The Industar-50 is one of the most successful Soviet made lenses. It was a standard or optional lens on practically every Zorki camera, from Zorki-C in the mid 50's to Zorki-4K in the mid 70's. The lens was also made in a 39mm and 42mm SLR mount and was installed (standard or optional) on every Zenit model as well, from Zenit-C to Zenit-E. It came in different shapes and finishes, from a chrome collapsible Elmar-style lens to a black "flat" Zenit lens. The Industar-50 was also a popular enlarger lens. The optical formula was always the same (Leitz Elmar 50/3.5), the lens produced sharp and contrasty images.
The first digits of the serial number are a year prefix (5=1955, 6=1956, 7=1957, 8=1958, 59=1959).
This pictured Industar-50 is the Elmar-type collapsible version. It was primarily used on the Zorki-5, but was also sold separately.
Focal length: 52,48mm (I-22 is 51,39mm)
Angle of coverage (35mm film): 45 degrees (I-22 is 46 degrees)
Focusing: 1m - Infinity
Aperture markings: from 3.5 to 16
Formula: 4 elements in 3 groups, Tessar
Optical registration (back focus): 28.8 ±0.02mm
Mount: M39x1mm. The lens mounts and RF couples with any Leica or Leica copy (FED, Zorki etc.)
Filter size: 36mm slip-on type