Extending a lenses focal length by a factor of 1.4x, Extender EF 1.4X III incorporates phenomenal optical performance with minimal chromatic aberration and is a perfect complement to many of Canon super telephoto lenses. The Fluorine coating resists soiling, smears and fingerprints. Extender EF 1.4X III maintains high standards not only optically, but also in terms of rugged, dustproof and water resistant construction.