10x50 kind of represents the king class of hand-held binoculars. This is so because a magnification of 10x is about the limit of what can be hold without any extra support and without intolerable loss of resolution. Also, the resulting exit pupil of 5mm is a reasonable compromise, ideal for an all-around glass, offering some low light capabilities without the excess weight of specialized night glasses. Last not least, it is fairly easy to construct 10x50 devices with nice wide apparent angles of view, making them more attractive to those who can't accommodate with the tunnel view of, e.g., 7x50 binoculars.
It is therefore not surprising that 10x50 binoculars on a high quality level have been available since several decades, because each company aiming at the quality market was supposed to have a 10x50 in their line of models, creating a highly competitive environment. In this review, the latest newcomer to the high-end 10x50 family, introduced by Fujinon, is competing with Docter's Nobilem, arguably among the best 10x50 Porro prisms made so far, and the classical Jenoptem of Zeiss (Jena).
Fig.1: The Fujinon 10x50 FMTR-SX. Note the huge size of the oculars.
In recent years, Fujinon has successfully established a position in the market of quality binoculars. Innovative technique and also the courage to experiment with exotic specifications (like the 25x150 for amateur astronomy) have contributed to the high reputation Fujinon has achieved by now, more in the US than in the conservative European market. The 10x50 FMTR-SX is a rather new member of a line of high-end Porro prism glasses, which also contains an 8x30, various marine 7x50 models, a 10x70 and 16x70 model. 'F' stands for 'flat field', i.e an extra field flattening lens is employed in the ocular to extend a high level of resolution over a wider field of view. 'MT' means 'marine tested', i.e. the device is water-proof according to US mil. standards. 'R' is the rubber armoring, and 'SX' stands for a patented electron-beam coating technique, supposed to increase the transmission rate of the binocular to almost incredible 95%. This glass has got individual eyepiece focusing and can apparently be ordered with reticle and/or laser protection filters, which indicates that Fujinon is aiming at the military market, too (if I am right, the US Army is already using Fujinon devices). The price for the 10x50 FMTR-SX is about 700 Euro.
Fig. 2: The Zeiss Jena Jenoptem 10x50W. The rubber eye-caps were not standard.
Whether it was called 'Dekarem', 'Jenoptem', 'Aus Jena', or, after 1991, 'Docter Classic', it stood for more or less the same product. According to Docter, this binocular was, in the present form, computed already in the late 1940s (as were the 8x30 and 7x50), and its optical formula remained unchanged over half a century. However, the surface coatings were improved a few times, and from 1978 onwards all models were equipped with multilayer coatings. Also, countless constructional changes were implemented over the years, to reduce the number of parts and improve the efficiency of assembly. Different names were dictated by the importers only, and the same instrument was usually produced with various different name plates. The 10x50 is identical to the 7x50 except the oculars. The Jenoptem 10x50W to be tested has a multilayer coating and is equipped with a central focuser. It can be frequently found on E-bay for about 200 Euro in good condition.
Fig. 3: The Docter Nobilem 10x50 B/GA. The focusing wheel is located in the center.
Around 1985, Zeiss Jena introduced a new high-end line of Porro Prism binoculars, which originally included the 8x50 Octarem and the 12x50 Dodecarem, was then renamed to 'Nobilem' and supplemented with a 10x50 and several 7x50 models. When Docter took over the Zeiss plant in 1991, they first kept both, the Nobilem- and the Classical line, but the latter was discontinued after a few years. Nowadays, the 8x50 and 12x50 are replaced with the 8x56 and 15x60, respectively, whereas the 7x50 and 10x50 are still in production. The rubber armoring was introduced in 1993, adding the letters 'GA' ('Gummi Armierung') to the complete specification Nobilem 10x50 B/GA. The 'B' stands for 'Brillentraeger' (spectacle wearer), but the eye relief of 15mm is apparently a little short for an easy use with eye-glasses on. The focuser is located near the center so that focusing is possible while the instrument remains well balanced. In the Nobilem, the two Porro prisms are cemented to reduce the number of air-to-glass transits and thus increase the transmission rate. The price is a little above 600 Euro.
Fig. 4: The Nobilem, Fujinon and Jenoptem
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) | |
| Fujinon 10x50 FMTR-SX | 6.5 | 65 | 20 | 5 | 1.5 |
| Nobilem 10x50 B/GA | 6.8 | 68 | 15 | 5 | 1.4 |
| Jenoptem 10x50W | 7.3 | 73 | 10 | 5 | 1.05 |
Image sharpness: A field of 65 degs. sharp to the edge? It sounds like a marketing gag, but the Fujinon comes quite close to this ideal. During day-time observations, the image looks in fact sharp almost to the edge. The test in the night reveals that inside almost 90% (radial) of the field the stars remain point-like. Even at the edge, the distortion is low. The Fujinon thus reaches the sharpness of the Russian BPO 7x30, and this at a wider field. The Nobilem comes next with a field of 75% of point-like stars. Its outer field sharpness is somewhat lower than the Nobilem's 8x50. During daytime, the difference to the Fujinon appears rather moderate, but at the night sky the Fujinon clearly gets the point. The Jenoptem is, like the competitors, razor sharp in the center, but the image quality quickly degrades towards the edge. I estimate that stars remain clean within about 60% of the field, and close to the edge they almost disappear.
Image color: All three of the glasses provide a nice neutral image color. I can't see differences of any relevance.
Rectilinear distortion: All three of them show a slight pincushion distortion which is helpful to eliminate the globe effect . The Fujinon seems to display somewhat less pincushion distortion than its contenders, without suffering any serious amount of globe effect.
Stray light: Light from sources outside the field of view can nevertheless enter the instrument through large angles and illuminate the internal tube walls, are in parts scattered back into the optical path and produce a diffuse illumination of the image. In many cases, this stray light is visible as a diffuse ring close to the edge of the field. None of the tested binoculars is suffering significantly from this effect. During daytime, the images are free of any signs of stray light. More critical is the situation of twilight, e.g. after sunset, when the sky is much brighter than the objects to be observed, and the observer's pupils are opening to 5mm so that the contaminated edge of the exit pupil can't be avoided any more. The Fujinon and the Jenoptem then show some signatures of stray light on a low-to-moderate level. To my surprise I found the Nobilem to be practically free of stray light. A surprise, because the older Nobilem 8x50 had some trouble here, as mentioned in another test. Searching for the reason, I found that the finish of the inner tubes has been improved since then: The old, dull dark-gray finish has been replaced with something of the same color but much rougher surface. It almost looks fluffy and seems to effectively absorb any reflections.
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. With some distance, the Fujinon performs best here. Even when observing the full moon, there are no reflections of any relevance visible. At partially full moon, this binocular is able to display the extremely high contrast between the illuminated and shadowed parts of the moon craters, and this is, combined with the high degree of sharpness, an impressive experience. The Nobilem exhibits essentially one diffuse spot of rather low intensity when observing a bright point-like light source. The suppression of ghosting is thus on a high level, too. The Jenoptem displays one bright spot and a couple of diffuse spots at the same object. The bright spot, however, is quickly leaving the field when moving the light source away from the center. Compared to the Jenoptem 7x50, the 10x50 leaves a better impression.
Low light performance: With a transmission rate of 95%, I expected the Fujinon to show a brighter image at low light than its competitors, but I didn't. Giving it a second thought, I realized why this was based on a misunderstanding: Having no numbers for the transmission rates of the Jenoptem or Nobilem, what I know is that the singly-coated DF 7x40 had got a transmission of 75% (without reticle). The step to multilayer coating is a big one, so probably the Jenoptem is not far away from 85% transmission, and the Nobilem will have another few extra %. In relation to the Jenoptem, the Fujinon then gets 12% more light, which corresponds to only 3mm of extra objective size. In other words: Comparing the light of the Fujinon with the Jenoptem is like comparing a 10x50 with a 10x53 binocular, and now it is obvious why it is so difficult to see any difference. It took me some efforts to finally verify that the Fujinon and Nobilem show a little more structural details at low light than the Jenoptem, and this may as well be due to reasons like better contrast (Fujinon) or less stray light (Nobilem). All in all, the differences are subtle and I doubt whether they are of much practical relevance. As a cross-check, I once took my Nobilem 8x50 and got a much brighter image than anything produced by the 10x50 glasses. We may conclude that whatever high quality coating is applied, it won't be able to make a 10x50 a good night glass. However, the coating is of importance somewhere else: Whatever light goes through the instrument can't be reflected to cause any other trouble (see the ghost image section). And here the improvement with the Fujinon is huge: With 5% non-transmitting light, the remaining noise is reduced by a factor of three compared to the Jenoptem (if 85% transmission is assumed).
| Angle of | Image | Stray | Ghost | Low | Image | Mechanical | Final | |
| field | sharpness | light | image | light | color | construction | score | |
| Fujinon 10x50 FMTR-SX | 1 | 3 | 1.5 | 3 | 2.5 | 2 | 3 | 16 |
| Nobilem 10x50 B/GA | 2 | 2 | 3 | 2 | 2.5 | 2 | 2 | 15.5 |
| Jenoptem 10x50W | 3 | 1 | 1.5 | 1 | 1 | 2 | 1 | 10.5 |
The 'final score' is the sum of the individual scores and is intended to serve as an orientation only. Generally, it would be an over-simplification of the matter to just look which binocular has got the highest score, because it would obscure the individual features of the devices which differ quite a lot among each other.
The Fujinon was supposed to be a new player in the game of high-end Porro binoculars, and this test is clearly supporting its claim. Its only weakness is a minor sensitivity to stray light. This test also confirms the Fujinon's reputation to be especially suitable for astronomy. The excellent ghost image suppression, and the corresponding high contrast, is a key feature for observing bright objects with dark background. The moon through the Fujinon was the best I have seen so far in any hand-held instrument. Also, the almost edge-to-edge sharpness comes handy especially on the night sky, where small distortions of star images are immediately visible, whereas in the forests it is of little relevance whether the edge of the image is super sharp or not. Finally, there is the feature of individual ocular focusing. I have generally no problems with this technique, after some years of using military optics. However, these were always of 7x-8x magnification. At 10x, and with a weight of 1.5 kg, it is a bit more involved to achieve a fine tuning of the focus, and for the stars this has to be done only once. To make full use of the instrument's resolution in astronomical observations, I suggest to employ a tripod.
A precise focusing is easier with the Nobilem because of the conveniently located focusing wheel. This is not the only argument for the Nobilem, which is slowly approaching its 20th birthday, to still remain in the game. I have noticed that the technical development has not stopped over the years. Compared to my (older) Nobilem 8x50, the stray light suppression has been significantly improved and has now reached the level of the NVA DF 7x40. Also, a slight yellow tint, which was there in the 8x50, is gone in the 10x50, which, of course, has got different oculars and also a different coating. This coating is not quite of the spectacular quality as the Fujinon's, but sufficient for the Nobilem to remain a state of the art all-around glass.
This test might leave the impression that the Jenoptem 10x50W is of rather low quality, but the opposite is the case. In my opinion, the 10x50 is the best among the three Jenoptems I have tested by now, with wider field and better ghost image suppression than the 7x50W, and much better stray light suppression than the 8x30W. It were the excellent competitors which didn't allow the Jenoptem to show its strengths. Still, it is a versatile all-around glass. I am not sure whether I would like to carry the 1.5 kg of the Fujinon or the 1.4 kg of the Nobilem out for a long walk, but with just above 1kg the Jenoptem looks inviting. As a reward, the Jenoptem offers a pleasantly wide image, not as perfect as the Fujinon's or Nobilem's, but for one third of the price.
Docter Optics, producing the Nobilem 10x50 B/GA
Last updated: 2003