Carl Zeiss Jena's long Exakta tele — the Sonnar 300mm f/4 for reach and distance work.
The Carl Zeiss Jena Sonnar 300mm f/4 is a long telephoto prime from Jena, the far end of the Exakta bayonet system's reach. It was a large, specialist lens aimed at wildlife, sport and long-distance work, and relatively few Exakta owners bought one given its size and cost. It represented the top of the CZJ telephoto line offered in the mount.
This is a manual-focus Exakta-mount lens with a 300mm focal length and a maximum aperture of f/4. It uses a Sonnar-type telephoto design and is a large, heavy lens usually fitted with a tripod mount. The aperture is set on the barrel and coupled through the Exakta mechanism on supporting bodies. Weight, element count and filter thread are left out here where they cannot be confirmed for the specific Exakta variant.
The Sonnar 300mm f/4 brings distant subjects close and, at f/4, keeps a usably bright viewfinder for a lens of this length. It suits wildlife and field sport where the reach is needed, and general long-distance detail work. Because of its size it is best used from a tripod or firm support, and stopping down a stop improves contrast and edge definition for critical work.
This is a bulky and comparatively rare lens, so used examples are few and prices reflect scarcity. Inspect the large front element carefully for haze, fungus, separation and coating damage, all of which are costly to remedy at this size. Check the aperture, the long focus helicoid and the tripod collar for smooth operation and no play. On mirrorless via an Exakta adapter it is a heavyweight manual tele needing solid support.