Industar 61

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The Industar 61 was produced at the FED factory in Kharkov, Ukraine. It is a "normal" lens for M39 (Leica screw mount) and M42 (Pentax screw mount), with a focal length from 52-55mm, depending on the production run. It has four elements in three groups. The iris may have between six and ten blades depending on the version of the lens, and a range of apertures from f/2.8 to either f/16 or f/22. It is commonly found on rangefinders made by FED and Zorki. Its brand name Industar refers to the class of similar 4-element/3-group lens constructions of the whole soviet photo-optical industry.

The Industar 61 L/D is possibly the most highly regarded lens for Ukrainian Leica copies apart from the 35mm Jupiter-12. In an L/D or L/Z version of this lens, the L indicates that the lens has (slightly radioactive) Lanthanum in it, and D indicates M39 mount while Z indicates M42 mount. Most examples are multi-coated and are marked as such with MC. Some Industar 61 L/Z bear the logo of LZOS, probably having been made by that company.

Optical formula from OPAL database

 Cистема-Индустар-61  f'=53   2w=46 1:2.8

  N      Радиусы       Осевые     Световые   Марки     Показатели преломления 
 пов.   кривизны       расст.      высоты   стекол
                                                 L=   .589300   .434050   .656280

   1      19.099        7.500       9.300      СТК9  1.742397  1.761307  1.738057
   2      57.540        1.500       8.000    ВОЗДУХ
   3     -80.170        1.600       8.000        Ф4  1.624200  1.647216  1.619252
   4      16.106        3.800       7.400    ВОЗДУХ
   5      84.140        1.500       7.600       ЛФ9  1.579999  1.600239  1.575648
   6      19.099        7.000       7.700      СТК9  1.742397  1.761307  1.738057
   7     -40.460                    8.070    ВОЗДУХ

 ПРЕДМЕТ: Удал. размер Y = -23.00000гр.мнсек S0=    .000дптр от вх.зрачка 
 ИЗОБРАЖ: Близ. размер Y'=    .00000         плоск. SI=    .000мм   от пл.Гаусса
 ДИАФР. : ND=  4  плоскость    SD=   2.0000 мм  передн. апертура=   9.3000 мм