A versatile, fast aperture telephoto lens for both digital and film SLR cameras. Two ELD glass elements reduce chromatic aberration to a minimum and also ensure sharp, quality images of high contrast. The new multi layer lens coating reduces flare and ghost, which is a common problem with digital SLR cameras. The overall length of the lens does not change during focusing, ensuring convenient handling and ease of use. The Internal Focus system ensures the overall length of the lens does not change during focusing, ensuring convenient handling and ease of use. The HSM (Hyper Sonic Motor) models provide fast, silent AF function as well as full- time manual focus override. A drop-in 46mm filter holder in the rear part of the lens barrel can be rotated to facilitate the use of filters, including a polarising filter, in situ. Simply adding an APO teleconverter (optional extra), means that this lens can be used as a 420mm F4 AF ultra-telephoto lens with a 1.4X EX teleconverter, or a 600mm F5.6 AF ultra-telephoto lens with a 2X teleconverter.