My favorite lens is my Canon 50mm f1.2. When people talk about lenses they always talk about two things-- the focal length and the aperture. The focal length (50mm) determines the angle of view or the magnification of the subject. A 50mm lens sits right in the middle of the range-- not much magnification and not a particularly wide field of view. The second part of the lens description is the aperture-- in this case f/1.2. The aperture controls the amount of light let in the lens. The smaller the number the more light the lens lets in. Larger apertures also create a smooth blurry background behind the subject in focus. That is actually my favorite part about this lens. It's very flattering for portraits. When you put this lens on a 5dII like the one I use for all my weddings you can shoot all the way through the reception without turning on the flash. It's a great lens for shooting in a church where flash photography is off limits.