Overview

The Carl Zeiss Jena Flektogon 20mm f/4 is a super wide-angle M42 lens praised for its epoch-making retrofocus design. It offers solid build quality with all-metal construction and smooth focusing. Optically, it is decent when stopped down to f/8 or f/16, but wide open at f/4 it is softer and shows more vignetting compared to the f/2.8 version. It suits landscape and architecture photographers who can use a tripod and stop down, and is an affordable entry into vintage Zeiss wide-angles.