The Canon EF 135mm f/2L USM is a short-to-medium telephoto lens. The "135/2" is mainly used for portrait photography and for indoor sports, where the lighting is often poor. The fast f/2 aperture makes the lens ideal for both of these applications. The EF 135mm f/2L USM lens offers internal focus; the length does not change while focusing. The lens is compatible with the Canon Extender EF teleconverters.