The Mir-20 20 mm f/ 3.5(Russian: "Мир") (export version - the Mir-20) is an interchangeable superwide-angle fast lens with a single-layer coating. It also came in the variant with multi-coating (MC).
It is equipped with an automatic iris aperture, switchable in screw mount version.
It was manufactured by the KMZ in the following variants: the Mir-20M, the MC Mir-20M (m42 screw mount) and the MC Mir-20K (the Pentax K bayonet mount, small lot issued in1992). It was impossible to use front-mounting filters and attachments with these variants of the lens. The filter was installed in the rear part (the lens came with a set of three filters: UF-1x (ultraviolet), Zh-2x (yellow), O-2.8x (orange)).
The lenses were manufactured by the Arsenal Factory for some other cameras as well: the Mir-20-Automatic (for the Kiev camera) and the MC Mir-20N (for the Nikon F bayonet mount). It was possible to use front-mounting filters and attachments with these variants of the lens. Besides, the minimum aperture value of these lenses was f/16, and not f/22.
The optical scheme of the Mir-20 20 mm f/ 3.5 was based on the Carl Zeiss Jena Flektogon 20 mm f/2.8 (GDR). However, there were some changes made in the scheme.
The lens produces sharp image especially at the frame center from f/3.5 onwards, and it is very sharp from f/ 5.6. There is a considerable drop in resolution on the edges of the frame.
The Mir-20 20mm f/3.5 has virtually no geometrical distortion.
Color rendering is bright and saturated, slightly shifted towards warm colors.
The versions without MC do not hold back and side light well, whereas their counterparts with multi-coating (MC) do hold it well.
The characteristics of the Mir-20 20 mm f/ 3.5
Diagonal angle of view: 96°
Resolution: (0/10/20 mm) 1): 50/35/30 lpmm
Resolution according to the technical specifications (center/edge): 50/20 lpmm
Coefficient of transparency: the Mir-20М - 0.75; the MC Mir-20М - 0.90
Color contribution index (CCI): the Mir-20М - 11-0-2; The MC Mir-20М - 11-0-0
Geometric vignetting: 40%
Length with caps: the Mir-20М - 68 mm.: the MC Mir-20М - 63 mm.
Maximum barrel diameter: the Mir-20М - 92 mm.; the MC Mir-20М - 78 mm
Weight: the Mir-20М - 470 g; the MC Mir-20М – 390 g; the MC Mir-20K– 490 g.
The Mir-20 lens is perfectly fit for shooting landscapes, interiors, architecture, as well as for genre and reportage photography. It is easily mounted on modern DSRL cameras. When set at hyperfocal range, you can shoot very quickly without autofocus.
In the secondary market the lens is not uncommon and rather cheap. The preference should be given to MC versions of the lens, which were exported, or marked with the quality sign.