Yea, you are shooting at way too low ISO. Don't worry about upping your ISO - it's a new era in digital imaging - up the ISO so you can up your shutter speed. In a dance action shot, you should be using shutter speed of 1/200 or higher. If you shoot at ISO 200, your shutter speed will have to be way too low and your aperture too wide and you'll still end up with slightly underexposed images which will be GRAINY when you recover the shadow and blacks in post production With the D7100 you can shoot up to ISO 3200 without worrying about grains if you are shooting raw - serious. When you get to ISO 6400 or higher, you have to over expose at bit but other than that, shoot to 128,000 and be happy. BTW, the Nikon D4S as well as the Sony a7s shoot up to ISO 409,600 and looks good SOOC! Really, get use to not worrying about upping the ISO to get the exposure you want.