The EF 24-70mm f/4L IS USM Lens from Canon is optimized for full-frame 35mm sensors, and another entry into Canon "s high quality L-series of lenses. It has two Super Ultra-low Dispersion (Super UD) and two standard UD lens elements working together to minimize chromatic aberrations, and reduce color blurring around the edges of your subject. Its two types of aspherical elements combine to help reduce spherical aberration over the entire image area and the full zoom range. Optimized lens coatings help ensure exceptional color rendering while minimizing ghosting. Its ring-type Ultra Sonic Motor (USM) and high-speed CPU, with optimized AF algorithms, ensure you experience quick, quiet and precise autofocusing whenever you need it. The lens has improved dust and water resistance to protect it from damage outdoors, while fluorine coatings on the front and rear lens surfaces resist fingerprints and smearing. The circular nine-bladed diaphragm delivers beautiful, soft background effects. A zoom lock lever holds the zoom position at the 24mm wide end for safe transporting while attached to an EOS DSLR camera over the shoulder - preventing lens creep.