Pre-PMA 2008: As part of Sigma's bumper lens launch, it has announced what might be the ultimate wildlife lens. Sigma claims the APO 200-500 f.2.8 is the world's first lens to offer an f/2.8 aperture at 500mm focal length. It comes with an "attachment" to give users a handy 400-1000mm f/5.6 option. The lens (which is cosmetically reminiscent of a piece of military hardware) weighs nearly 16kg and uses a dedicated Li-ion battery to provide power for focusing and zooming. It will be available in Sigma, Canon and Nikon mounts.

Source: News: Digital Photography Review (dpreview.com)