800mm · f/5.6
The Leica APO-Telyt-R 800mm f/5.6 is a modular telephoto lens with apochromatic correction and internal focusing, part of a system that can combine front and end elements to yield multiple focal lengths. It offers very good image quality with wide fabrication tolerances, as per the patent by Lothar Koelsch. The lens is manual focus and suited for nature shooting, but no weaknesses or handling issues are mentioned in the excerpts.