Zorkiy BK 1: 2,8 F = 3.5cm P for Kiev cameras. Review from Rodion Eshmakov

Material according to K 1: 2,8 F = 3.5cm P specially for Radozhiva prepared Rodion Eshmakov (subscribe to Instagram!)

A rare prototype of the famous Jupiter-12 today, the only 35 mm wide-angle lens for Soviet rangefinder cameras with interchangeable optics.

A rare prototype of the famous Jupiter-12 today, the only 35 mm wide-angle lens for Soviet rangefinder cameras with interchangeable optics. increase.

The first post-war lenses, made on German equipment and, possibly, glass taken out for reparations, with the help of German specialists, had simple names. Production experiments were carried out at KMZ, which was reflected in the names: BTK - "biotar Krasnogorskiy" (future Helios-44), ZK - "zonnar Krasnogorskiy" (future lenses Jupiter-8, Jupiter-9, Jupiter-3 and Jupiter-11) and BC - "biogon Krasnogorsk", the future Jupiter-12. The new optics were successfully produced in small series from ~ 1947 until 1951, when the stocks of exported optical glass ran out and the German engineers had to be released. However, it is not known for certain whether these small-scale lenses were the result of recalculations for Soviet glass made by M.D. Maltsev's group, or whether they used German glass, but were produced using technologies available in the USSR. One way or another, it is believed that the lenses of the BTK, BK and ZK series differ from the large-scale versions by other optical properties and - often - by different mechanics.

Portrait of the "chief optician" (this position did not exist yet) KMZ in the 1950s - Mikhail Dmitrievich Maltsev, 1956

Portrait of the "chief optician" (this position did not exist yet) KMZ in the 1950s - Mikhail Dmitrievich Maltsev, 1956

The hero of this article is a rare Zorkiy BK 1: 2,8 F = 3,5 cm lens - a late version of the BK lens in a frame for Kiev (Contax) cameras. "Sharp" in the name of the lens is a reference to the code designation of the KMZ plant in the communications equipment (the plant's call sign). The first version of the BK lens had the old logo of the manufacturing plant in the form of a Dove prism without a beam ("coffin") and was produced in 1947-1948. The same copy, as follows from the serial number, was made in 1950 - which is close to the date of the end of production of limited-edition variants. Then the lens was produced as Jupiter-12, the oldest representatives of which I know were released in 1952.

The history of the development of the small-format lens "Biogon" - the progenitor of Jupiter-12 - is presented in this article... It also raised a question regarding the optical design of the BK lenses: was this lens the original seven-lens Carl Zeiss Jena Biogon 35 / 2.8 (1937) in a body with the KMZ emblem, or was it already a revised six-lens version (similar to Carl Zeiss Oberkochen Biogon 35 / 2.8 (1950)? It turned out that the specimen presented in this article is a six-lens objective (the conclusion was made by the number of strong and weak reflections of a point light source from the objective lenses: bright reflections correspond to the glass-air interfaces, dim ones - glass-glue- Thus, there are two variants of the origin of the BC: either it is a lens recalculated by Maltsev using Soviet optical glass; or German experts were able to convert a seven-lens 1937 lens to a six-lens lens independently by 1947 (without Bertele's participation). uncertainty, the study of this perfectly preserved prototype of Jupi becomes more and more interesting. tera-12.

TECH SPECS

A source.: link
Optical design - "Biogon" (6 lenses in 4 groups, akin to "Sonnar"); Pinspect the diagram
Focal length - 35 mm;
Aperture ratio - 1: 2.8;
Field of view - 63 °;
Frame format - 36 * 24 mm;
Light transmission coefficient - 0.75;
Rear focal distance - 7,53 mm;
Aperture - 5 blades, no presetting mechanism;
Aperture limits - F / 2.8-F / 22;
Filters thread - 40.5 mm;
The minimum focusing distance is 1 m;
Mount to the camera - bayonet Kiev / Kontax.

design Features

My copy of the lens has a Kiev-Contax mount, an external mount. Home-made adapters made of helicoid and bayonet of dead cameras "Kiev" do not very well fix the optics of this system with an external bayonet. Therefore this lens has been redesigned with the same waythat I used to adapt Jupiter-12 to a Sony camera: for the BK I ordered a special shank with an M42 thread to connect the lens through the M42-M42 12-17 mm macrohelicoid and a 1 mm M42-NEX flange to the camera. This trick solves the most important drawback of rangefinder optics - the extremely inconvenient MDF 1 m: the adapted lens is able to focus only 30 cm from the object.

Sharp BK with a new shank worn over the native one; in 12-17 mm macrogelcoid with Sony E.

Sharp BK with a new shank worn over the native one; in 12-17 mm macrogelcoid with Sony E.

Like the original Carl Zeiss Jena Biogon 35 / 2.8, Zorkiy BK is made in a compact aluminum case. The lens unit is recessed into the body and the bayonet space due to the extremely small rear focal segment - the rear lens of the BC is very bulging, and ordinary caps do not fit it.

Sharp BK with installed M42 threaded shank. The massive rear lens unit is visible, protruding far beyond the plane of the Kiev / Contax mount.

Sharp BK with installed M42 threaded shank. The massive rear lens unit is visible, protruding far beyond the plane of the Kiev / Contax mount.

The rear lens is the most vulnerable point of this lens: if the front lens is recessed into the body and well protected from external influences, then the rear lens is not even protected by the frame, i.e. sticks out beyond its limits. Therefore, the lens should never be mounted on the rear lens unit to avoid the enormous risk of damage to the central region of the rear lens. It's also very difficult to find the covers: I have to keep the lens twisted on the MDF, because the lens sticks out strongly even beyond the plane of the Sony E mount.

The rear lens of the objective is completely defenseless, and its damage is extremely critical for the image due to its proximity to the matrix: every scratch will be visible.

The rear lens of the objective is completely defenseless, and its damage is extremely critical for the image due to its proximity to the matrix: every scratch will be visible.

The nose of the lens is the aperture setting ring aligned with the filter thread. Working with a polaric would, perhaps, be very inconvenient: when rotating it, it is easy to accidentally knock down the set aperture.

The diaphragm of the BK is the same as that of the serial Jupiter-12 - it is five-lobed, specially for stamping the “Quality Mark” introduced later on photographs. The blades of the diaphragm are covered with a matte dark paint and are rounded.

Diaphragm Sharp BK in the closed position.

Diaphragm Sharp BK in the closed position.

The lens differs from the late Jupiter-12 and the applied enlightenment: in the BK it is pale, blue and pink, having little effect on the light transmission spectrum. In the later Jupiter-12, an amber-colored coating was used, shifting the maximum transmission to the cold blue region.
Below are joint photographs of late Jupiter-12 (LZOS) and Zorky BK.

As you can see, the lenses differ somewhat in their external design. However, the early Jupiter-12 looked very, very similar to the BK: they had the same body and the same rear lens unit.

I have not been able to find any constructive advantages in the BK compared to the large-scale late Jupiter-12, although I like the fact that the rear lens unit of early Jupiters and BK is better protected. It is much more interesting to find out how they differ from each other optically. And are they different?

Optical properties. Comparison with Jupiter-12

At first glance, the lens does not differ much in properties from Jupiter-12: BK is very sharp in the center of the frame with F / 2.8, but closer to the edges the resolution drops sharply and strongly due to pronounced coma. With F / 8-F / 11, the BK pleases with a sharp image and at the edges of the frame. But still, BK and Jupiter-12, when compared in detail, turn out to be different objectives in terms of optical properties.
Jupiter-12 and BK have a different coma observed over the image field. Below are illustrative paired examples.

Series 1:

photo on BC

Photo on Jupiter-12, F / 2.8.

Jupiter-12. F / 2.8

Photo on BC, F / 2.8.

Crop center and edge frames of series 1.

Crop center and edge frames of series 1.

Series 2:

photo on BC

Photo on Jupiter-12, F / 2.8.

Jupiter-12. F / 2.8

Photo on BC, F / 2.8.

photo on BC

Photo on Jupiter-12, F / 5.6.

Jupiter-12. F / 2.8

Photo on BC, F / 5.6.

Crop center and edge frames of series 1.

Crop center and edge frames of series 2.

As can be seen from the above examples, the Jupiter-12 coma is more pronounced, and its appearance is rougher than that of the BK. The different nature of the coma somewhat affects the bokeh of the lenses: the edging on the inner (closest to the center of the frame) side of the blur disk located at the edge of the frame is more pronounced in Jupiter-12, which indicates a worse correction.

Series 3:

photo on BC

Photo on Jupiter-12, F / 2.8.

Jupiter-12. F / 2.8

Photo on BC, F / 2.8.

Cropped bokeh around the edge of the frame.

Cropped bokeh around the edge of the frame.

The superiority of BK in resolution at the edge of the frame is well shown by the day test.

Series 4:

Left - photo on the BC, on the right - on Jupiter-12. The first row is F / 2.8, the second is F / 5.6, the third is F / 11.

Crop edge frames series 4.

Crop edge frames series 4.

Jupiter-12 noticeably loses in terms of resolution at the edge of the frame at apertures of F / 2.8-F / 5.6, it compares with BK only to F / 11. The above photos also clearly show the difference in color rendering of these two lenses: Jupiter-12 gives a colder picture.

Interestingly, BK and Jupiter-12 differ not only in the degree of coma correction, which could be attributed to poor assembly of a large-scale lens. The lenses also differ in geometry transmission: the BK has noticeably less pincushion distortion than Jupiter-12.

Overlay of two colored photos from BC (blue) and Jupiter-12 (red). F / 11.

Overlay of two colored photos from BC (blue) and Jupiter-12 (red). F / 11.

It also turned out that Jupiter-12 copes worse with backlight, despite the later antireflection coating.

Series 5:

photo on BC

Photo on Jupiter-12, F / 2.8.

Jupiter-12. F / 2.8

Photo on BC, F / 2.8.

Image overlaid from series 5 for contrast assessment.

Image overlaid from series 5 for contrast assessment.

Thus, the comparison shows the complete superiority of the BK over the serial Jupiter-12, which cannot be explained by the production defect of the latter. BK has more correct geometry, more sharpness at the edge of the frame and better contrast in backlight. However, it is possible that the "small series effect" also takes place: it is enough to remember that a rare early Industar-61L turned out to be much better than the later versions of the FED production.

I really like Jupiter-12, despite its inherent flaws. And I liked the BC, which possesses the best optical quality, even more - the old and rare lens has become a daily staff on my camera.

Below are examples of photos on Sony A7s (shooting in RAW, processing in Imaging Edge).

conclusions

Whether German glass was used by "Biogony Krasnogorsk" or Soviet - today it is difficult to know for certain. But the fact is that Zorky BK is significantly different optically from its large-scale descendant, and - unfortunately - the prototype once again turned out to be better than the mass. Anyway, BK is a very nice version of Jupiter-12 (or Carl Zeiss Jena Biogon?), Which will upset fans of this lens unless it is rare.

You will find more reviews from readers of Radozhiva here.

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Comments: 6, on the topic: Zorky BK 1: 2,8 F = 3.5cm P for Kiev cameras. Review from Rodion Eshmakov

  • UstasFritZZZ

    Thanks for the review, it was informative

  • Sergei

    The thing is purely collectible.
    In addition, this lens (like Jupiter-12), due to the large rear optical element, cannot be crammed into a cropped Sony mirrorless camera (and not only ...), which reduces its relevance.
    But, due to the availability of the Soviet version, incl. for the price, continues to hold interest for full-frame mirrorless cameras.

  • Neutron star

    "The first post-war lenses, made on German equipment and, possibly, glass taken out for reparations, with the help of German specialists ..."
    The glass had its own, like the designers! In the USSR, starting from the post-revolutionary years, the production of optical glass of the highest grades was established and the training of highly qualified personnel began. There is no need here "la-la, everything is stolen from the Germans."

    • Rodion Eshmakov

      In this case, not one's own and not one's own - a well-known fact. In general, Zenith himself does not deny this, what are you talking about?

      PS Your mail is very original indicated in order to leave a comment. Sounds like the truth, I agree.

    • Alexander

      not stolen, but taken as a very modest compensation. The fact that at first they used German glass is a well-known fact, which is confirmed by the people who established production at that time. Then the optical design was recalculated for other types of glass, and these were already different lenses.

    • Alexey

      but there was almost nothing of its own in the USSR. I speak as a person who worked at a large number of enterprises of the military-industrial complex of the USSR. the most accurate metal-working machines were just exported from Germany, and they worked at the enterprises of the military-industrial complex until the 90s, then they had to be disposed of, because they simply fell apart. and there is no need to talk about scraping everything electronic, now declassified resolutions of the Council of Ministers of the USSR and the Central Committee of the CPSU on copying Western electronic products have already been published, you can find and read. and we knew this even then, because we observed the very process of copying. ugh for all this, tired of typing.

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