i'm a freshman photography major at columbia college, i have a new canon rebel xs with a standard lense and a portrait lense. i need a 35mm camera for my darkroom class. i have already invested so much money into the DSLR, i that i would so prefer to have a camera with interchangeble lense options. i've been told that canon notoriously changes the sizes and whatnot of their lense mounts. am i going to have to get over it and just buy a whole new camera with totally different lenses? help me out!