The basis of the optical design of the lens was taken from the Carl Zeiss Jena Flektogon 20mm f / 2.8 (DDR). Some changes have been made to the scheme.
Focal length 20 mm.
Aperture ratio 3.5.
Aperture type - iris.
Aperture blades 6.
Maximum aperture 3.5.
Minimum aperture 16.
Minimum focusing distance 0.18 m.
Number of lenses / groups 9/8.
Viewing angle 96 °.
Resolution center edge 50/20 mm.
Threaded mount to the M42 camera.
Filters thread 28mm.
Weight 390 g.
Ergonomics and design:
The lens is completely made of metal and glass. The focusing ring of Mir-20M rotates approximately 180 degrees and there is an infrared shift mark on the lens. Also, the lens has a minimum aperture of F / 16. MDF is the same 18cm. Mir-20M 3.5 / 20 does not have a thread for light filters in front of the lens, but they can be screwed into the thread near the rear lens of the objective.
Mir-20M 3.5 / 20 - has impressive dimensions and an interesting convex front lens, looks very unusual on the camera. The protective front cap simply slips snugly onto the lens.
Artistic features and photo examples:
The lens produces a sharp image, especially in the central area, already from aperture 3.5, from aperture 5.6 it is very sharp. The drop in resolution at the edges of the frame is quite noticeable. The Mir-20M 20mm f / 3.5 has almost no geometric distortions. Color reproduction is bright, saturated. Slightly shifted to the area of warm colors. This version with multi-coating - holds back light quite well.
The Mir-20M lens is perfect for shooting landscapes, interiors, architecture, genre and reportage. Works well on modern digital SLR cameras.
Mir-20M is an excellent ultra-wide-angle lens that is suitable for shooting landscapes, interiors, architecture, genre and reportage. Produces a sharp image, shows good color rendition.