Carl Zeiss Jena's Flektogon 20mm f/4 — a respected East German M42 ultra-wide prime.
The Carl Zeiss Jena Flektogon 20mm f/4 is an East German ultra-wide-angle prime made in M42 mount from the early 1960s. Part of the respected Flektogon retrofocus wide-angle line from the Jena works, it was one of the wider offerings in the CZJ M42 range and is well regarded among vintage wide-angles.
This is a manual-focus M42 screw-mount lens with a 20mm focal length and a maximum aperture of f/4. Focus and aperture are set by hand on the barrel and it is an all-metal retrofocus wide-angle. Detailed element and filter figures are not asserted here beyond the verified focal length and aperture, in line with the accuracy standard.
At 20mm the Flektogon delivers a wide rectilinear view for landscapes, architecture and interiors, and the Flektogon line is noted for close focusing and controlled distortion for its era. It renders with the characterful yet capable quality associated with Carl Zeiss Jena wide-angles, making it a favourite classic ultra-wide.
Used copies are sought after and priced above the standard CZJ primes. Inspect the front element for scratches, haze and fungus, common in older Jena glass, confirm the aperture blades are clean and free of oil, and check the aperture-ring and focus feel. Verify the M42 mount. An M42 adapter makes it a well-liked wide-angle on mirrorless.