A Tale of Three Binoculars

My 30-year old 7 x 50 binocular.

 

It was just over 30 years ago when I was gifted a nice 7 x 50 binocular by my girlfriend. They featured a 7 degree field, multi-coated optics and BaK-4 porro prisms. They served me well all these years on holidays, walks and for casual stargazing. They weren’t cheap either. Lesser units would have fallen apart by now, but after trying a few modern binoculars out I knew that technology had moved on, mostly for the better.

And so had my eyes.

Now that I’m older, I wanted a binocular that had an exit pupil more suited to my age. I wanted an instrument that was more light weight, so that I could observe for longer without using tripods. I wanted a binocular that would do well in a variety of situations, from nature watching from dawn to dusk, and for astronomy. They had to be robust and ideally weatherproof to a degree. My ideal binocular views had to serve up sharp, colour pure views of autumn’s radiant hues but also allow me to throw caution to the wind and just enjoy the glories of the night sky from the comfort of a recliner. But which ones to buy?

Alas, I found that choosing a model that ticked all the boxes for me to be a daunting prospect! Today, we have so many makes to choose from; which is a good thing. My experience with telescopes came in very handy though. Not easily swayed by marketing gimmicks and wishy-washy hyperbole, I slowly pared them down to size.

I decided I wanted a fairly compact, full-size binocular that would offer good light grasp, so a clear aperture of 42mm would be about the minimum that would do the trick. I wanted a fully multi-coated instrument to maximise light transmission to the eye and reduce glare on bright objects to an acceptable minimum. They had to be well made with a decent warranty should they get damaged or worn out from regular use. And they had to present good value for my hard-earned cash.

I narrowed my search down to a good roof-prism binocular as these had many of the features I was looking for; small, light weight, decent light grasp, ultraportable etc. Two magnifications were considered, 8x or 10x. With 10x you’d get a smaller exit pupil and lose some advantages of using them in low light conditions. 10x would also introduce more shake and would be more difficult to accurately focus while in use too, so I decided on 8x; an 8 x 42 binocular.

I went to amazon.co.uk to check out the user reviews of a variety of models I had an interest in. In many ways, these types of reviews give the prospective buyer a more rounded view of what it’s like to use a given model, as they are often more honest and less biased than those offered by so-called ‘experts,’ who, more often than not, succumb to clever marketing ploys and had a tendency to push premium products over more economical models that might still offer perfectly acceptable performance. I found that birders, for example, often highlighted a variety of mechanical and optical features that were largerly superfluous to my needs. I didn’t really need super-fast focusing, locked in dioptre settings, nor ED elements in the objectives. At such low powers, one would be hard pressed to see the advantages of employing low dispersion glass and most of the online literature seemed to over-emphasise their advantages even though I knew that it would only make a small (insignificant?) difference to the views. Afterall, how many amateur astronomers insist on having ED finder ‘scopes eh? Why haven’t 8 x 50 ED finders or some such become the industry standard, if they really offered any tangible advantage over good ole crown & flint? The honest answer is that they’re unnecessary, and so can be dispensed with.

As a case in point, check out this user review of the Vortex 10 x 42 Diamondback roof prism binocular. The gentleman states that he was asked to try out the more expensive Viper model with ED objective elements in a blind test. He states that he couldn’t really tell the difference in field use. I have no reason to doubt the gentleman’s conviction. Why lie on such a trivial matter?

No, a good, no-frills, traditional achromatic binocular to match my average eyes was what I was shopping for!

I went with a company that had a long track record of producing high quality optics, as I reasoned that such knowledge would be invaluable in the construction of a well-made binocular. Many companies selling such binoculars were not long in the game though, so my instinct was to avoid them. I gravitated toward an old British firm that had produced optics for the military in two world wars; Barr & Stroud.

Now bought out by OVL, Barr & Stroud  re-entered the sports optics market by bringing out a range of affordable roof prism binoculars in an 8 x 42 format and my first purchase was the Sahara 8 x 42, which retails for about £70-£90 UK.

The Barr & Stroud Sahara 8 x 42.

 

Though under no illusions that these are British made, Barr & Stroud binoculars are now assembled in China, just like those marketed by Vortex (a US-based company) and many other companies. They are supplied with a nice, soft carry case, neck straps, a lens cleaning cloth and have a 10-year warranty.

The Sahara 8 x 42 binocular comes in attractive box with a good carrying case with the usual accessories.

 

The specifications of the Sahara 8 x 42 model can be viewed here.

The Sahara is a joy to use. It’s small and light weight (670g), has good eye relief (17.5 mm) and with its twist up eyecups, will allow those who must wear eye glasses (I don’t) to enjoy the expansive field of view (7.33 angular degrees). Images are bright and sharp and colour fidelity is sound. With its fully multi-coated optics, contrast and glare suppression are excellent too in comparison to my old 7 x 50s. You really have to look for chromatic aberration but it is there. You can best see it by focusing on the edge of a telephone pole against a bright, overcast sky background, but is minimal and not in the least bit intrusive(I’d say mostly bum-fluff). At the edge of the field, the image gets a little softer with some slight fringing during daylight hours but it will never be enough to disturb the vast majority of users. Focusing is smooth and intuitive, not overly stiff or loose and it has an excellent close focus distance of just under 2m (measured) to allow you to enjoy insects, flowers etc at close range. It also has adequate waterproofing for my intended uses for it.

Night time views were very impressive too. Stars are sharp and pinpoint across the majority of the field. Only by using a stable tripod, will you be able to notice a little defocus of the stellar images at the edge of the field. All in, I would rate the Sahara as very good and considering its modest cost; a great bargain in today’s market! These guys certainly know how to make a good binocular!

Shortly after purchasing the Saharas, I began researching the properties of roof prisms and discovered that they have a significant design flaw. In the roof prism design, the two halves of the collected light from the objectives travel through the prism independently and are recombined before reaching the eyepieces. Because the path of the two wave trains are of slightly different lengths, one half of the light takes a little longer to travel through the prism than the other. When the two halves of the image are recombined, the wave with the longer light path will be slightly out of phase with the light that undergoes the shorter route. This results in a combination of destructive and constructive interference of the wave trains, affecting the colour balance, contrast and fidelity of the binocular image.

Note that this flaw does not affect porro-prism-based binoculars!

By introducing a special phase coating to the prism undergoing the shorter light path, optical designers can slightly retard the wave train, thereby correcting the phase difference with the other wave train. This results in sharper, brighter images with higher contrast; in theory. As I researched this some more, I discovered that the result was quantitatively significant; 8 per cent according to the manufacturers. Intrigued, I looked for a Barr & Stroud model that had this phase coating as the Sahara’s did not have this technology built in and that quickly led me to their 8 x 42 Sierra model.

The Barr & Stroud 8 x 42 Sierra binocular.

 

Luckily, the Sierra was only a little bit more expensive than the Sahara. Full specs here.

Otherwise sharing very similar specifications to the Sahara, the Sierra 8 x 42 is also slightly lighter (650g), coming with the same soft carry case and accessories as the former. The polycarbonate body was also a little different in the Sierra compared with the Sahara, as the above images show. When it arrived, the first thing I did was undergo a test to see if there was any significant difference between the images. Examining a brightly lit scene with a trunk of a tree shadowed by some over-hanging branches and comparing the two binocular images, I must admit that the Sierra was that little bit better. It’s difficult to describe in words but I suppose I’d say that the Sierra image had a little bit more ‘zing’ to it. The image was that little bit brighter and the colours more vivid. Contrast was also better by a shade.

Based on this test, I think phase coating technology is definitely worth having. Subsequent research of other high-end and mid-priced binoculars revealed that they all possessed these phase coatings. I see them as increasing the overall efficiency of light transmission, improving the image in a way that the human eye would notice in a critical test.

In another test comparing my 7 x 50s to the Sierra’s, I had to immediately concede that the images in the latter were far superior to the old porro prism binocular. The image was actually brighter even though it only had 42mm objectives(as opposed to 50mm in the auld yin) and the contrast far superior. The Sierra also presented a larger field of view.

Man and his technology!

Before describing my experiences with the Sierra 8 x 42 in any more detail, I was curious to see how the unit would fare compared with a high-end binocular with roughly the same specifications. As luck would have it, my coalman is a keen birder and dabbles in hunting big game. He’s the proud possessor of a Swarovksi EL 8.5 x 42 binocular, which retails for about £1800 UK. When he came to deliver some coal I got chatting with him and asked him if he would be so kind as to bring them by some afternoon so that we could compare and contrast the images garnered by these binoculars. He agreed.

The Swarovski EL 8.5 x 42 roof prism binocular.

 

Though certainly not a ‘gayponaut’ (a word of my own coining, fomally defined as: an irrational obsession with small ED optics), my coalman, Graham, bought his Swarovski’s about ten years ago, and I was glad to see that they looked as though they’d been used. When I asked him why he chose them he said, “they’re supposed to give brighter views in low light.”  I thought that answer was a little vague though. He didn’t seem to know anything about the fluorite element in the objectives, or the effects of coatings on the optics. He was simply won over by the advertising. I believe this is common among buyers of high-end optics. Afterall, you don’t need to know anything about an internal combustion engine in order to drive a car do you?

Indeed, I knew far more about his Swarovski’s than he did. Nevertheless, we compared the images. I got a shot of Graham’s 8.5 x 42s and he got a chance to test out my 8 x 42 Sierra’s. The results were interesting.

I felt the image quality was excellent in the Swarovski’s. It gave a slightly more neutral colour tone to the Sierra’s in a very slightly larger true field (7.6 angular degrees). Contrast was excellent with really first-rate definition. The built-in field flattening lenses in the eyepieces improved the edge of field correction, and the slight colour fringing I had tried hard to detect in my Sierras was invisible in the Swarovski’s.

Graham liked the Sierras too though. Indeed, he said to me that, ” they’re pretty much the same aren’t they?”

I found it hard not to disagree. I felt the images were much more similar than different.

But what I did appreciate were the mechanical attributes of Graham’s binocular. Its buttery smooth focusing wheel made it easy to adjust focus distance from about 4.5 feet to infinity very swiftly; a bonus for birders I guess. I also appreciated the wonderful diopter adjustment apparatus and hearing the ‘click’ as it was turned to the correct setting.  This clever diopter locking mechanism means that there’s little chance of it slipping out of place during field use. Great, but not something I couldn’t live without.

The Swarovski’s body is a very rugged magnesium alloy chassis which gives a feeling of reassurance while handling the optic, but I didn’t really understand how it would be more resistant to corrosion over the far less expensive polycarbonate body usually found on the majority of sports optics. What Graham and I did notice was the significant weight difference between the models. The Swarovski’s were nearly 200g heavier than the Sierra’s, something that would definitely have a bearing on observing comfort during prolonged field use.

The excellent life-time warranty on the Swarovski’s was something Graham appreciated. He told me that one of the caps on the ocular lens had worn out (they can actually be removed for easy cleaning of the eye lenses) but one of the company reps immediately fitted his unit with a new one; that’s great service!

In the end, I was very grateful to Graham for bringing by his high-end binocular. I was delighted to know that there wasn’t much in it optically. But then again, I kind of expected as much! Did the experience tempt me to save and invest in a Swarovski? I’d have to say no. My Sierra’s were plenty good enough, warts and all!

What to do with the Sahara’s? My sister- and brother-in-law love the great outdoors; camping, glamping, fly fishing, hill walking and sight seeing. The’ve never owned a decent binocular so these will serve as a suitable Christmas gift for them. I just know they’ll love it and use it!

As for the Barr & Stroud Sierra binocular, I will present a separate, in depth review of this instrument in another blog.

Thanks for reading!

 

Neil English is author of several books on amateur astronomy.

 

De Fideli.

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