Nhân đôi tiêu cự cho tele và tele zoom. Hạn chế 2 Khẩu độ khi lắp (f:2.8>f:5.6).

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. EXTENDER EF 2X III MEETS NECESSARY STANDARDS IN TERMS OF RUGGED, DUSTPROOF AND WATER-RESISTANT CONSTRUCTION, AND SHOULD BE IN EVERY PROFESSIONAL'S CAMERA BAG.