Canon EF 200-400mm f/4L IS USM Extender 1.4x is a telephoto zoom lens with a built-in switchable teleconverter.
The super telephoto lens is designed for professional sports and wildlife photographers and the EF 200-400mm f/4L IS 1.4x lens is currently priced at $11,999.
ePhotozine has posted sample images shot by the new Canon EF 200-400mm f/4L IS USM Extender 1.4x lens. The gallery of sample images taken with the Canon EF 200-400 mm f/4 L IS USM EXT 1.4x lens mounted on Canon EOS-1D X camera.
Canon EF 200-400mm f/4L IS 1.4x Sample Images
From ePhotozine article:
Focus was extremely fast when used in combination with the Canon EOS 1D-X, with AF tracking enabled to keep track of the high speed planes at the airfield.
Canon EF 200-400 f/4L IS USM 1.4x Price and Availability
See more sample images: Canon EF 200-400mm f/4L IS USM Extender 1.4x Sample Images