The Canon 135mm F/2 L USM is a superior lens for shallow depth of field and low light situations. It is a great choice for nature and portrait photography. It features two UD-glass elements to remove aberrations and gives the lens an excellent level of sharpness across the focusing range.
This lens features a maximum aperture of F/2 which allows for great subject separation and beautiful portraits. It also features Canon's USM (Ultra Sonic Motor) drive for fast silent focusing.