. I know I'll have to put my camera on a tripod, but I don't have a feel for the longest exposure time that I can get away with. Of course, I'm worried that people will move a little bit and my picture will be out of focus. If the people are seated and trying to be cooperative, how long can I expect them to be still after I say "Everybody, Hold it"? 1/4 second? Perhaps 1 second? Does anyone have experience doing this?