Increases the focal length of Canon L-series telephoto and telephoto zoom lenses by 2x, e.g. a 300mm f/4 lens becomes a 600mm f/8. Latest III version.

The Canon Extender EF 2x III telephoto extender increases the focal length of Canon's L-series telephoto and telephoto zoom lenses by 2 times, e.g. a 300mm f/4 lens becomes a 600mm f/8.
EF 2x III reduces the light output by two stops - recommended only for fast telephoto lenses (for lenses with f/2.8 or f/4 apertures).
The III model has improved weather resistance with fluorine-coated lenses. In addition, internal reflection suppression has been improved, AF works better, and communication with the latest bodies works better.