Industar I-51 - is a lens from the "FK" wooden camera, designed for a 13x18 cm format. A similar camera was used in Soviet photo studios and pavilions to shoot films
The optical scheme is a classic retrofocus Tessar. This is a scheme in which the back segment of the lens is approximately equal to the focal length.
The lens is a small cylinder with a diameter of 60 mm and a length of 53 mm.
In the middle, a metal diaphragm control ring, which smoothly closes. Like all large-format lenses, Industar-51 does not have a focus mechanism.
To install the I-51 on the modern camera, it will be necessary to compensate for its long working segment (183.71 mm). And also supply it with a focus mechanism. (Please look at the penultimate photo)
Industar-51 has a non-standard landing thread M60x0.75.
By the way, the front diameter allows you to close the lens with a standard 52 mm lid, it is ideal for this. (please, look at the last photo)
Manufacturer: Kazan Optical and Mechanical Plant (KOMZ)
Minimal Aperture - f/4.5
Maximal Aperture - f/32
Focal length - 210mm
Mount - M60
S/N - 660074
Number of diaphragm petals: 20 pcs
Made in USSR (1966)