When I use my hand-held Minolta meter IV with my film camera, I usually have to set the meter at 80 ISO for 100 ISO film, which means I would need to open up 1/3 of a stop if I had set the meter according to the film ISO, so I do it in the meter. When I use it with my D70, I'm not quite sure (I don't really pay attention to the actual numbers, but I know its off a bit). First, I have to remember to change the ISO on the meter to 200, which I manage to do, then I shoot a test frame (studio/interior location conditions) and check the exposure on the LCD, as well as the histogram and adjust accordingly. As I recall, I still usally find myself opening up about a 1/3 to 1/2 stop, but since I shoot in RAW, I do have some latitude. Anyway, 2 stops is way off. You may want to get your hand-held meter checked, and/or double check your ISO settings as well. Also, make sure you are really in manual mode on the camera, and that no settings slipped. One of the things that pissed me off about the D70 (which I otherwise like) is that there is no setting to lock the f-stop and shutter speed in manual, like there is on my F100. Very handy in the studio where lights don't change, but accidently changing a dial can screw you up, so I'm back to using duct tape to keep the settings locked. You also should check your lens to make sure its stopping down as it should (if they stick, they usually stick "open" since that's where they start). Try using other lenses and see what happens.
Andy Pearlman Studio