<p>i'd say if you have a D5100 your iso will be a sticky point - I have had a D70, then D90, then D7000 and now have two camera's - a D600 and a D3s - all are different in terms of iso - I have a 85mm f1.8, its around $400 or so and a 50mm f1.8 - if you can get close those two lenses will be great lower cost options IMHO And I agree with what Gaute said - get close, down on the field level - </p>