The EF 16-35mm f/2.8L II USM is a high performance, water-resistant, and ultra wide-angle Canon L-series lens. It has been specifically designed for improved edge-to-edge image quality that will meet the strict requirements of professional and high-end amateur photographers. It features 3 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