Carl Zeiss Jena's Flektogon 20mm f/2.8 — a fast, close-focusing East German M42 ultra-wide.
The Carl Zeiss Jena Flektogon 20mm f/2.8 is an East German fast ultra-wide-angle prime made in M42 mount from the mid-1970s. It was the faster successor to the f/4 Flektogon 20mm, part of the celebrated Flektogon retrofocus line from the Jena works, and is one of the most sought-after CZJ wide-angles.
This is a manual-focus M42 screw-mount lens with a 20mm focal length and a bright f/2.8 maximum aperture. Focus and aperture are set by hand on the barrel and it is an all-metal retrofocus wide-angle noted for very close focusing. Detailed element and filter figures are not asserted here beyond the verified focal length and aperture.
At a fast 20mm the Flektogon gives a wide rectilinear view usable in lower light, suited to landscapes, architecture, interiors and street work. The Flektogon line is famous for notably close focusing, allowing dramatic wide-angle close-ups, and for its characterful yet sharp rendering, making this a prized classic ultra-wide.
Used copies are among the more valuable CZJ lenses and command strong prices. Inspect the front element for scratches, haze and fungus, confirm the aperture blades are clean and oil-free, and check the aperture-ring and focus feel, which should be smooth. Verify the M42 mount. An M42 adapter makes it a highly regarded wide-angle on mirrorless.