This L-series lens has been specifically designed for improved edge-to-edge image quality to meet the strict requirements of professional and high-end amateur photographers. It features three high-precision aspherical lens elements, each of a different type – ground, replica and GMo – for even better image quality than the original EF 16-35mm f/2.8L USM. The circular aperture produces a beautiful and natural background blur when shooting at wider apertures. Other features include internal focusing, a ring type USM (Ultra Sonic Monitor), and new AF algorithms for fast and quiet autofocusing.