Designed to extend a lenses focal length by a factor of 2x the redesigned canon extender ef 2x iii delivers optical performance on par with the finest canon super telephoto lenses it features a built in microcomputer for seamless communication among camera body lens and extender features careful lens placement and coatings to minimize ghosting flare and chromatic aberration and even has a new fluorine coating that keeps soiling smears fingerprints to a minimum