The Zeiss 210mm f4 Sonnar is the second-longest lens in the Contax 645 system, behind only the ultra-rare 350mm f4 Tele-Apotessar. With an equivalent focal length of 130mm in the 35mm format, it is an excellent choice for head-and-shoulders portraiture and other applications that require close cropping and compression. Despite being noticeably longer than other lenses in the Contax 645 system it handles well when mounted, especially with the MP-1 battery grip attached. Autofocus performance, while not as fast as shorter lenses such as the 80mm f2 Planar, is nevertheless effective and can be fine-tuned manually without switching to the manual focus mode. As with all lenses in the Contax 645 system, the Zeiss 210mm f4 Sonnar has all-metal construction that exudes quality and durability. Overall, the Zeiss 210mm f4 Sonnar is a critical addition to any Contax 645 kit.