KMZ Mir-24M 35mm f/2

Put a Mir-24M on a Zenit and the camera tips forward on its strap. At 370 grams it is heavy for a 35mm wide, and the 58mm filter thread tells you how much glass sits behind the front ring. People carried it anyway, because at f/2 it was a full stop faster than the f/2.8 Mir-1 that was the usual Soviet 35-ish wide for M42. For anyone shooting interiors on fast film, that stop was the whole point.

GOI, the state optical institute, calculated the design and patented it in 1970. KMZ only put it into small-series production in 1976, and the phrase is accurate: you see these far less often than the Helios-44 that came on most Zenit kits. Inside are eight elements in seven groups. The field covers 66 degrees, a touch wider than a 35 feels on paper, and the lens focuses down to 0.3 m. At that distance a coffee cup takes up a good part of the frame, with plenty of the table still showing.

What separates it from the Mir-1B or the M42 Jupiter-9 is the diaphragm. Those keep preset rings; the Mir-24M has a pin-actuated automatic diaphragm with a manual/auto switch on the barrel. On a body that presses the pin, you focus and frame at f/2 and the blades close only when the shutter fires. On an older body, or an adapter that leaves the pin alone, flip the switch to manual and the lens stops down as you turn the ring, so stop-down metering works normally. No setting a preset, opening up to focus, then remembering to close down again before every frame.

Owners generally describe it as a lens that is good in the middle and weak at the edges wide open. The centre holds detail at f/2, the corners lose sharpness and contrast, and a bright source near the frame can veil the shadows. Most reports have it clean across the frame by f/5.6 to f/8, which is where black and white street shooters tend to leave it in daylight. Where it earns its weight is close and wide open: a subject at half a metre against a busy room, with the background falling away softly behind.

Bulk is the price. Next to the Pentax Super-Takumar 35mm f/2, which most M42 shooters look at first, the Mir offers the same f/2 speed, and it tends to cost less. Production ran about ten years. A 1986 KMZ order ended the multicoated MC Mir-24M, cancelling the Industar-50-2 and the Zenitar-M at the same time. Arsenal's Vega factory also made a Nikon F sibling, the MC Mir-24N, with the same optical design in a different barrel; the M42 version is the one you will find on Zenits.

In dim rooms, set Zone Light Meter to f/2 and take readings with the lens wide open. A kitchen at EV 5 (ISO 100) gives about 1/30 second at f/2 on ISO 400 film, slow but holdable with a 35. On a body that presses the pin, leave the switch on auto and the viewfinder stays bright while you focus.