I'm reading a "learn at home" photography book with review questions in the back and there are few that I still can not figure out please help! Sorry if any of these question are dumb its hard for me to learn on my own! -Thanks 1) To aviod perpective distortion when shooting portraits, is a 50mm lens and good choice to use for a 35mm camera? 2) Is a lens of around 50mm is regarded as a normal lens for all cameras regardless of flim size? 3) To avoid linear distortion when photography a tall buliding with a 35mm camera, should you position the camera so that the face of the lens is parallel to the face or side of the building?