I just shelled out for my first DSLR (Canon Rebel XT). Being completly tapped out at the moment I went and grabbed some 2nd-hand generic 70-210 AF lens for CAD$50 just to have some variety on practice shots. I have to shoot in manual Aperature mode as it only has f4 and the Camera doesn't pick up on that, and I'm sure the quality leaves alot to be desired. But for 50 bucks it good enough to practice on until I can afford something sensible. I guess my question is am I safe using an older 35mm based lens? Its no heavier than any other 35mm lens and it works fine with AF. Is there anything I should know before using this thing?