Mirror-lens 5x lens of the night vision device "Cathode MNV", adapted for mirrorless cameras. Review from Rodion Eshmakov.

Material on this lens especially for Radozhiva prepared Rodion Eshmakov. I am sending this material for publication with a sincere desire to support the project of Arkady Shapoval in the current cruel time.

Lens after adaptation.

Lens after adaptation.

Recently, I have been studying the optics of night vision devices for civil and military purposes. In a previous article on the lens from a tank binocular TVNO-2B, the night vision device is shown and the features of "night" optics are noted, among which are high light transmission in the IR spectrum and aperture. Such requirements create significant difficulties in the design of long-focus lenses - in addition to correcting aberrations, it is also important to maintain acceptable weight and size parameters. The latter is not a trivial task, given how much the usual 85/1.2 - 200/2 lenses weigh. The conditional IR version of Sonnar 180/2.8 will not only be too “dark” for use in night vision devices, but will also turn a hand-held monocular into a stationary one. Engineers come to the aid of mirror-lens systems, which, in conditions of a small field of view angle and a small back vertex distance, make it possible to design lenses with perfectly incredible parameters.

Mirror-lens optics is a relatively developed direction in the Russian Federation, the basis of which is laid down by D.D. Maksutov in the USSR foundation. Serial night vision devices equipped with mirror-lens optics have been produced since the 1990s by factories in Krasnogorsk and Kazan. Known, for example, is the Zenit NV-500 monocular, equipped with 120 / 1.6 catadioptric lens. Similar lenses are used in binocular systemsincluding stereoscopic.

This article is dedicated to the 5x objective lens developed for the MNV and MNV-K night vision devices produced by Katod JSC. There is no marking on the lens, which makes it impossible to establish the manufacturer. Probably, the optics are produced by the Novosibirsk Instrument-Making Plant, since the head office of JSC "Katod" is located in Novosibirsk.

TECH SPECS [source]:

The optical scheme is a mirror-lens with Mangin mirrors, the number of components is unknown.
Focal length - 130 mm (determined experimentally);
Relative aperture - 1:2,3 (declared by the manufacturer - and already taking into account the central shielding), 1:1,8 (geometric);
Estimated field of view - 8 degrees;
Weight - 385 g;
Dimensions - 85x95 mm;
Features: IR lens. Does not have a variable aperture. A focusing mechanism suitable for photography is not provided by the design.

Design and adaptation

I got the lens completely assembled, even with the native focusing mechanism. But it was of no use, since it was a lens focuser of very small diameter and stroke, completely unacceptable for use with a camera. The focusing part is easily separated, exposing the main mirror, made like a Mangin mirror (sputtering is applied to the back of the glass lens - the element combines reflective and refractive functions). Below are photos of the lens block before adaptation.

The lens is made very roughly. There are traces of landing glue on the back side of the main mirror There is no matting of internal surfaces, and this, by the way, is often even more important for image contrast than enlightenment.

The lens is designed for a small field, but covers even a 36×24 mm frame. A significant disadvantage is the bright manifestation of parasitic frame exposure, which I have previously seen in Rubinar 500 / 8, but to a much lesser extent. The design defect lies in the possibility of light rays passing through the lens without being reflected in the mirrors to the photodetector (see photo of the lens block). This was done to reduce the size of the lens. When used as intended, a design defect will not manifest itself.

Adapting a lens block seems like a daunting task: a very large diameter and a small back focal length do not allow the use of any donor bodies, and metal parts would be cosmically expensive just because of the material alone. 3D printing technology came to the rescue in solving the problem. This was my first 7D modeling experience: a simple single-flute focuser, similar to the ones I had XNUMX years ago, was made for the rework glued of projector papers.

Models in STL format can be downloaded here.

Parts are made of polylactide (PLA). The focusing mechanism has a stroke of ~30 mm when rotated 270 degrees. The nose of the lens acts as the focus ring. The conical focuser cup is a necessity, not a design element. Without it, when attaching a lens to a camera, it would be impossible to put your fingers on its handle.

The operation of the focusing mechanism of the lens.

The operation of the focusing mechanism of the lens.

Such a design, of course, does not differ in convenience, smoothness, etc., but it is very simple and light.

From the pleasant - it was possible to implement a universal lens mount to the camera using the M39 thread, taken from the Industar-61 L / D body.

The M39 mount allows you to use the lens on any mirrorless camera. In the photo, an M39-NEX adapter is put on the shank.

The M39 mount allows you to use the lens on any mirrorless camera. In the photo, an M39-NEX adapter is put on the shank.

Below are more photos of the adapted lens.

As you can see, the lenses of the "Cathode" carry the same vigorous blue enlightenment that the lens had TVNO-2B 50/1.5 - This is a special coating for working in the IR range. I was not able to measure the transmission spectrum of the "Cathode" due to its special design and dimensions, but semi-quantitative measurements showed that it transmits blue rays about 10 times better than TVNO-2B, which is good.

Of course, the idea of ​​using such a specific lens requires one to put up with its serious shortcomings, but, I note: so far not a single manufacturer has provided a single reflex lens for cameras with a focal length <250 mm and aperture >F/4.5. In review Rubinar 4,5 / 300 I noted that short-focus mirror-lens optics would be very interesting for creative tasks because of their unusual picture - and the use of EVIL from night vision devices makes it possible to get this picture.

Optical properties

The lens is well corrected within the APS-C frame: the sharpness is very good, at the level of a good lens lens. Completely absent chromatic aberration, from which old lenses of the 135 / 2-2.8 class suffer greatly. At the edges of the full frame, the resolution is noticeably reduced, in this case field curvature and coma have the greatest influence. There is noticeable vignetting on full-frame cameras.

The contrast of the image is low, very low: the reason for this is the fatal stray illumination and the very poor quality of the blackening of the internal surfaces of the lens block. In the backlight, a strong veiling appears, crescent-shaped highlights are caught from point light sources.

Color rendition is specific, unnatural. This is due to enlightenment, which, on the one hand, does not transmit blue rays, on the other hand, it also gives a blue veil due to light reflections from the lenses. The resulting image simply does not have the correct white point. However, this unfortunate fact unties the hands of all color experimenters.

The lens has the craziest bokeh I've ever seen: here you can find bagels, and "eyes" (not just lemons, but right with the pupils - real ones!), And sickles. Don't get bored!

How simply the telephoto "Cathode" miserably loses to the old Carl Zeiss Sonnar 180 / 2.8 (currently I have nothing else to compare it to), and will lose to any more or less decent 135mm lens. But a "decent lens" will not give such an unusual picture, of course. Below is a comparison of the Cathode with the Sonnar 180 / 2.8, made on a Sony A7s camera. All shots were taken on an open aperture.

Of course, of course, Sonnar gives a much cleaner and easier-to-perceive picture without obvious flaws - photos from it do not need to be improved, while photos from the "Cathode" need to be "pulled out". But it seems that these shortcomings are that's… why I'm here ©.

Below are more examples of photos taken with the Sony A7s camera.

Conclusions

While Samyang, Tokina and LZOS are crumpled and shy, not risking releasing a short mirror-lens telephoto lens, extremely interesting lenses with “tasty” parameters and an unusual picture have long been produced for night devices. I am almost sure that the task of correcting the shortcomings of the "Cathode" is quite solvable while maintaining the properties. Even just changing the coating and adequate blackening would solve half the problems of the lens. But even in its original form, the lens makes a powerful impression, if not charm, with its picture, which is really “not like everyone else”. I repeat: this is the most unusual lens I have ever had.

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

Add a comment: Vlad

 

 

Comments: 13, on the topic: Mirror-lens 5x lens of the night vision device "Cathode MNV", adapted for mirrorless cameras. Review from Rodion Eshmakov.

  • Sergei

    The Novosibirsk Instrument-Making Plant (NPZ) produces and officially sells 8x ZLO for night vision devices. Front lens diameter - 123 mm, focal length 216 mm, geometric aperture 1,8 (real 2,3).
    Covers according to the declared field of view (5 °) Micro 4/3 (crop 1,5 is possible).
    But the weight is 1450 grams (!) And the price is 70-84 thousand rubles (!).
    Probably for non-market purchases, but it is officially sold on the refinery website.
    Also a surrogate focuser (from infinity to 10 meters).
    After a request to the factory, the answer came - a landing thread for connecting to the NVD M46 x 0,75, working length - 30,6 mm

    • Rodion

      This lens is equipped with PN-14K night vision devices.

  • Linnea

    Rodion Eshmakov, thank you very much!

  • German10

    Thank you, Rodion, for an interesting review!

  • Rodion Eshmakov

    Gentlemen, if anyone has any claims/questions/suggestions to me personally, please contact me personally, you have my contacts. I communicate with people from different countries of the world who want to ask me something or tell me something, including in the context of current events. Also, I have said more than once that I use different sources of information, including the remnants of Russian independent media and Ukrainian media.
    Radozhiva's materials are read by the whole world, site traffic serves as a source of income for its owner - everyone knows this. Publishing articles here for me is the best way to support Arkady. Refrain from posts written on emotions, at least here on Radozhiv. Even Arkady supported this approach:
    “UPDATE: Many have requested that comments be removed and closed on this post. If you have something to say - you can write to me in a personal.

  • Dmitriy

    One well-known in “narrow circles of limited people” video comes to mind, where there is such a dialogue:
    - Here they write on cigarette packs, “smoking kills”, maybe write this on vodka?
    – Why write “smoking kills” on vodka?
    This is me to the fact that everyone should do their own thing, the site should broadcast about photographic equipment and everything related to photography, and that's it, categorically.
    Then there will be order.

    • Vlad

      Unfortunately, the current situation is such that it is not possible to stay at a distance. De facto, it is in its purest form a struggle between good and evil. There have been no similar events since the Great Patriotic War. And you need to clearly understand who is to blame for this, to have and express your civil position. Tens of thousands of people have already died at the sick will of the bloody maniac. Staying away won't work. “I am for peace, stop the war” is also not a position.

    • Vlad

      And the glass on the move creates an interesting complementary color scheme.

  • Vlad

    At the same time, there are no complaints against Radion personally. Thank you for creating content during these difficult times.
    The lens is interesting. Bokeh seems to "vibrate". Probably, with this it will be interesting to shoot some kind of stylized fantasy. Although in general it is not easy to find a use for such

  • Anton

    Rodion, and in this “cruel time”, was it difficult to refrain from posting photos of the Kremlin as examples? And cheerful girls against the backdrop of its bell towers? Are these the only buildings that reveal the capabilities of the lens? Do you know the sense of tact?
    Here in Kharkov it is perceived differently.

    • Rodion

      Yes, it is difficult. After February 24, the girls in the photos already taken at the beginning of that month were unable to change their facial expressions. I didn’t want to specially redo the pictures so that the girls were sad, “in accordance with the spirit of the times”. There was no desire to invent other photographs either, and then the lens was sold quite quickly at all. In general, for the whole month of March, I didn’t have much desire to do something, however, in order to support the site (and its monetization), a dozen of my reviews and articles were published in less than 4 months. What tact are you talking about? I'm busy with something specific.

      • B. R. P.

        Rodion, do not pay attention. Do what you did. You definitely have nothing to justify.

        • Victor

          +1

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