Uran-27 1:2,5 F=10cm (KOMZ) is an aerial photography lens adapted for use with modern cameras. Review from Rodion Eshmakov

Material on this lens especially for Radozhiva prepared Rodion Eshmakov.

Adapted lens Uran-27.

Adapted lens Uran-27.


Uran-27 100 / 2.5 - a representative of Soviet aerial photography lenses, used with the AFA-39 camera mounted on reconnaissance aircraft. It was produced in a large series at KOMZ (Kazan) and, along with Telemar-17 400 / 6.3 and F-3 400 / 4.5, is one of the most common aerial photographic lenses. Thanks to a rather outstanding picture and attractive parameters, it has earned a certain demand as an unusual portrait lens.

Uran-27 lenses of different years of production differ greatly from each other in the type of enlightenment: there are lenses with amber, pink and purple lens coatings.

Optical coating has a decisive influence on the color reproduction of the lens and its behavior in backlight, because lenses that are strikingly different in enlightenment are, one might say, completely different lenses. Most often you can find late versions of the lens with bright blue enlightenment, produced in the 60s. An overview of such a modification of 1969 release already on Radozhiv. And this article presents a 27 Uran-100 2.5 / 1960 lens adapted for modern cameras with a violet lens coating.

Specifications:

Optical design - 7 lenses in 5 groups ("Uranus", a variation of the "Planar" scheme);

Lens card in the GOI catalog.

Lens card in the GOI catalog.

Focal length - 100 mm;
Relative aperture - 1: 2.5;
Aperture - 12 rounded petals;
Aperture limits - 1:2.5–1:16.
Field of view angle (in 8×8 cm format) – 61°;
The back focal segment is 65 mm;
Weight (without flange) - 1 kg;
Features - does not have its own focusing mechanism, mounts for modern cameras.

The history of the development and development of lenses "Uranus"

Semi-lens lenses of the Uranus family (the god of Heaven in Greek mythology) are an original development of Soviet optics David Samuilovich Volosov, author of numerous scientific articles, patents, books, also known for the development of optical schemes for lenses "Tair","Telemar","Era».

Portrait of D.S. Volosov.

Portrait of D.S. Volosov.

In the 1944 patent (!) SU68727A1 a schematic diagram of a small-format wide-angle (angle of view 63°) lens with parameters 35/2 is described, which, however, was never produced. The key element and hallmark of this optical design is the presence of a meniscus corrector just after the aperture in the rear lens block of the lens. This element contributes to the fight against field aberrations like the meniscus in the Tahir lenses. The “visiting card” of the lenses is also a huge rear lens in diameter - it is usually larger than the front lens, which is done to ensure a wide field of view of the lens.

The optical design of the Uranus 35/2 lens, given in the patent by D.S. Volosov.

The optical design of the Uranus 35/2 lens, given in the patent by D.S. Volosov.

Lenses "Uranus" are designed for a meager palette of optical glass of the USSR of the 40s, in which the "last word of technology" was the usual heavy TK crowns and BF barite flints. This circumstance, however, did not prevent David Samuilovich from dreaming already in the 1940s of switching to lanthanum glasses, which would have made it possible to achieve F / 2 aperture with a wide-angle seven-lens optical scheme.

Abbe diagram for a modern catalog of optical glass produced by LZOS. Red marks the glass grades that are most often melted. Glasses TK and BF are the middle of the diagram.

Abbe diagram for a modern catalog of optical glass produced by LZOS. Red marks the glass grades that are most often melted. Glasses TK and BF are the middle of the diagram.

A number of aerial photographic lenses Uranus are known: Uran-10 100/2.5 (1943), Uran-27 100/2.5 (1951), Uran-9 250/2.5, Uran-25 200/2.5. There was also a completely monstrous projection Uran-12 500 / 2.5 (aperture 200 mm!) And not mass-produced prototypes of wide-angle lenses for rangefinder cameras Uran-14 35 / 2.5 (based on Uran-10) and Uran-26 35 / 2.5 (related to Uranus -27).

The most common lenses are Uran-27 and Uran-10, which have the same parameters, but are made of different types of glass and generally differ in correction: the newer Uran-27 has a higher resolution when shooting in the full visible spectrum than Uran-10, which to achieve good image quality, it was recommended to use with an orange filter.

Uran-10 lens card in the GOI catalog.

Uran-10 lens card in the GOI catalog.

Much less obvious is that the Uranus optical design itself is far from being found only in Uranus lenses. For example, a rather rare OKS1-35-1 film lens is made according to this scheme and has aperture F / 2, but at the same time its angle of view is limited to 46 °. In the GOI catalog, this lens is called "Uran-20" (1945). "Uranus" is also a "mythical" film projection lens for 70 mm film OKP2-110-1 110/2.

It is surprising that Volosov's scheme was also successful abroad: lenses for rangefinder cameras Summicron 35/2 (version 4) and Planar 35/2 Contax G are classic "Uranus". What did not materialize under Volosov in the USSR, the Germans were able to do decades later.

Lenses "Uranus" are not always called that way.

Lenses "Uranus" are not always called that way.

And this is not the first example when the achievements of domestic opticians become the basis for recognizable foreign products. So, for example, Russar lenses became the prototype of L. Bertele's symmetrical wide-angle Biogon lenses (read the history of lenses "Russar" is here).

As of today, none of the manufacturers produces lenses with the Uranus optical design: the same Leica and Zeiss replaced it with sophisticated modern designs that provide the best image quality, but the Chinese have not reached and are unlikely to get there (although that something vaguely reminiscent they had). It is strange that these lenses were completely forgotten in their homeland: when developing a lens at KMZ Zenitar 35/2 instead of the well-documented wide-angle Uranus seven-lens scheme, they used a scheme of a typical old 50 / 1.4 lens, obviously with a very mediocre result.

Design and adaptation of Uran-27

The heavy body of the lens has a non-removable massive metal flange for camera mounts, which must be cut for adaptation. Alteration of the lens is both simple and complex: since the diaphragm is already there, and the rear segment is large enough, there is no fundamental difficulty, but the lens has a very large body diameter (more than 70 mm) and it is extremely difficult to choose a helicoid for it.

You can find numerous modifications of the Uran-27 lens with small-diameter focusers mounted behind the lens block, but such products suffer from a number of disadvantages: 1) congestion of the helicoid, low reliability of the focuser and its uncomfortable movement, 2) strong shielding of the rear lens in some cases, 3) poor mass balance and unsatisfactory ergonomics, 4) loss of compatibility with SLR cameras and shift adapters. This is important to consider when planning work on the lens.

To adapt my lens block, a custom-made focusing mechanism with multi-thread threads was made, which provides smooth and convenient focusing. For the convenience of focusing, a wide ring is made on the nose of the lens, which also carries a thread for 77 mm filters. The M42 thread was chosen as the fastener. Despite the small light diameter of the mount, vignetting is negligible even on 44x33 format cameras. When replacing the mount with an EF mount, vignetting can be completely eliminated with shift adapters and medium format cameras, since the lens itself works with the 8x8 cm format.
Photos of the adapted lens are shown below.

It can be noted that the version of Uran-27 with violet coating of optics distorts the transmission spectrum to a much lesser extent than the version with blue lens coating.

The medium-format-wide-angle nature of the Uran-27 lens leads to the fact that its dimensions and weight turn out to be colossal for class 100 / 2.8 optics: it is 3 times heavier and ~ 2 times larger than a wonderful projection lens Belar-2 90/2.5 or brighter LZOS MS Rubinar 2/100. Nevertheless, it still remains quite convenient and easy to handle with proper adaptation.

Optical properties

The Uran-27 lens on small-format cameras forms a very good quality image already from an open aperture. The sharpness of the lens in the central region of the frame differs little from the sharpness of lenses such as Belar-2 90/2.5 и MC Rubinar 2 / 100, which I have on hand at the time of this writing. In some cases, when using a lens, you can observe a slight spherochromatism. Sharpness across the field of the frame is limited mainly by a small coma and is at the level of Belar-2, significantly ahead of the five-lens Rubinar 2/100 at an equal aperture. As you can see from the tricky dependence of the lens resolution on the angle of view, Uran-27 is corrected by playing with the mutual compensation of 3rd and 5th orders of aberrations, resulting in a resolution peak at the edge of the lens field, which will be unattainable on modern cameras.

The lens presented in the review was examined by LZOS specialists to obtain data on the modulation transfer coefficient (that is, the frequency-contrast response) of the lens, shown in the figure below. It can be noted that by modern standards, the MTF lens on the optical axis looks very modest. However, Uran-27 turns out to be much better than, for example, a lens Jupiter-9 85/2 manufactured by KMZ, which is not considered a bad lens at all. It's funny that a completely primitive lens KO-120 120/2.1 significantly ahead of Uranus-27 in terms of the MTF value for the image on the optical axis.

Frequency-contrast response of Uran-27 measured at LZOS without filter and with green-blue filter ZS-1.

Frequency-contrast response of Uran-27 measured at LZOS without filter and with green-blue filter ZS-1.

When apertured down to F / 3.5-F / 6.3, the Uran-27 behaves like a completely excellent lens in the field of a small format frame.

The most significant nuances when working with a lens are contrast and color reproduction. Due to the large working field, the “extra” light rays in a small format are re-reflected from the structural elements of the focusing mechanism and large objective lenses, which leads to the appearance of a veil of color corresponding to the color of the lens enlightenment. In this case, it is a purple haze that lowers the contrast in the backlight and distorts the color. Further, since the violet coating blocks the transmission of violet light rays, the lens itself noticeably turns yellow-green. Auto white balance is able to overcome only the effect of distorted light transmission, which prevails when using the lens in normal lighting conditions. A veil is added in the backlight, white balance loses its meaning and turns into a creative tool - nothing more. A deep hood and high-quality blackening of the behind-the-lens space allows you to effectively deal with veiling.

Uran-27 is one of the most "difficult" lenses to work with color along with 16KP-1,4 / 65 и TVNO-2B 50/1.5.

Uran-27 is the owner of a very peculiar "oily" bokeh, which, due to the combination of various factors, is not characteristic of more "simple" lenses.
Below are sample photos taken with the Sony A7s full-frame camera.

The large coverage area allows the lens to be effectively used on 44x33 format cameras and with shift adapters for taking panoramic photographs. I used the Fotodiox EOS-NEX adapter on a Sony A7s camera to take 36×45mm (4:5) and 24×56mm (2.33:1) format photos, sample photos are shown below.

Conclusions

For me, shooting with a Uran-27 lens (both this and "blue") is, first of all, a fascinating process in which it is difficult to predict the result for sure. A multifaceted play with light, bokeh that manifests itself in different situations, a large working field - all this opens up a lot of opportunities for getting interesting shots with this lens. The psychological factor plays an important role in the pleasure received when shooting: large beautiful convex lenses, a bright sheen of enlightenment, impressive weight and an interesting story create a certain special attitude to the process. Yes, just love it. Of course, there are many more affordable, convenient, predictable and high-quality optics of classes 100 / 2.8 and 100/2, but for some reason, not only collectors feed interest in old aerial photography "uraniums"?

You will find more reviews from readers of Radozhiva here... All Rodion reviews in one place here.

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Comments: 5, on the topic: Uran-27 1:2,5 F=10cm (KOMZ) is an aerial photography lens adapted for use with modern cameras. Review from Rodion Eshmakov

  • Alexander Rifeev

    well - the old 10,67 mm Smith-Wesson Russian revolver, when shooting at close range, even brought down a bull from the very first shot :-))) and a 7,62 mm Nagant brought down a horse :-))) ... but if Nagant can still be found , then Smith-Wesson is Russian - hardly :-))

    • B. R. P.

      They were not made against horses and bulls.

  • Sergei

    There is a reason to remake it only for 44x33 mm format (like Fujifilm GFX) or 54x41 mm digital backs.

    • Rodion Eshmakov

      In my version, it just easily copes with 44x33, but 54x41 will probably already have vignetting due to the mounting thread.

  • mr.swar

    “It is surprising that Volosov's scheme was also successful abroad: lenses for rangefinder cameras Summicron 35/2 (version 4) and Planar 35/2 Contax G are classic "Uranus". What was not embodied under Volosov in the USSR, the Germans were able to do decades later.”
    In the 50s-60s, all manufacturers had almost identical optical circuits, the limitations of patents in civilized countries. Germany did not infringe patents, lawsuits could sink the company. The calculation of optics was painstaking at that time and was considered hard work, out of 10 opticians, 1-2 calculators were normal. Computers at that time did not draw beams, so everything was done by hand. The maximum that computers could do was to optimize aberrations, Volosov's book is very well described. Now everything is different, every decade a small breakthrough.

    “As of today, none of the manufacturers produces lenses with the Uranus optical design: the same Leica and Zeiss replaced it with sophisticated modern designs that provide better image quality, but the Chinese have not reached and are unlikely to get there (although something remotely resembling them). It is strange that these lenses were completely forgotten in their homeland: when developing the Zenitar 35/2 lens at KMZ, instead of the well-documented wide-angle Uranus seven-lens scheme, they used the scheme of a typical old 50 / 1.4 lens, obviously with very mediocre results.”
    The Chinese copy what is hyped on the Internet. You can write to the Chinese and promote Uranus, in a couple of years you might get a UranChina lens.

    “As you can see from the tricky dependence of the lens resolution on the angle of view, the Uran-27 is corrected by playing with 3rd and 5th order mutual compensation of aberrations, resulting in a resolution peak at the edge of the lens field, which would be unattainable on modern cameras.”
    There is nothing surprising. This technique was practiced by Japanese calculators. It is better to remove the real resolution by three points at all apertures. LZOS people know how to do it. Then we will discuss the measurement results. Ask the LZOS people to measure the residual sphere of your specimen.

    “The lens presented in the review was examined by LZOS specialists to obtain data on the modulation transfer coefficient (that is, the frequency-contrast response) of the lens, shown in the figure below. It can be noted that by modern standards, the MTF lens on the optical axis looks very modest.”
    Naturally. At the very beginning, this was said, the patent confirms this. Films with a resolution of 200-300 lines / mm were not intended for this lens. See my request above.

    “Further, since the violet coating blocks the transmission of violet light rays, the lens itself is noticeably yellow-green.”
    Violet enlightenment is a reflex. To talk 100% about enlightenment, look for a technological map for applying enlightenment to this lens. It's very easy to find if you have connections. For good, you need to have another one of the same lens in order to chemically remove enlightenment and then you will find out the real shade of the lens itself and the glasses, but this is already aerobatics.

    PS For the review and the time spent, personal thanks.

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