I got an AS in photography back in the stone age. We may have 'pushed' (increased ASA during processing of film) some film as an assignment, but pretty much shot anything and everything at ASA (not ISO) 100-400 on 35mm, 6x6, and 4x5 formats throughout the 2 year course. There's not a whole lot you can't shoot at any given speed, by just adjusting your shutter and aperture. As mentioned, the higher ASA's get 'grainy', or noisy. I think you will discover that the primary reason for buying an advanced camera these days will be ease of access to the manual controls and adjustments. I have a D40 that makes wonderful photos, I got a few D80's because I primarily shoot manual, and the menu adjustments were driving me nuts. Attached are the high tech wonders that got me through college.