Using the right lens is arguably the most critical part of your photographic setup. It's the optical quality of the lens, not the camera's resolution, that determines how sharp your images are. It's the lens that governs how much of the scene you're shooting is in focus, because it's primarily the lens aperture that dictates the depth of field. Crucially, it is also the lens's focal length that determines whether you capture a wide vista or a close-up of a distant subject.
Here we'll explain what focal length is and how it determines what part of the scene is captured by the camera, and explore focal length related terms such as prime, zoom and telephoto.