A Brief Reaquaintance with my First Roof Prism Binocular.

The Barr & Stroud Sahara 8 x 42 binocular.

A work begun August 21 2020.

It was in October 2018 that I began my first, tentative adventures in surveying the  modern binocular market. I had entirely neglected the massive technological changes that had occurred in the industry that continued to drive quality up and prices down; indeed, just like what had already happened in the telescope market. With a background in astronomy, I had stuck fervently to my old 7 x 50 porro prism binocular from the late 1980s and wasn’t at all prepared for what three decades of innovation wrought to the consumer. And boy was I surprised after I received my first roof prism model – a Barr & Stroud Sahara 8 x 42 – and compared it with the ole clunker!

The smaller aperture Barr & Stroud had a brighter, sharper and more contrasty image than the ‘high quality’ 7 x 50 porro I had been gifted by a past girl friend.

I suspect that this revelation was not unique to yours truly. Indeed, I imagined that there must be hundreds if not thousands of amateur astronomers the length and breadth of the country who would have been equally shocked by comparing a modern, entry-level roof prism binocular to an old school porro prism exemplified in the 7x or 10 x 50! If that’s you, I can say, hand on heart, that you will literally be blown away by what can now be purchased for a very modest investment.

I had chosen Barr & Stroud solely on the basis of carefully assessing the many enthusiastic reports I had garnered about this old company that once supplied all manner of optical equipment to the British navy during two World Wars. But after the War years, the company experienced a barrage of new challenges that resulted in the company’s decline. Finally, in 1977, Barr & Stroud ceased to exist as an independent trader and with it, an industry that held many trade secrets on how to build a good binocular.

Then, round about 2010, the vintage brand reappeared with a new range of modern binoculars catering for the budget conscious/ beginner birder market. But it lo longer existed as an independent company. Rather it was bought out by Optical Vision Limited UK, who also own perhaps more familiar names like Helios, Acuter, Zenith and Fotomate. The Barr & Stroud Sahara 8 x 42 was an extremely delightful experience for me, and whetted my appetite for exploring the binocular market still further. And the rest, as they say, is history.

After I had acquired better models, I gifted the Sahara to my sister- and brother-in law who were also delighted with its performance and served them well on their many fishing and camping trips all over Scotland. During a recent visit to their home in the west end of Glasgow, I got another chance to evaluate it in light of everything I had learned about binocular optics testing in the subsequent two years. So I took it home and brought it on a couple of walks to see how well it was faring.

Exceptional Focusers

First of all, I was very impressed with its build quality; this was a fully weather armoured instrument with a light-weight polycarbonate chassis housing the properly multi-coated optics. The textured rubber and ribbed upper mono bridge design provides for easy and secure handling either with or without  gloves. The large, central focus wheel is notable; it is one of the smoothest I’ve personally encountered and that’s comparing it to a number of big brand models from Opticron, Zeiss and Leica! Indeed, having sampled several binoculars from Barr & Stroud including the more expensive Sierra, Savannah and Series 5 models offered by the same company, I can tell you in no uncertain terms that all of their focusers were superb. They all operated flawlessly with buttery smooth precision and zero backlash, whether constructed of metal or plastic. This can’t be a fluke; it must be attributed the the company’s attention to detail and considerable practical knowledge on how to design and execute a good focusing wheel on all its optical devices. Now, don’t get me wrong, I’m not suggesting that the Barr & Stroud binocular focusers can outdo top tier companies like Leica in terms of long term productivity. If I asked the same question a decade hence, I doubt I’d get the same answer. But so far, they’ve never failed to impress and have never let me down!

Something you’ll never see in a contemporary binocular discussion; comparing two models with a ten fold price differential in terms of ergonomics. Right, the Leica Trinovid HD 8 x 32 and the Barr & Stroud Sahara 8 x 42 (left).

Other ergonomic considerations

The twist up eye cups on the Sahara are fairly basic and are quite representative of what is provided in the lower tier of the market. That said, and unlike quite a few other models costing a few times more, these rubberised plastic cups still work fine after a few years of use. Yes, one cup is considerably stiffer than the other, but once fully extended, they click into place and rigidly maintain their positions, even after applying considerable pressure to them. Again, while the low-cost materials out of which they are constructed are fairly generic in a lot of entry-level models, these Sahara eye cups still work well because they were put together by a competent team of assemblers.

Ditto the rubber armouring used on the instrument. After giving it some close inspection, it has not peeled or come away from the chassis and retains a good rugged and grippy feel. I can’t say the same thing for a number of much more expensive models I’ve sampled including, most notably, the Nikon Prostaff and Monarch range of binoculars that are so popular today!

The same is true of the right eye dioptre on the unit. It has quite a bit of inertia, to use an old fashioned term, meaning that once it’s set it is very unlikely to move unless deliberately tampered with. Sure, it doesn’t have the sophistication of a lockable device seen on some more expensive models, but I consider this to be superfluous to the needs of the vast majority of glassers. It is an eminently practical solution still employed on some of the best binoculars on the market today, including the venerable Leica Trinovid HD shown above. Furthermore, although some of the company’s more sophisticated models such as Barr & Stroud’s excellent Savannah binocular, has its dioptre dial placed ahead of the focus wheel on the bridge, it is not necessarily a better solution, as I have discovered in extensive field use.

Optics

Although the Sahara lacks sophisticated optical refinements such as phase corrected prisms, it still serves up a good, sharp and bright image during ordinary daylight conditions. The field of view is wide (129m @ 1000m), but not so wide that the effects of off-axis field curvature, barrel distortion and astigmatism become overwhelming. I’ve lost count of the number of binoculars I’ve tested costing considerably more than this unit, that offered tack sharp images inside a central sweet spot, only to show horribly distorted and unfocused images in the outermost part of the field. An eminently sensible optical design would curtail field of view in order to maintain a decent level of off-axis performance that won’t be immediately off putting to a novice enthusiast. Indeed, in my own personal journey through the maze of modern binocular  brands, I have developed a strong preference for smaller, better-corrected fields than uber-wide fields showing too much off axis aberrations. For me, field of view is most certainly not king!

I never got a chance to test the Sahara binocular for light leaks in the customary (and, dare I say, much more discriminatory) manner, I’ve developed in my later binocular reviews, but I now have. My results show a significant amount of internal reflections as well as diffused light that was very similar in profile to an 8 x 32 model marketed by Eyeskey. I interpreted these results to mean that Barr & Stroud has been working with the same optical materials – lenses, prisms etc – used to construct many other entry-level roof prism models. These effects are easily seen in night time tests on street lighting, which show some internal reflections in the field of view and rather strong diffused light, indicative of possible homogeneity issues with the quality of the optical glass employed. What this means is that one might expect the Sahara to show up some glare and internal reflections when glassing a bright Moon(untested by the author) which will be inferior to more expensive models having higher quality optical glass and coatings etc. That said, the Eyeskey, costing about half the price of the Barr & Stroud Sahara, was not in the same league as the latter in daylight optical evaluations, showing a smaller sweet spot, more chromatic aberration and stronger off-axis aberrations.  All of these experiences allowed me to advance the following hypothesis regarding the differences between this less expensive Eyskey model and the Barr & Stroud(both of which are manufactured in China). Using the same quality of optical materials, differences in the assembly of such devices yields very significant differences in perceived optical quality. The Barr & Stroud Sahara is assembled by a more knowledgeable/skilled team than those assembling the Eyeskey marketed model. It’s all in the assembly!

Light Transmission Efficiency

Comparing the Barr & Stroud Sahara 8 x 42 to the Viking Optical Merlin ED 8 x 32( bottom).

As noted previously, The Barr & Stroud Sahara 8 x 42 does not have a phase coating applied to the roof prisms, nor does it have dielectric coatings to boost light transmission. I was able to detect a significant difference in the quality of the image a phase coating can do to the image in a previous communication, where I compared the views through the Sahara and the more expensive Sierra 8 x 42 model offered by the same company. Nor did the Sahara have any extra low dispersion(ED) lens elements to improve image contrast and perceived sharpness.

In many previous blogs, I demonstrated that ED glass does not significantly boost light transmission but I did attribute greater light transmission to the presence of dielectric coatings applied to the roof prisms. I was able to evaluate these technologies more fully in a side by side test I conducted recently between the 8 x 42 Sahara and the smaller Viking Optical Merlin ED 8 x 32, which does have all the aforementioned optical advances. By day, the Merlin offers up a sharper, more contrasty image than the Sahara but the differences are subtle and not at all like ‘night and day,’ as often reported by others. But testing at dusk – after sunset on a cloudy August evening – did reveal the significant advantages of having better coating technology.

All other things being equal you’d expect a 72 per cent light gathering boost for the larger aperture Sahara binocular. But in low light conditions, the larger exit pupil on the same binocular (5.25mm as opposed to 4mm on the Merlin), might be expected to further extend that advantage to the Sahara. My results showed that although the image was brighter in the larger aperture Barr & Stroud unit, it was much closer than I had expected! Specifically, the Merlin was showing how much more efficiently it was bringing light to my eyes than the Sahara. Its super-high reflectivity dielectric, and phase coated prisms, as well as better control of stray light, were certainly responsible for these gains in low light performance. That said, under fully dark adapted eyes on a Scottish August night, the larger aperture Sahara proved itself to be a better star gazing binocular, reeling in fainter stars and providing better views of a variety of deep sky objects. That’s due to the larger exit pupil in the 8 x 42 compared with the 8 x 32.

Conclusions

So, there you have it! Maybe you can better see why I would choose this binocular again if I were starting out. Now that the scamdemic has hobbled the economies of the nations of the world, millions more families are going to feel the financial pinch in the coming months and years. If you’re after a no-nonsense binocular that will give decent images of God’s creation for a price under £80 UK, you’ll be very hard pressed to find a better model than the Barr & Stroud Sahara 8 x 42. You don’t have to take my word for it either; check out the many reviews of this model online and also have a look at comments made about these models by experienced birders. Happy glassing and thanks for reading!

 

Bird Guide Commentary

Neil English sorts out the bull & bling from the salt & light of the binocular world. You can support his work by making a small personal donation, or by purchasing one of his seven books. 

 

 

De Fideli.

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