The EF 200–400 mm f/4L was first announced to be in development in February 2011 and a prototype was showcased at the 2011 CP+ tradeshow.[1] In November 2011, Canon announced that availability of the lens would be postponed to an unspecified later date.[2] The lens was only released more than a year later in May 2013.[3]
Built-in 1.4× Extender
Although not the first lens to be equipped with a built-in teleconverter, an honor that belongs to the older Canon FD mount 1200 mm f/5.6L 1.4× lens,[4][5] the EF 200–400 is the first to be for the EF mount, and the first to enter mass production. The extender, when engaged, increases the lens' focal length by a factor of 1.4×, while decreasing the aperture by a single stop, changing the lens to a 280–560 mm f/5.6 lens. The extender is activated and deactivated by a mechanical switch close to the lens mount.
