This is a very simple question (I suppose) and I could not find it already answered in the forums. Can someone explain to me why the professional lenses have such limited zoom distance, like from 12-24mm range... is this just because it can then do a distorted sort of shot at 12mm for a more radical shot? I'm looking and when I see a lens like a 16-85mm lens which is still very wide but can zoom a decent amount as well, it would seem to be a better lens, but I guess it would depend on your purposes for it. My other question is really how to tell a good quality lens from a crap lense! Why are 12-24mm lenses so expensive while you can get a different lens with much more zoom range for the same price? I apologize if this has been asked many times before! Thanks for your help.