Add to Favorite Sellers. 17-40mm ultra-wide-angle zoom lens with f/4 maximum aperture for Canon SLR cameras. 3 aspherical lens elements and super UD glass element create superior optics in all conditions. Superb optical performance throughout the zoom range. Fastest AF speed within its class (same as the EF16-35 f/2.8L USM). Highly dust and moisture resistant. […]