The unique Canon EF 200-400mm F/4L IS USM 1.4X Extender lens is now finalized after being showed in prototype-form last year. The super-telephoto zoom introduces a new twist to high-performance telephoto lenses by including a 1.4X extender built right into the lens barrel.
In what is now the most complex lens to describe yet, Canon has created an extremely versatile product. With the extender disengaged, this is a constant aperture 200-400mm F/4 zoom. It covers an angle of view of 12° at the wide-end and 6° at the long end. The aperture can be stopped down to F/32 from there which gives an extensive depth-of-field but is beyond the diffraction limit of all current Canon DSLRs.
With the extender engaged the lens becomes a 280-560mm F/5.6 super-telephoto lens with a minimum aperture of F/45. In this mode, it covers an angle-of-view between 8.5° and 4.25°. The minimum focus-distance, regardless of extender is 2m.
One can see this lens as a 200-560mm F/4-5.6 with an odd stepping of maximum aperture. It can also be combined with an external 1.4X or 2X extender for even more reach at the expense of image-quality and loss of light.
This super-telephoto offering is full weather-sealed and accepts 52mm drop-in filters at the rear. In inner ultra-sonic focus system lets if focus quickly and quietly. The lens is made of 25 elements arranged in 20 groups and the extender is made of 8 elements in 4 groups, making it one of the most complex lenses every designed.
As expected by such a long lens, it is optically stabilized with 4-stops of improvement claimed. At 3.6kg, this lens is most likely going to find a permanent home on a tripod.