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
Characteristics of Uranus-27
Optical design: 7 elements in 5 groups, “Uranus” (a variation of Planar)
Resolution (for the format 8 * 8 cm, on the Isopanchrome film type 22 - according to photohistory.ru) center / edge: 44/8 lines / mm;
The field of view angle in the native format (8 * 8 cm): 54 degrees;
Aperture Limits: F / 2.5-F / 16;
Diaphragm design: twelve-petalled, rounded, non-black, without presetting mechanism and ratchet;
Thread diameter for filters: no, smooth nozzles 76 mm;
Mount: cast flange mount to the aerial camera;
Focuser: none;
Features: applicable to all visible light, orthoscopic.
Uranus-27 is an infrequent technical lens that was used for aerial photography with AFA-39 cameras. Apparently, it was produced at the Kazan OMZ, judging by the nameplates of the early lenses.
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 fixed flange, complicate the adaptation. But Uranus-27 has a fairly large back segment, which allows you to put it on any small format TsZK. But for medium-format DSLRs, the segment may not be enough.
My lens had oil condensate inside (it came from the diaphragm for many 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 simply monumental, foolproof design - each retaining ring is fitted with 1-3 retaining screws; each part is thick, durable and metal, the lens units have their numbers and are planted in accordance with the risks involved. It immediately feels that the lens is assembled extremely high quality.
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 - a frame of 8 * 8 cm, it has enough resolution even on a modern digital camera (on which we use only the center of the coating spot). This means that we have a stable 44 lines / mm throughout the frame.
An open diaphragm can be safely called a working diaphragm.
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
Uranus-27 uses the old palette of optical glasses and the old type of enlightenment - single-layer, "blue". Due to this, he is very yellow in lumen:
Uranus-27 (Uranus-27) 2.5 / 100
It seems to me that this is the main drawback of the lens, because blue enlightenment not only distorts colors (leads to the green-yellow area), but also brings its reflections and blue flare. As a result, it is very difficult to correct a picture distorted by a blue veil and an excess of yellow light. By the way, the flare lens does not digest - the slightest back-up plunges it into the "blue abyss".
Veil with the black back of the focuser
However, this is solved by high-quality blackening of the back of the focuser and, of course, an 8-centimeter hood (which is planned to be made). In addition, you can apply a pink Sky-Light filter to reduce the effect of green light on the picture - as a result, the lens will simply warm up to ~ 500K picture, but no more.
Of the aberrations, chromatism affects the image most of all - it often manifests itself in contrasting details on the open diaphragm. Spherical aberrations are quite small.
With aperture already at stop-stop, the sharpness becomes very, very high.
Uranus-27 has, in my opinion, a very nice picture - it has excellent bokeh, good sharpness. Even distorted color reproduction on a sunny day is appropriate, giving the picture an interesting effect.
Conclusions
Uranus-27 is a very unusual lens - aerial photography. Despite its purely technical purpose, it has high optical performance and an excellent picture. The main disadvantage of the lens is a poor enlightenment, which is offset by high-quality blackening and the use of a lens hood. Despite the difficulties of adaptation, the lens fully justifies the expended forces. I recommend.
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.