Review: 8x30 Kern Aarau vs. Hensoldt Fero-D 16 vs. IOR B/GA

by Holger Merlitz

In a previous review , 8x30 binoculars, formerly employed in the Bundeswehr, were discussed, and in another review , two high quality 8x30 binoculars were compared to the current Hensoldt Fero-D 16 of the German armed forces. The latter is now once more taking part in another competition, this time against two other military binoculars of present days. All three competitors can be purchased either on the surplus markets (Kern, Fero-D 16) or new (IOR) for a price ranging between 250 and 300 Euro.

With such a price tag one should not only expect a state of the art optical design and a coating of fairly high quality, but also a reliable, rugged and weatherproof mechanical construction. The latter features are nothing less than mandatory for a military device. Luxury accessories like oculars for eye-glass wearers, a short close-focusing distance or screw in/out eye-cups are not on their list of features, and, as common in military binoculars, the convenient central focuser is absent - sacrificed for the improved weather resistance of the individually focusing oculars.

Fig. 1: The Kern Aarau 8x30

Since decades, the Kern company, located in Aarau (Switzerland), had equipped the Swiss armed forces with binoculars of high quality. The device to be tested (made in 1987) was the latest development of their 8x30 line, with rubber armor and a very characteristic construction of its hinge. It must have been introduced sometimes during the 1980s - there exist models made in 1980 which still were of traditional construction without rubber armor. In 1988, Kern was taken over by Leica, and since that time the binocular carried the Leica label. That is the reason why it is often referred to as Kern/Leica or Leica/Kern binocular. I am not aware of any constructional modifications implemented by Leica after 1988. There exist versions with or without Laser protection filters (this one is without), and different reticles were installed for service in either land- or anti-aircraft forces. The eye-cups fold down but then still remain hardly suitable for use with spectacles. In good condition, this binocular sells on e-bay for little below 300 Euro, often with laser filter. Nowadays, the factory in Aarau is completely shut down and these binoculars are probably not produced any more.

Fig. 3: The IOR B/GA 8x30

Quality binoculars for the Romanian army are produced by IOR-Bucuresti, founded in 1936 and from 1937 to 1945 part of the war-industrial complex of the occupying Germany. IOR stands for 'Industry Optic Romania'. According to their web-page, they are in collaboration with German manufacturers and employ glass made by Schott for their lenses. Apart from the 8x30, they produce devices of 7x40 specification, which once were exported to the Soviet army, as well as 10x40 and 10x50 binoculars. The IOR 8x30 to be tested was produced in 2004 and comes with a new rubber armor, covering the entire body (in earlier versions only the prism housings were covered). As is the case with all IOR binoculars, it can be ordered with or without reticle (this one is without). The eye-cups look down-foldable, but are actually not! Unless they are cut down, they are not at all usable with spectacles on. This binocular can be purchased new from US or British Internet dealers and sells for around 280 Euro.

Fig. 2: The Hensoldt Fero-D 16

The Fero-D 16 is one member of Hensoldt's latest line of binoculars, developed from 1982 onwards, which also contains a 7x50 (Fero-D 18) and 10x50 (Fero-D 19). They seem to be exclusively produced for military use, and come with a reticle and additional built-in filters against laser light of 1064 nm wavelength, i.e. within infrared range. 'Fero-D' is the short form of 'Fernrohr-Doppelt', meaning 'double-telescope'. With its introduction to the Bundeswehr - essentially during the 1990s - it replaced the Steiner 8x30 Fero-D 12, which was in service since the early 1970s and which had itself replaced the old Hensoldt DF of the 1950s. It is of roughly the same size and weight as the DF, but shows the characteristic 'bent shoulder' and is nitrogen purged to prevent internal fogging. This new version has got a longer eye-relief but a reduced field of view. The individually focusing oculars are equipped with down-foldable rubber eye-cups for spectacle wearers, although the eye-relief of 14.5 mm is barely enough for a comfortable use with spectacles on. I don't know of any official retailers, but the Fero-D 16 is sometimes found on E-bay in used but good condition and then sells for 250-300 Euro.

Fig. 4: The Hensoldt Fero-D 16, IOR B/GA and Kern Aarau

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)
Kern 8x30 8 64 14(a) 3.8 0.58
IOR 8x30 B/GA 8 64 14 3.8 0.66
Hensoldt Fero-D 16 7 56 14.5 3.8 0.65

a: Estimated value

Optical performance

Angle of view: With 8 degs. true field of view, both the Kern and the IOR are wide angle binoculars. The corresponding 64 degs. apparent field provide an excellent overview of the scenery around - a feature not without relevance for military binoculars. In contrast, the Hensoldt's 7 degs. field appears somewhat narrow, and it is in fact below average among 8x30 binoculars, where larger fields are easily achieved without the need of large and bulky prisms.

Image sharpness: All contenders produce an image that is sharp in the central region and then gradually becomes softer towards the edge. During the star test, the Kern and IOR begin to show some distortions of the star-image from about 60% (radial) off the center, and close to the edge the stars are strongly deformed. Through the Fero-D 16, deformations start at 70% and remain moderate towards the edge. Although the Hensold's image, compared to its competitor's, appears to be somewhat better corrected, this is the result of its smaller field rather than due to superior performance. Altogether, the close-to-edge sharpness of these binoculars is on average, but not impressive. If compared to the high-end Nikon SE or Fujinon FMTR-SX, displaying 85% of the field without any obvious aberrations, one thing becomes clear: For the extra money we could buy oculars of more sophisticated construction, which apparently had been too costly to be implemented here.

Image color: The Kern and the IOR show a neutral color rendition, whereas the Hensoldt displays a slight but visible green tint. This is the result of its laser protection filters. Though optimized to block infrared light of 1064 nm wavelength, these filters also cut off 10% of the visible light, mostly from the red part of the spectrum. The remaining transmitted light then looks greenish. Despite of that loss, the image contrast is quite good and clearly superior to the old DF.

Rectilinear distortion: All three binoculars show a little pincushion distortion as it is commonly employed to compensate for the globe effect and provide a smooth panning of the image.

Stray light: Diffuse stray light, which originates from light sources (e.g. a bright sky) outside the field of view and which could reduce the contrast of the image, especially if shadowed areas have to be observed, should be properly shielded to maintain a high performance of the instrument under difficult viewing conditions. This is masterly done in the Fero-D 16, which in almost every situation displays an image of high contrast. The Kern comes next, producing a slight diffuse reflex, visible especially under twilight conditions. Still, its performance is high. The IOR has got some weak points here. Looking into the objective tubes one easily detects large areas of highly reflective, unshielded prisms, and this must be the origin of a prism leak which produces a wedge-shaped reflex just outside the exit pupil. Under dim light, when the eye's pupils expand, they easily touch this side-pupil and the contrast of the image is suffering. Such effects are easily avoided and I wonder how a design team as professional as the IOR's was able to oversee this flaw.

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. Again, the Hensoldt, despite of its additional optical elements, performs best, closely followed by the IOR. Actually, through the right tube, both are almost even, since the reticle of the Fero-D 16 produces a dim reflex (the IOR is without reticle), but through the left tube the image remains almost clean. This indicates a high quality coating applied for the Hensoldt, although the IOR's is fine as well. Here, the Kern exhibits a weak point. The full moon produces various reflexes, some of them being de-localized and leading to a reduction of the contrast. It may be that later versions of this binocular (i.e. after 1987) came with an improved coating. If Leica ever faced the situation to decide how to improve this glass, they should have come to the conclusion that the implementation of a state of the art coating had been an efficient way to do that.

Low light performance: The small exit pupils of these binoculars do not suggest them to be great performers under low light. Their aim of construction was compactness and low weight rather than ability of light gathering. In fact, during night these glasses are easily outperformed by any 7x40 binocular. The differences between these three competitors are comparably small. I was unable to detect any significant difference in the performance between the Kern and the IOR, indicating that the light transmission is close to equal. As mentioned above, both are potentially suffering a performance loss in case of residual twilight (IOR, stray light) or strong light sources (Kern, ghosting). The Fero-D 16 is more robust against these effects, a fact which almost compensates for the light reduction caused by the laser protection filters. Well - almost. If the residual light is very low, then the 10% loss becomes a dominant factor and the Hensoldt is unable to keep up with its competitors.

Mechanical construction

These devices were constructed for military service and consequently are rock solid and close to indestructible. The individual eyepiece-focusing makes them essentially water proof, and the Hensoldt is additionally nitrogen purged to prevent internal fogging even under most adverse conditions (I have no information about whether the Kern is nitrogen purged as well). All three of them are covered with a full body rubber armor. The IOR feels especially robust, with all moving parts going smoothly but being stiff enough to stay where they were left as long as not intentionally operated. The Hensoldt's oculars turn a little too easily, and the Kern's hinge appears a little too loose, but both effects may be addressed to their higher age compared to the IOR which was purchased new. As mentioned above, none of them is comfortably operated with spectacles on. I prefer the objective covers as they are implemented in the IOR, because they snap in and remain firmly closed, whereas the Hensold's are much too loose and annoyingly have to be folded inside-out during observation. The Kern does not come with any objective covers, but with individual ocular covers, which are not there in the IOR. The Hensold's oculars are protected with a single rain cover as it is common among military binoculars. The Kern is a little more compact and of less weight than its competitors, but the difference is less than significant.


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
Kern 8x30 2.5 1.5 2 1 2.5 2.5 2 14
IOR 8x30 2.5 1.5 1 2 2.5 2.5 2 14
Hensoldt 8x30 1 3 3 3 1 1 2 14

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

This was a competition between three binoculars of about the same performance level, although they were exhibiting quite individual patterns of strong and weak points. The fact that the Hensoldt ended up on a level equal to the other two devices was entirely caused by the laser protection filters. After their removal, both color rendition as well as low light performance were likely to be on par with its competitors, and the Hensoldt would have won this competition. One should also be aware of the fact that the majority of Kern/Leica binoculars sold on e-bay appear to have these filters, too, and they would consequently be suffering from the same performance loss as did the Fero-D 16 in the present test. I generally suggest to look for binoculars without such filters to make full use of their abilities. Regarding the IOR, the outcome of this test suggests that any survey on quality military binoculars is necessarily incomplete without the inclusion of these Romanian products. The larger IOR 7x40 had already demonstrated its qualities in another review.

These binoculars are of middle class price and quality and they have proved to reach a decent performance level. On the strong side was a degree of ruggedness and weather resistance, not easily found for a price tag below 300 Euro. Optically, they were good but obviously behind the top class. Each of these binoculars has shown its individual weakness: The Fero-D 16 came with a small field of view, the IOR displayed problems with stray light, and the Kern with ghosting. Altogether, I am a little hesitant to suggest the purchase of any of them for a price which it is typically asked for. Instead of spending close to 300 $US, one may consider to add another 50-100 bucks to find an off-sale Fujinon FMTR-SX.


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