Review: Kronos BPO 10x50 vs. Kronos BP 12x40 vs. Baigish BPOc 10x42

by Holger Merlitz

Russian binoculars have got the reputation of being cheap, of crude - if not barbaric - design and sometimes with surprisingly good optics. And, of course, all of them were serving the red army to prevent imperialism spoiling the better part of the world. Ironically - this pre-justice seems to be correct in some aspects. There was in fact no market for civilian binoculars in the USSR of the cold-war times. Binoculars were regarded as military equipment and few of them found their way into the private households. After 1990, the big optical manufactories had to shut down major parts of their military production lines and tried to re-orient themselves toward the civilian markets in order to survive. Nowadays, lots of different binocular models of military origin are freely available to be purchased all over the world, some of them partially modified to better serve the needs of the civilian customers.

This review compares three of these binoculars of military origin which appear rather different on the first sight, but which are sharing a fairly high magnification of 10x-12x and a price tag between 100 and 120 Euro, i.e. they are reaching beyond the low-range class. With their price tags they are already facing stiff competition from China, producing glasses of rather modern, decent looking design and a mechanical construction that in many cases is not only feeling better but seems to be based on an more precise machining process than the often all too sloppy Russian competition. This review is then also an attempt to critically discuss the performance and the potential of these Russian binoculars on a market which is increasingly becoming tight and which does not excuse the absence of technical innovation on the long sight.

Fig. 1: The Kronos BPO 10x50 (military version with reticle)

The Kronos BPO (or BPSH) 10x50 is produced at ZOMZ (Zagorsky Optiko-Mekhanichesky Zavod) as a variation of the BPWC 10x50 (or BPSHC, with central focuser and no reticle). It is one representative of a product line including an 8x40, 12x50, 16x50 and 20x50, all of them with individually focusing oculars and a rangefinder reticle. While the civilian Kronos BPWC line (including the 6x30 , the 7x35 and the 8x40 ) is frequently listed on Ebay, the military BPO items seem to be more difficult to find (thanks to Hans Weigum who got this one in Moscow). It is interesting to note that the BPWC claims a field of view of 7.5 degs while the BPO is specified with 6.8 degs only. A close inspection revealed that both optical setups were identical except for one additional field stop implemented behind the prism exit (on the ocular side) inside the BPO, a feature not present in the BPWC. As will be discussed later, this seems to be of relevance for the stray light resistance of this binocular. On the ZOMZ site it is listed to sell for 90 US$.

Fig. 2: The Kronos BP 12x40

The Kronos BP (or B-12-1) 12x40 binocular is produced at the same ZOMZ plant as the 10x50, although of entirely different design with long prism housings and without attached objective tubes, giving the body a rather stubby and compact shape. Despite of its high magnification, it is just usable without tripod (except for rather delicate astronomical observations) thanks to its moderate weight and ergonomic construction. The covers of the prism housings are carefully sealed to get the instrument watertight. As is the case for all ZOMZ military binoculars, the BP 12x40 is claimed to be operational from -40 to +45 degs Celsius. It is listed to sell for 124 US$, though this may be varying a little depending on the online dealer (I found this one on HUPRA for 99 Euro).

Fig. 3: The Baigish 10x42. The serial number indicates its production in 2000

The 10x42 BPOc (Baigish) is the big brother of the famous BPO 7x30 and produced at KOMZ (Kazansky Optiko-Mekhanichesky Zavod). Both seem to share the same prism housing and ocular construction, although one feature has been changed: Whereas the 7x30 was initially equipped with an internally focusing ocular and twist-up ocular cups, this was replaced sometimes in 1994 with an external focuser and fixed hard rubber eye-cups. The latter construction is also realized in the 10x42. On the first site these rubber cups do not seem to fold down, but I was informed that they do with a little bit of brute force, and in fact it works out so that it is possible to make use of the generous eye-relief of the eyepiece. This heavy glass is protected with a thick rubber armor and claimed to be operational between -40 and +50 degs Celsius. On HUPRA it sells for 119 Euro.

Fig. 4: The Kronos 12x40, Baigish 10x42 and Kronos 10x50

The following table summarizes some of the specifications of the contenders.

  Real angle Apparent angle Eye relief Exit pupil Weight
  of view (deg) of view (deg) (mm) diam. (mm) (kg)
Kronos BPO 10x50 6.8 68 16.5 5.0 1.0
Kronos BP 12x40 5.6 67 12 3.3 0.83
BPOc 10x42 Baigish 5.6 56 21 4.2 1.2

Optical performance

Angle of view: The Kronos BPO 10x50 is specified with 6.8 degs and this provides a nice wide apparent field of view of about 68 degs. Amazingly, the civilian version (BPWC or BPSHC), which is supposed to have 7.5 degs, is actually not visibly wider than 6.8 degs, despite of the missing field stop (as mentioned above). The reason is: In order to see the full field, the eyes had to come very close to the eye-lens, but once this is done, the field is narrowed down by kidney-beaning ('blackout') so that effectively the usable field of view remains around 6.8 degs. I had already observed in earlier reviews that the usable fields of view of the BPWC 6x30 and 8x40 were smaller than specified, always a little below 70 degs apparent field. For the Kronos 12x40 I have measured a field of 5.6 degs, which yields a wide 67 degs apparent field. The Baigish 10x42 is, with 5.6 degs as well, somewhat narrow for a 10x binocular. The corresponding 56 degs of apparent field (at infinity setting) are a little less than specified, but they seem to marginally increase once it is focused on close distance objects. The 10x50 and 10x42 have got a sufficiently large eye-relief to be usable with spectacles on.

Image sharpness: The Baigish 10x42 is by far superior not only to its competitors, but to any binocular of this price class, except for its little 7x30 brother. The star test delivers point-like stars over more than 90% (radial) of the field, and even at the edge their distortions remain low. In fact, such an outcome is rarely found in binoculars of any price class, and the reward for its extremely sophisticated ocular construction, containing as many as 7 lens elements. The Kronos 12x40 displays point-like stars over 60% of the field, with quickly decreasing image quality beyond that. At the edge, the stars are grossly deformed. The Kronos is, as are the other contenders, nicely sharp in the center with gradually increasing distortions beyond about 50% of the field. This increase is somewhat slower than observable in the 12x40, that's why I regard their overall performance to be on the same level.

Image color: None of the three binoculars has got a neutral color rendition. As it seems to be a mandatory feature among all Russian glasses, they provide a moderate (Kronos 10x50 and 12x40) or strong (Baigish) yellow tint. In case of the Baigish, the origin of the yellow color has been traced back to one single lens element of the eyepiece, as is nicely demonstrated on this photo by Fan Tao. Following Albrecht Koehler's argumentation (German language), the thick negative element could require Flint-glass (SF3) which usually turns black under radioactive radiation - the corresponding radiation resistant glass (SF3R) has got that yellow cast. Assuming that all Russian binoculars are using this glass type, then the strong yellow tint of the Baigish is simply related to the fact that this lens element is particularly thick. In contrast, the yellow color of the two Kronos glasses is not disturbing but actually of some use under gloomy weather conditions, where the yellow cast makes the image appear somewhat brighter compared to a completely neutral binocular.

Rectilinear distortion: The Kronos 10x50 displays a slight pincushion distortion as it is commonly employed to compensate for the globe effect effect and provide a smooth panning of the image. Both the Baigish and the Kronos 12x40 are almost free of pincushion distortion. As a benefit of this feature, straight lines remain straight up to the outer areas of the field. Once the binocular is panning, however, the image seems to roll over the surface of a ball (i.e. an object appears a little larger at the center and seems to shrink when shifted close to the edge) to create the globe effect. The existence or absence of pincushion distortion is therefore no suitable parameter to evaluate the quality of the binocular but a result of the individual design philosophy, and it perhaps provides a hint about what this binocular was supposed to be used for. Without distortion, it is optimized to observe details of distant, non moving objects. With pincushion distortion, the glass is rather usable for surveillance applications where a large area has to be kept under observation.

Stray light: This effect may show up once there are bright objects outside the field of view and throwing light into the binocular, illuminating inner walls of the objective tubes and/or the prism construction. Once parts of this light are scattered into the main light path, they contribute to the image, producing a 'white out', a reduction of contrast by diffuse stray light. This effect is most easily found during twilight, when residual illumination of the sky is disturbing the observation of objects in shadowed areas. A proper anti-reflective finish and baffles as well as properly shielded prisms help to reduce the impact of stray light. It is interesting to find the Kronos BPWC 10x50 (the version with central focuser) suffering badly from stray light, whereas the almost identical BPO 10x50 shows only moderate signs of this effect. As mentioned above, the latter is equipped with an extra field stop, and this apparently plays an important role for the stray light resistance of the military version. The Kronos BP 12x40 also displays stray light on a moderate level, whereas the Baigish 10x42 has got some more problems here, with stray light on a moderate-to-high level. The source of trouble seems to be its objective tubes, where a couple of structures are throwing a bright reflex into the optical path. The Baigish 10x42 is therefore much more prone to stray light than its smaller 7x30 version.

Ghost images: If, at night, a bright object (street lantern, moon) is positioned into the field, reflections on the air-to-glass surfaces take place, which can lead to multiple 'ghost' images of the light source. Here, the Kronos BPO 10x50 is clearly performing best, indicating a rather high quality coating. There is only one reflex through the right hand side, originating from the reticle, reaching a moderate-to-high level of brightness, the other reflexes remain on a low-to-moderate level. The Kronos 12x40 and the Baigish 10x42 produce a couple of ghosts, some of high intensity - high enough to suspect whether a few of the internal glass elements have been left entirely uncoated. The brightest stars are already able to produce a visible effect. This should not be the case with a binocular of such a price tag.

Low light performance: Taking a look at the exit pupil diameters, one may predict that the Kronos 10x50 is going to be best suited for low light conditions, followed by the Baigish and finally by the Kronos 12x40. This is exactly what comes out once they are compared after sunset with decreasing amount of twilight: The 12x40 becomes unusable very soon, showing an image which is increasingly lacking of contrast and surface details. This binocular is for daylight use only. The BPOc 10x42, initially suffering from stray light, performs better once the darkness is progressing. Still, it is not quite a good performer under low light and clearly outperformed by the Kronos 10x50. As a rule of thumb it is claimed that from about 5mm exit pupil onwards binoculars become usable under low light conditions, and the Kronos appears to support that rule. It is certainly not only the larger exit pupil, but also the fairly good quality of coating which makes the 10x50 looking strong under these conditions.

Mechanical construction

No doubt, the Baigish 10x42 is of most rugged construction. The body feels solid like a tank, the rubber armor is providing an extra protection against mechanical impact and further features like attached objective covers and the rain guard for the oculars make it a hard-core military device. Both Kronos binoculars are feeling solid as well, with metal bodies and a stiff central hinge movement. The ocular focuser of all three binoculars feels a bit loose, however. It is sometimes claimed that this is not the result of sloppy machining but a necessary feature to make these instruments work at temperatures as low as -40 degs Celsius, but I am not convinced. The East German EDF 7x40 had to pass the temperature test at -50 degs and nevertheless came with a sufficiently stiff focusing under room temperature. With their loose focuser, none of the three candidates is likely to be sealed well enough to take an immersion under water. It seems to me that the Baigish and the Kronos 12x40 are at least equipped to be splash-water proof, whereas the Kronos 10x50 might be in trouble during heavy rain. As mentioned above, the Baigish and the Kronos 10x50 have got an eye relief which is sufficient to make them usable for eye-glass wearers, but the eye-cups of the Baigish are quite difficult to fold down and the Kronos' eye-cups are fixed anyway, so that no individual adjustment of the eye-distance is possible.


The following table is supposed to summarize the above observations. The best performing binocular gets three points, the following contenders two and one, respectively. In case several binoculars are ranking equally, their scores are averaged.

  Angle of Image Stray Ghost Low Image Mechanical Final
  field sharpness light image light color construction score
Kronos BPO 10x50 2.5 1.5 2.5 3 3 2.5 1 16
Kronos BP 12x40 2.5 1.5 2.5 1.5 1 2.5 2 13.5
BPOc 10x42 Baigish 1 3 1 1.5 2 1 3 12.5

The 'final score' is the sum of the individual scores and is intended to serve as an orientation only.

The Kronos BPO 10x50 has got the best overall optical performance among these three binoculars. This is a well balanced construction in the sense that no obvious weak point was showing up to spoil the image. With its performance, it comes close to the Zeiss Jena Jenoptem - not bad for a binocular of the 100 Euro league. I have to point out that the same is not valid for the civilian BPWC 10x50, which is badly suffering from stray light. As mentioned above, the absence of a field stop is most likely the reason for that. I would strongly suggest ZOMZ to put it back where it belongs to - all the more since its removal did not serve the intended goal to widen the field of view. This field stop is an important ingredient of the optical design of this binocular. Another point is the camouflage painting of this instrument, giving it a cheap appearance. On the picture it is indistinguishable from cheap plastic binoculars offered for 15 Euro everywhere on Ebay, and hardly any customer shall be willing to spend the multiple amount for an identically looking item. A decent black painting would serve better. Even better were a thin rubber armor covering the body and thereby sealing the prism-housing covers, making the binocular splash-water proof.

The Kronos BP 12x40 is of reasonable performance for its price. Its most obvious weak point is the imperfection of its coating, making it prone to ghost images. Shifting that up to the quality level of the Kronos 10x50 would create an overall performance boost for this binocular, including a better contrast under low light conditions. The design of this glass is timeless and functional. I do not belong to those guys who always ask for modern looking stuff while the older designs are still working fine. One shortcoming of this instrument is its lack of eye-relief, but it is difficult to produce a properly long eye-relief if the focal length of the oculars is as short as required for a 12x40. One should accept the fact that the Kronos 12x40 has to be used without spectacles on, and under these conditions this instrument is producing a nice wide field.

The BPOc 10x42 (Baigish) is an instrument with enormous potential. Its image sharpness is second to none not only in its price class but even when compared to any of the upper middle-class. Its construction is rugged enough to make it usable under most serious external conditions. Unfortunately, there are a couple of flaws, serious enough to reduce its performance significantly. Its anti-reflection coating is not good enough. It should be improved up to the level of the Kronos 10x50 to make this glass competitive. Then there is quite a lot of stray light. Since this effect is absent in the smaller BPO 7x30, I assume its origin to be inside the objective tubes which require a more effective baffling. Also, the hard rubber eye-cups are not at all convenient to handle. I definitely prefer the older construction with twist-up eye-cups as it was realized with the 7x30 before 1995. Last not least: There is no law of optics forcing Russian binoculars to display a yellow image color. In order to survive against the quickly improving Chinese competition, Russian glasses have to switch to neutral glass types, because any color tint is regarded as a quality loss by almost every user. The BPO 10x42, with the above mentioned improvements, were able to compete with any upper middle-class product on the market and may easily sell for 250-300 Euro.


The civilian Kronos 10x50 on Fan Tao's page
The BPO 10x42 on Fan Tao's page


The information given in this report reflects the personal impression and opinion of the author only. I cannot guarantee for the accuracy of any given specification. I have neither been payed nor have I been supported in any other way to write this review.

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Last updated: 2004