The new EF 200-400mm f/4L IS USM EXTENDER 1.4× is currently in development with Canon hoping to release it before the end of the year. Designed to be used with Canon's EOS digital SLR cameras, the telephoto zoom lens will "be an ideal addition for sports and wildlife photographers, claims the firm.

The integrated extender, which has been fine-tuned for the lens' focal length, will create an increased focal range of 280 to 560mm.

The lens will go on display at the CP+ trade show in Yokohama, Japan this week. It remains unclear whether it will make an appearance at this year's Focus On Imaging trade show in Birmingham.

Meanwhile, Canon has released more details about its previsouly-announced new super-telephoto lenses - the EF 500mm f/4L IS II USM and the EF 600mm f/4L IS II USM.

"Designed to meet the needs of the most demanding sports and wildlife photographers, both lenses offer breakthrough performance, delivering consistently high-quality images and incredible mobility," says Canon.

Both lenses will replace their predecessors - the EF 500mm f/4L IS USM and EF 600mm f/4L IS USM. The new models feature the latest Canon Image Stabiliser technology, with magnesium alloy constructions that includes titanium components "to make each lens significantly lighter and even more durable," says Canon.

In fact, the 600mm model is 27% lighter than its predecessor, weighting 1.4kg. The 500mm, meanwhile, weighs 680g less than its predecessor.

Both lenses feature 16 elements in 12 groups, as well as Canon's Super Spectra Coatings and a SubWavelength Structure Coating, "optimised to effectively reduce ghosting and flare," says Canon. "A water-repellent fluorine coating is also used on the surface of the front and rear elements, repelling dust and dirt for clearer shots, and keeping the front element free of marks by ensuring water droplets run off the lens quickly."

The two lenses use Canon's latest Image Stabiliser system, which allows photographers to shoot at speeds up to four times slower than normally required, according to Canon. "IS Mode 2 features new algorithms to improve performance when panning, and the new IS Mode 3 is also included, assisting users when switching between subjects by activating the IS unit only during exposure."

The new models benefit from rapid, quiet auto-focus thanks to a ring-type Ultrasonic Motor.

Both lenses also feature a revised layout, with "carefully-positioned controls that improve everyday operation," claims Canon. "The AF stop buttons are now location-adjustable, improving ergonomics by allowing users to custom-select the position of the lens grip where the AF stop buttons are located."

The EF 500mm f/4L IS II USM will be available from mid 2011, priced at £8999/€10,799. 

The EF 600mm f/4L IS II USM will also be available from mid 2011, priced at £11,299/ €13,549.