Demilitarization: 50mm f/1.5, TVNO-2B tank night vision lens adapted for mirrorless cameras. Review from Rodion Eshmakov

Material on this lens especially for Radozhiva prepared Rodion Eshmakov (subscribe to Instagram!).

From human armored cans - straight to the camera!

From human armored cans - straight to the camera! increase.

This article is dedicated to an unusual 50/1.5 lens that was never intended for photography - the lens from the TVNO-2B night vision binocular, which was installed in Soviet military equipment, in particular, in the T-62, T-64 tanks, etc. The lens has no name, it is not even designed to work in visible light. Manufacturer - Izyum Instrument Making Plant, famous for its remarkable film projection lenses 16KP и 35KP.

I have adapted both of the removed lenses for use with modern mirrorless cameras. For me, this is not the first experience of “forging plowshares from swords” - read also an article about an interesting Tair-62T 95 / 2.5 from the bomb guidance head.

Lens specifications:

Optical design - 5 lenses in 3 groups, "Sonnar" (similar to CZJ Sonnar 180 / 2.8);

Principal optical scheme of the TVNO-2B NVG lens.

Principal optical scheme of the TVNO-2B NVG lens.

Focal length - 50 mm;
Aperture ratio - 1: 1,5;
Field of view angle — 30° (corresponds to ~APS-C frame);
Experimental light transmission coefficients - 0,59 (380-800 nm), 0,60 (400-780 nm), 0,90 (800-1100 nm);
Features - a lens for the infrared range, does not have a focusing mechanism and a variable aperture.

Night vision devices: varieties, principle of operation and optics

Sources: 1, 2, 3.

The military-industrial complex often serves as one of the main consumers of the benefits of scientific and technological progress. To facilitate the conduct of war in conditions of insufficient lighting, the first night vision devices (NVD) were developed during WWII, using infrared (IR) radiation invisible to the human eye. The principle of operation of a night vision device is based on the phenomena of the photoelectric effect and electroluminescence: 1) the lens builds an image of the object of observation in IR rays on a photocathode made of a material with red border in a longer wavelength region than the light used; 2) the photocathode emits electrons knocked out by infrared radiation quanta, which are directed by an electric field in vacuum to a luminescent screen; 3) when an electron collides with the screen, a flash occurs with the emission of visible green radiation - thus, an image in the visible range is obtained from an image in IR rays; 4) the image from the screen is observed with the help of an eyepiece.

Schematic diagram of a night vision device.

Schematic diagram of a night vision device.

A photocathode, a vacuum housing, an electronic lens, and a luminescent screen make up a single electrovacuum device called an image intensifier tube (IOC). Devices so-called. "zero generation", based on this simplest scheme, can work effectively only with external illumination of the object with infrared radiation invisible to the eye and were used by the Nazi troops during night battles. Devices of the 1st generation use a similar scheme, but differ in a new photocathode material (cesium-oxygen-silver, sodium-potassium-cesium-antimony), which provides a better quantum yield, and therefore can also work in a passive mode. It is the 1st generation night vision devices that are now the most common and affordable.

Further modernization led to the emergence of cascade image intensifier tubes, in which the 1st generation image intensifier tube is combined with photomultiplier. To increase the resolution of devices and reduce the influence of spurious illumination, "pixel" image intensifier tubes based on microchannel optics were invented. Advances in the study of inorganic materials have made it possible to raise the quantum yield and expand the spectral sensitivity of photocathodes—this is how the second and subsequent generations of devices appeared.

However, not only the image intensifier tube determines the efficiency of the night vision device - the lens used plays an important role: the total number of photons falling on the photocathode of the image tube depends on it. This makes it especially important to achieve maximum lens aperture. At the same time, night vision devices usually operate in a narrow spectral range (~800-1000 nm), which makes it possible to think less about the correction of chromatic aberrations. You can also sacrifice light transmission in the visible range in favor of IR by applying a special anti-reflective coating to the lenses. Further, the device must be compact: and for this reason, optics with a small back vertex distance are often used.

Not all night vision lenses, however, meet all of the above characteristics: for example, ROMZ Cyclops 85 / 1.5 from the NZT-1 tube and the optics of the PNV-57 night vision goggles do not have special enlightenment for working in IR. But optimization, as a rule, takes its toll: in the 1s, the same NZT-2000 tube began to be equipped with a new lightweight four-lens (a kind of Tair scheme) lens 85/1.5 with extremely low trailing edge and IR coating. In the early Soviet military devices, at first non-specialized lenses were probably also used: for example, in the optical scheme of the TVN-1, the outlines of the lens are clearly traced, which is very reminiscent of Jupiter-3 50/1.5.

Device TVN-1 and its optical design.

Device TVN-1 and its optical design.

However, even in the 50s, a line of lenses was designed specifically for military use: 150 / 1.5 Helios-52 (sight TPN-1), 100/1.5 Helios-50 (commander's device TKN-1) and the hero of this review is a little-known nameless 50 / 1.5 (devices of the driver-gunner TVN-2, BVN-2). All of the listed lenses are unsuitable for operation in the visible range, at least due to the applied coating.

Modification of the TVNO-2B lens to work with modern mirrorless cameras

TVN-2 and its modifications (in particular, TVNO-2B) use image intensifier tubes VEI-3 with Ag-O-Cs cathode. The size of the photocathode is much smaller than, for example, a standard film frame. We can say that this is a crop image intensifier tube xD. I wonder what needs to be torn apart in order to get the image intensifier tube "full frame" O_o ...

Device driver-gunner TVN-2 and its optical design.

Device driver-gunner TVN-2 and its optical design.

One way or another, due to this feature of the photodetector, lenses (with the exception of the well-known Helios-50 and 52) perform under a small frame, approximately corresponding to APS-C. Although there were mentions of a modification of the 50 / 1.5 lens, which has an enlarged rear lens and works with a full frame.

Due to the limited field 50 / 1.5, the TVNO-2B lens is made according to a rather simple five-lens Sonnar scheme, and not according to the seven-lens one, like Jupiter-3, which has a larger field with the same parameters. Interestingly, I have already come across a technical lens for the IR region, made according to such a scheme - this is the research Pentacon 125 / 2.8 https://radojuva.com/2021/08/2-8-125mm-pentacon-lens/ . Actually, the positive experience of using it prompted me to continue researching IR-Zonnars.

The procedure for adapting TVNO-2B lenses included two stages: installing the iris diaphragm and placing the lens block in the focusing mechanism. There are few reserves in the lens block, it is not easy to select and install the diaphragm - turning work is required. I did not measure the original size of the pupil of the lens, but before setting the aperture, it was smaller - that is, during adaptation aperture increased to the nominal 1:1,5, determined by the size of the entrance pupil of the lens.

Lens blocks of TVNO-2B 50 / 1.5 lenses with a fixed aperture.

Lens blocks of TVNO-2B 50 / 1.5 lenses with a fixed aperture.

Lens blocks of TVNO-2B 50 / 1.5 lenses with a fixed aperture.

Lens blocks of TVNO-2B 50 / 1.5 lenses with a fixed aperture.

In fact, as it turned out later, the position of the aperture is not quite ideal - in addition to limiting the pupil, it also introduces a slight vignetting during operation. However, without knowing the parameters of the optical scheme, it is unlikely to be better done.

After installing the diaphragm, adapters were ordered and made, allowing you to install lens blocks in factory-made macrohelicoids with an M42 thread. In this case, the aperture is controlled by turning the lens block.

TVNO-2B lens redesigned for Sony cameras.

TVNO-2B lens redesigned for Sony cameras.

The rear segment of the lens is very small - the lens is in the bayonet plane. The ratio of the rear segment to the focal length is much less than even the rangefinder Jupiter-3.

View of the rear lens of the TVNO-2B lens adapted for Sony.

View of the rear lens of the TVNO-2B lens adapted for Sony.

View of the closed aperture of the TVNO-2B lens.

View of the closed aperture of the TVNO-2B lens.

All objective lenses are bright blue AR coated for best performance in the IR range. The lens is just orange through the lens.

Bright blue reflection of the front lens.

Bright blue reflection of the front lens.

Looking through the lens - you can see a very strong distortion of the transmission spectrum.

Looking through the lens - you can see a very strong distortion of the transmission spectrum.

It cannot be said that the lens from the TVNO-2B device is easy to adapt: ​​if the selection of the helicoid is really not difficult, then the choice and installation of the aperture, and the removal of its control are rather difficult. However, the rebuild doesn't require building a lens case from scratch, which is great.

Optical properties

As noted earlier, the TVNO-2B lens can only work with APS-C and smaller matrices. At an open aperture, the lens gives a very soft picture with a pronounced glow of the contours, even in the center of the frame. Sharpness decreases significantly towards the edge due to the influence of field aberrations. When aperture is already at 1/2 - 1 stop, the optical quality returns to normal and the lens shows very good sharpness in the center. But in the corners of an APS-C frame, resolution generally remains weak. Chromatic aberrations hardly noticeable, appearing only as an orange-blue fringing in the nearest defocus zone (spherochromatism) - I expected much worse. At an open aperture, vignetting is very slight, it increases slightly with aperture due to the non-optimal aperture position.

The pattern and bokeh of the lens are very unusual. Previously photo posted on social media, in which it was necessary to guess the optical scheme and the year of production of the lens from the given black and white photos. Many assumptions were made, among which were indications of lenses with the "Zonnar" scheme, and Radozhiva's readers also noted the "imbalance" of the lens, as if it was poorly calculated for some reason. All this is true, only the lens is not poorly designed, but is designed for a different radiation. TVNO-2B optics have a really very peculiar bokeh, which changes greatly with aperture. Photos taken with the lens in b/w have a good vintage feel to it.

Image contrast is not high, it improves somewhat with aperture. However, the lenses strongly scatter light (especially blue), resulting in a characteristic veil or spot in the center of the frame. Even some photographic optics suffer from such a disadvantage, for example, the “blue-eyed” Helios-44 of the early 60s (series 00 ...).

The light transmission of the TVNO-2B lens was studied by spectrophotometry. The light transmission coefficients of the lens for different wavelength ranges were also determined: 0,59 (380-800 nm), 0,60 (400-780 nm) - different estimates of the boundaries of the visible region, 0,90 (800-1100 nm) - near IR range . It turned out that the shape of the spectrum is very different from the typical transmission spectrum of a single-coated lens for working in visible area: there is no pronounced peak, but in the near infrared region, even and high light transmission is provided - about twice as high as that of conventional optics. The lens cuts blue light almost completely, which will have a huge impact on color reproduction when used in the visible range.

Transmission spectrum of the TVNO-2B lens.

Transmission spectrum of the TVNO-2B lens.

In general, the work of the lens coating in the visible range can be described as a "warming" frequency filter with a linear profile. It is important to understand, however, that the spectrum does not take into account the effect of light scattering from glass-air surfaces on photography, which plays a large role when used in complex lighting.

When working with this lens, it is impossible to accurately and surely predict the result - it is too unlike ordinary optics. Nevertheless, it seemed to me that TVNO-2B optics have a very great potential in black and white photography, as well as when photographing in difficult lighting conditions, when enlightenment gives out “all possible and even some impossible” (c) (Dr. Breen) special effects. In general, the experience of using this lens was very unusual and entertaining.

Below are examples of photos taken with the adapted lens on a Sony A7s camera in APS-C mode.

Part of the photo was converted to b/w using Silver Efex 2.

Conclusions

Specialized infrared military optics, of course, inherently cannot be any equivalent to ordinary ones, if only because of color reproduction. However, for art photography, this is a truly unique tool that has no analogues among conventional photo optics, with a very peculiar pattern and quite sane optical quality - this is far from hipster monocle from a helios lens. In addition, no one bothers to use such lenses for their intended purpose with cameras without an IR filter, which are usually used by astrophotographers - here this lens has almost a twofold advantage over conventional lenses due to high light transmission in the IR region. In a word, if you have an extra tank in your household or you are for disarmament and world peace, this lens is for you!

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Add a comment: Pawel

 

 

Comments: 12, on the topic: Demilitarization: 50mm F/1.5, TVNO-2B tank night vision lens adapted for mirrorless cameras. Review from Rodion Eshmakov

  • LoliFromFutanari

    Thanks for the review! Rodion, you don’t happen to have in mind affordable and more mass-produced lenses similar to this one with a similar glow and softness. You are also interested in the possibility of installing them on EF-s with adapters.

    • Rodion

      Hello! Look towards Triplet 78/2.8.

  • Yuri Molchanov

    Thanks for the great review! I really want to do something like this, but the children grew up and threw away all the tanks.
    One hope now for ensigns!

  • Zheka

    The picture is nice, soft, for the video I think the most

  • Pawel

    We should try to remove such a sight from a German tank, I think the quality will be better). By the way, there is a blue-eyed Helios 44 from the start, it still can’t be adapted, you need to try it, maybe bw will go great on it.

  • Dim

    An amazing result, considering where the lens was picked from. The picture is pleasant - it is clear that at one time they did everything they could for the cultural development of tankers.

  • Dmitry Ivanov(St. Petersburg)

    Thanks for the hard work and interesting review! I remember once Nevzorov in 600 seconds talked about lifeless tanks near St. Petersburg and they say many “anti-militarists” of the 90s picked out a lot of everything interesting for civilian life from there) I liked the retro pictures!

  • Dmitry Ivanov(St. Petersburg)

    ownerless)

  • Oleg

    Thanks! interesting photos)! ... sharp and clear!

  • Jea reth

    Truly, make photo, not war

  • Rodion

    I have 2 of these lenses, they can be purchased from me for $80 and $85. Write to mail rudzil@yandex.ru or on social media!

    • Rodion

      Offer not valid)

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