The EF 135mm f/2L USM is a medium telephoto prime and a member of Canon's L-series of lenses. The long focal length coupled with the f/2 maximum aperture afford a great deal of control over depth of field for isolating subject matter and using selective focus, and the bright aperture also benefits shooting handheld in low-light conditions. In regard to the optical design, the lens uses two ultra-low dispersion elements to control chromatic aberrations and colour fringing for high clarity, and a Super Spectra coating has also been applied to suppress flare and ghosting for increased contrast and colour accuracy. Complementing the imaging attributes, a ring-type USM is employed to deliver quick and quiet autofocus performance along with full-time manual focus control.