Canon EF 20-35mm f/3.5-4.5 USM Ultra Wide Angle Zoom Lens for Canon… Type: Wide Angle Zoom Lens. Maximum Aperture: f/3.5-4.5. A very practical ultra-wide-angle zoom. The large front lens group minimizes peripheral darkening, and the flare-blocking diaphragm minimizes flare. Also, with lens group 2 being the zoom group, distortion is corrected. A superior performance ultra wide angle zoom lens, covering the entire range of popular wide-angle focal lengths. A ring-type USM and an inner focus design provide fast and silent AF, along with full-time manual focus override. Priced within the range of serious photo enthusiasts, its a great all-around choice. EF mount; ultra wide zoom lens. Inner focusing; full time manual focus. 20 35mm focal length. F/3.5 4.5 maximum aperture. Ring type UltraSonic Motor (USM). Focal Length Description: 20-35 millimeters. Lens Type: Wide Angle. Compatible Mountings: Canon EF. Camera Lens Description: 35 month. Product Dimensions: 5.2 x 4.6 x 4.5 inches. Item Weight: 12 ounces. Item model number: 2545A003.