Yongnuo YN-2.0X III teleconverter is an excellent alternative to the Canon EF 2X III extender offering very similar performance for few times less price. Yongnuo’s version like Canon’s also packs 9 lens elements into 5 groups and reduces the lens maximum effective aperture by two stops. This is common for 2X extenders, while 1.4X extenders Forget using an extender on the 55-250, unless you don't mind to focus manually. Second, the 70-300 will give you better better results than a 55-250+extender. Third, I doubt if there are any extenders that fit EF-s lenses. Kind regards, Sandor. maarensv's gear list: Canon 6D Mark II Canon EOS R Olympus E-M5 III Canon EOS R7 Canon EF 100mm F2 Announced Aug 26, 2010. Discuss in the Canon SLR Lens Talk forum. Manufacturer description: 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 Learn more with 3 Questions and 4 Answers for Canon - Extender EF 2x III Extender Lens - Multi. User rating, 4.9 out of 5 stars with 5130 reviews. (5,130) Built for all environments. This extender boasts a coating around the outer edges of the lens elements to reduce flare. Let the lens and camera do the talking. EF Extender 1.4x III's in-built microprocessor provides accurate transfer of data from the lens and camera every time, everywhere. The following disclosure statement is added to this Service Contract: If You have any questions regarding this Service Contract, or a complaint against the Obligor, You may contact the South Carolina Department of Insurance at 1201 Main Street, Suite 1000, Columbia, South Carolina 29201, (803) 737-6160. "Kleine Teles": Erstaunlich schnell fokussiert die Kombi 2x III mit dem Canon EF 300mm 1:4,0 L IS USM Objektiv (77 mm Filtergewinde) an der 5D III (Firmware 1.2.1!), ditto mit meinem Canon EF 70-200mm 1:2,8L IS II USM Objektiv (77 mm Filtergewinde). Auch hier ist die optische Qualität für so einen extremen Extender recht akzeptabel. Hoje no vlog do zack o primeiro teleconversor do canal, o Canon EF Extender 2X III. Simples e fácil de usar, ele consegue multiplicar por dois a distância fo BAYsP.