The EF 16-35mm f/2.8L II USM is a high performance, water-resistant, & ultra wide-angle Canon L-series lens. It has been specifically designed for enhanced edge-to-edge image quality that will meet the strict requirements of professional & high-end amateur photographers. It features 3 high-precision aspherical lens elements, each of a different type: ground, replica & GMo for even better image quality than the original EF 16-35mm f/2.8L USM. The circular aperture produces a beautiful & natural background blur when shooting at wider apertures. Other features include internal focusing, a ring type USM (Ultra Sonic Monitor), & new AF algorithms for fast & quiet autofocusing. Offers better optical performance over older model & better resolution than 17-40 at equivalent aperture Additional element giving better edge to edge performance The performance is much closer between f/2.8 & f/8 throughout the frame Same level of moisture/dust resistance New 82mm diameter filter Slightly larger & heavier than before Circular aperture for pleasing Bokeh (background blur)