optical performance for a professional standard zoom lens. It has one Super UD lens element and two UD lens elements that minimize chromatic aberrations in the periphery at wide-angle, as well as reducing color blurring around the edges of the subject. In addition, two types of aspherical lenses are combined to help reduce spherical aberration over the entire image area, as well as through the full zoom range. Optimized lens coatings help ensure exceptional color balance while minimizing ghosting.
A ring-type USM and high-speed CPU with optimized AF algorithms ensure silent, fast autofocusing. The lens is constructed with improved dust sealing and water resistance, while fluorine coatings on the front and rear lens reduce fingerprints and smearing. A circular 9-blade diaphragm gives beautiful, soft backgrounds. A zoom lock lever locks the zoom position at the wide end for safe transporting while attached to an EOS DSLR camera over the shoulder.