Super Telephoto Lenses
Attaching this high-performance Extender to a 135mm or longer lens or to the EF 70-200mm f/2.8L boosts the focal length by 1.4 times. With five elements in four lens groups, it preserves the prime lens’ image quality.
With the Extender attached, the f-number decreases by one stop. Autofocusing is also possible with lenses whose maximum aperture is f/4 or faster.