The Canon Extender EF 2X III is designed for select Canon EF mount L-series telephoto lenses. It increases the focal length of a lens by a factor of 2x while still delivering superb image quality. To ensure the best possible image quality in all shooting conditions, it combines redesigned optics, improved data communication between lens and camera and enhanced environmental protection. It is ideal for photojournalists and wildlife, nature and sports photographers who need to get close to distant and challenging subjects and it reduces the need to carry heavy telephoto lenses. The Extender EF 2x III features nine optical elements in five groups, ensuring improved optical performance. All optical elements have Canon's Super Spectra coating to reduce ghosting and flare. A new Fluorine Coating on the front and rear elements makes marks, such as spots left by water or fingerprints, much easier to clean than standard coatings. To facilitate the accurate transfer of imaging data between the lens and camera body, the extender features an integrated processor which ensures all focusing, metering and ID information is available - allowing the photographer to capture balanced, well-exposed images. When combined with the latest range of premium Canon L-series lenses, these extenders enable AF accuracy even when capturing moving subjects. When attached, the 2x extender reduces the effective maximum aperture by 2 stops. A carefully positioned lens release mechanism also makes it easy to mount the extenders quickly, reducing the time that the camera and lens are exposed to the environment. The extenders offer the exceptional build-quality expected from Canon's professional products, and are resistant to both dust and water, allowing photographers to use them in extreme shooting conditions.