If you own a camera, you own a lens. (If you own a pinhole camera, be quiet.) Whether it comes off your camera or doesn't, zooms or has a fixed focal length, has glass elements or plastic - the lens and sensor are the most important elements of your camera set-up.
But don't tell that to your tripod head and hotshoe.
One of the most common gear-related questions we see in the Photography Forum and :#photographers: chat is, "What lens do I need to shoot [image X]?" You'd think it's an easy one to answer, but it really isn't. Today I'm going to try to explain the various things that make a lens good, and go over some of the more common lens types and their applications.
Consider yourselves warned: This will be dry at times. This will read like a physics textbook at times. It may cause uncontrollable bowel movements, I don't know, maybe you have some psychological co