Just remember DSLRs being digtal are way more sensitive to light, and in an outside setting being nothing really to bounce light off its going to light up whatever your working with like a christmas tree…
Talk to AMD IS THE BEST… look at all his night pictures they come out crystal…
A tripod a slower shutter and lowering the ISO will do wonders
and Like I said its not just hte pictures being grainys… it sthe angles you used in conjunction with the light, the background setting you used and the fact that your shadows are in all the pictures