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.
This tele extender can be used with fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, 70-200 f/4.0L IS USM, and 100-400 f/4.5-5.6L IS zoom lenses. Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x. Effective aperture is reduced by one f-stop; autofocus is possible on any EOS camera when combined with a lens having an f/4 or faster maximum aperture.