Industar's compact Tessar-type fifty — 50mm f/3.5 in M39, crisp and pocketable, very cheap used.
The Industar-50 is a Soviet standard lens of Tessar type, made for the M39 (Leica thread) rangefinder mount and used on FED, Zorki and Leningrad bodies. It is one of the small, flat Industar standards of its generation, carrying the four-element Tessar lineage in a very compact barrel, and it also exists in an SLR mount version for Zenit bodies.
This is a manual-focus, rangefinder-coupled Leica Thread Mount lens with a 50mm focal length and an f/3.5 maximum aperture. It uses the 39mm rangefinder thread and mounts on Leica screw bodies, subject to the slight Soviet-versus-Leica register difference. Its Tessar-type construction and modest aperture make it one of the more pocketable standard lenses in the Soviet M39 range.
Tessar-derived rendering gives the Industar-50 crisp, contrasty images when stopped down a little, with a flat, even field that suits general, travel and street work. The f/3.5 aperture keeps depth of field forgiving and the barrel small. It is a compact everyday standard whose appeal is classic Tessar sharpness rather than a distinctive bokeh character.
On the used market the Industar-50 is among the cheapest capable Soviet standards, offering strong value for money. Soviet QC varied by year and factory, so evaluate each sample individually. Adapting to Leica may need a register check or shim. Inspect for haze and coating scratches, feel the aperture ring, and test the focus action for smoothness. It adapts readily to mirrorless with an M39 adapter, where its small size is an asset.