One of the biggest discussions in selecting lenses, is usually which one to get. The choices are generally govern by your budget, your goals, need, and in some cases: want. For the most part, the choice is simple, if you shoot in low-light conditions (weddings, ceremonies, events) or need to freeze action (sports), you need fast aperture lenses for faster shutter speeds and then you need to decide on versatility (zoom lenses) or fastest possible glass (prime lenses). An over-simplification for the most part, but the point remains.