The Canon EF 16-35mm f/2.8L II USM Autofocus Lens is a high performance, water-resistant, and ultra wide-angle L-series lens. The optical design has been improved to offer better edge-to-edge image quality. In addition, it features 3 high-precision aspherical lens elements, each of a different type: ground, replica and GMo. Improved AF algorithms will help the lens to focus faster and quieter.