Voigtlander Ultra Wide-Heliar 12mm F5.6 Aspherical III

Reviewers found most of the frame sharp at f/5.6 and the outer edges acceptable by f/8, with diffraction setting in from f/11. Distortion is low and easy to profile out, flare resistance is very good, and sunstars are attractive from f/5.6 onwards.

Vignetting is the major flaw, at close to three stops on older A7 bodies, and a slight colour cast can show on even tones such as snow or sky. It is regarded as a well-balanced, pleasant lens for users who find 10mm too wide.

Owners like it for hiking, architecture and travel because it is small, solid and much lighter than a 12-24mm zoom. The scale-focus workflow at f/8 suits street and landscape shooting.

The common gripes are dark corners that need profile correction, no way to mount filters, and an exposed front element. Since it went out of production, used copies are the usual route and prices vary widely.