View of the lens Uranus-27 2.5 / 100 and examples of photographs from it, especially for Radozhiva, prepared Rodion Eshmakov.
Uranus-27 (Uranus-27) 2.5 / 100
The Uran-27 is a rare technical lens used for aerial photography with AFA-39 type cameras. It was apparently manufactured at the Kazan OMZ, judging by the emblems on the title rings of other known lenses. A newer review of another version of the Uran-27 lens (with pink-violet optics coating) and historical information here.
Characteristics of Uranus-27
Optical design - 7 lenses in 5 groups ("Uranus", a variation of the "Planar" scheme);
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.
Design and key features of the adaptation of Uranus-27
Uranus-27 is a massive metal lens block with a diaphragm with a large cast flange mounting an unusual shape.
The indecent dimensions of the lens, especially its non-removable flange, complicate adaptation. But the Uran-27 has a fairly large rear segment, which allows it to be mounted on any small-format CZK. But for medium-format SLRs, the segment is not enough.
My lens had oil condensation inside (it got there from the diaphragm during long years of storage), which required complete disassembly and cleaning. It is worth noting here that, like any product of the Soviet military-industrial complex, this lens has a monumental foolproof design - each locking ring is mounted on 1 or 3 locking screws; each part is thick, strong and metal, the lens blocks have their own numbers and are mounted in accordance with the marks applied. It is immediately felt that the lens is assembled extremely well.
After service, the adaptation was carried out:
- Dremel sawed the mounting flange neatly - we do not need it. Again, I take off my hat to the engineers - there is as much metal in this metal flange as there are in a dozen G-44-2s.
- A threaded focuser was ordered taking into account the large weight of the lens. The focuser consists of two glasses - on the internal thread turn (like a screw, with a pitch of 36 mm, 1 mm high and 2 mm wide) and another turn of a similar thread (groove), only in the manner of a "nut" (depth and other parameters same) - for the stock. The outer glass - the counterpart ("nut") to the internal thread, has a bottom with M42 thread for attachment to the camera.
- Details were ground, painted, assembled. The lens Uranus-27 was fixed in the inner glass.
In the end, we got such a heavy barrel, which can be hooked onto any modern small-format camera:
Uranus-27 (Uranus-27) 2.5 / 100
Uranus-27 (Uranus-27) 2.5 / 100
Optical properties of the lens Uranus-27
Despite the fact that the lens is designed for medium format - 8*8 cm frame, its resolution is sufficient even on modern crop cameras, where only the center of the covered image is used. This means that the drop in image quality from the center to the edge on a small format can be expected to be quite small.
The open aperture can be confidently called working: the lens forms a sharp image without significant flaws. Of the aberrations, residual chromatic aberration has the greatest impact on the image - it appears on the contrast borders at the open aperture. Spherical aberrations are quite small. With the aperture already at one stop, the sharpness becomes very high.
Uranus-27 (Uranus-27) 2.5 / 100
By the way, about the diaphragm - at Uranus-27 it is beautiful, large and even:
Uranus-27 (Uranus-27) 2.5 / 100
Uran-27 uses an old type of enlightenment - chemical (probably spin-coating SiO2) single-layer, "blue". Due to this, when held up to the light, it turns very yellow.
Uranus-27 (Uranus-27) 2.5 / 100
Indeed, the maximum light transmission of the lens is not in the green (~540 nm), but in the red (~630 nm) region of the spectrum, while the blue region is strongly truncated (by 50-70%).
Light transmission spectrum of the Uran-27 lens.
It seems to me that the wrong transmission spectrum is the main drawback of the lens, because the blue coating not only distorts colors (leads to the green-yellow region), but also introduces its own reflections and blue glare. As a result, it is very difficult to correct a picture distorted by a blue veil and excess yellow light. By the way, the lens does not like flare - the slightest backlight plunges it into the "blue abyss".
Veil with the black back of the focuser
The problem of fogging can be partially solved by high-quality blackening of the back of the focuser and, of course, a long hood.
Overall, Uran-27 has, in my opinion, a very nice picture - it has excellent bokeh, good sharpness. Moreover, even distorted color rendition can be appropriate, giving the photo an extremely interesting effect, which is difficult to achieve specifically when editing photos.
Update: Uran-27 and Fujifilm GFX 44×33 mm, infrared shooting
Additional information on the use of the Uran-27 lens on the medium format Fujifilm GFX 50R camera, as well as in infrared photography, was provided by Alexander Korolev. The lens for it was specially adapted by me taking into account current experiencePhotos of the lens used are shown below.
The text below contains Alexander’s personal impressions.
For daylight shooting, the lens delivers excellent results in terms of sharpness, pattern, and frame coverage. For shooting waist-length portraits on GFX-type cameras, the lens delivers a good combination of focal length and aperture. Color rendition and contrast are easily corrected in post or even by using profiles built into the camera and adjusting white balance on the sheet.
When shooting people indoors under artificial light, the lens becomes extremely capricious in use. Color correction in mixed light (windows and lamps) is difficult to implement, when correcting the skin tone, the shadows turn blue. Light sources indoors give parasitic bluish glare in the frame. This can be used to create futuristic effects in a portrait, but more often it will turn out to be a technical defect.
The lens reveals itself perfectly in infrared photography with an 830 or 850 nm filter - there are no extraneous flares ("hotspots") at any aperture value, the contrast and sharpness do not drop in the IR spectrum, the lens coating allows avoiding parasitic flares from radiation sources (note from the author of the review - the lens coating really corresponds better to the near IR region than to the visible range).
The significant size and weight of the modified lens make it more reasonable to choose Fujifilm GFX 50s/50s II/100s cameras with a front grip for its use. For the Fujifilm GFX 50R with its “rangefinder” layout of control elements, the lens is on the verge of comfortable use. Nevertheless, its dimensions and weight on the camera create a confident vibe of working with a classic “Texas Leica” - Fujica G690.
Sample photos taken with the Fujifilm GFX 50R in the visible spectrum are shown below.
Next are the pictures taken with Fujifilm GFX 50R in the infrared range with an 830 nm filter (cutting off the range below 830 nm). The IR filter of the camera matrix was removed.
Conclusions
The “Blue” Uranus-27 is a very unusual lens. Despite its purely technical purpose, it has high optical performance and a pleasant, memorable picture. The main drawback of the lens is the ambiguous lens coating, which leads to strong color distortions in photographs, which in some situations look very interesting and cool, but no less rarely spoil the frame. In general, despite the complexity and relative high cost of high-quality adaptation, the lens fully justifies the effort expended.
You will find more reviews from readers of Radozhiva here.
I use Uran-27 on a Fujifilm GFX 50R.
The adaptation is very simple and technologically advanced: the master removes excess metal from the lens block on the machine and grinds 2 smooth nozzles that are fixed on the body with tugs - the front one with a thread for a light filter and the rear one with a thread for a helicoid. The M65-GFX adapter is screwed onto the helicoid at the back. Et voilas!
This is how it looks after adaptation:
Cool. Really voila.
The helicoid is only overloaded, as the lens hangs on the large shoulder.
Eh, no matter how good such lenses are, their reviews are still better!