Sorting the Wheat from the Chaff: Small Touches that Make a Good Binocular Great.

Binoculars under test, clockwise from top left; The Barr & Stroud Savannah 8 x 42, the Barr & Stroud Sierra 10 x 50, the Pentax DCF 9 x 28, the Celestron Nature DX 8x 25 and the Opticron Aspheric LE 8x 25.

Not all binoculars are created equal. Some match the advertisement claims, while others do not. In this blog, I’ll be exploring optical and mechanical features that I like in a hard-working binocular and whether or not the price paid for a binocular matches its performance in the field.

Coatings & Baffles:

Okeydokey. Let’s get started.

The reader will note that all the binoculars (featured above) are meant to be fully multi-coated. Here is what I understand the term to mean:

All glass surfaces have multiple coatings and it is the best kind, resulting in light transmission of 90-95% for bright, sharp and contrast images.

Source here.


In the first investigation, I performed a bright light experiment to test for;

1. On-axis ghost images which is a sensitive test of the quality of the anti-reflection coatings applied to the optical components within the binoculars.

2. Off axis flaring which tests how good light baffling works in the instruments.

The light source needs to be small and as bright as possible. For this, I elected to use the torch on my iphone with the setting set to maximum. The ambient light was dimmed by pulling my living room curtains in such a way as to leave a small amount of daylilight to illuminate background objects. As well as looking for on-axis reflections and off-axis flare, I studied how well defined the images were immediately behind(backlit) and around the light source.

Performing a small, bright light test in the comfort of my living room. Note the small amount of daylight left in the room to assist imaging backlit objects around the light source(my iphone torch). Note the tiny reflection from the iphone camera lens itself near the centre of the picture.

All the binoculars can be sharply focused at the close distance chosen for the test(~3 metres) and all the images were performed at the position of sharpest focus.The experiment was performed using both eyes separately to check that the effects noted were in any way dependent upon the eye barrel used.

To quantify the effects I chose a number scheme from 1 through 10, with 1 representing very poor perfomance and 10 being sensibly perfect. It must be noted that no binocular, no matter how well appointed, can achieve a 10 score. Even the very best instruments display some degree of unwanted internal reflection and/or off axis flaring. Thus, to expect none at all is quite an unreasonable proposition.


Instrument                           On-axis internal reflections               Off-axis flaring

Nature DX                                               2                                                  4

Pentax DCF                                            5                                                  6

Opticron Aspheric LE                             4                                                  5

B&S Sierra                                              8                                                 8

B&S Savannah                                        8                                                 9



No significant differences between the left and right barrels were uncovered. The results documented are thus representatve for both eyes.

All the binoculars gave acceptable results with the exception of the Celestron Nature DX. The on-axis internal reflections were very strong and bright, with some reflections taking up quite a bit of the field of view. This made imaging backlit objects very difficult. If this is a fully multi-coated binocular then my name is Mickey Mouse. Off-axis flaring was also the strongest in this unit.

To my suprise, the Opticron proved less effective than I had expected with a few fairly prominent reflections on-axis but noticeably better off-axis performance. It was overall however, in a different league to the performance exhibited by the Celestron unit.

The Pentax also suprised me as I expected it to have the best performance, based solely on its reputation for quality and the not inconsiderable price I paid for the unit. It displayed one bright, unwanted reflection on-axis, but had improved off-axis performance in comparison to the Opticron unit. In addition, the definition of backlit objects was considerably improved in both the Pentax and Opticron units over the Celestron.

To my surprise and delight, both the Barr & Stroud Sierra 10 x 50 and the 8 x 42 Savannah showed much more subdued on-axis reflections than the Opticron and Pentax. Instead of bright spots, both these binoculars gave very much more subdued reflections. They were certainly present but with far lower intensity. Off-axis performance was also very impressive, with the nod going to the Savannah. Backlit definition was also excellent in both these instruments. The reader will also note that larger aperture instruments collect more light and so might be expected to have more on-axis internal reflections and off-axis flaring than the smaller aperture binoculars tested. That this was not found to be the case in both the Barr & Stroud units was quite remarkable!

Conclusions: Buyers should be wary of marketing claims.  The Celestron Nature DX clearly has inferior coatings to the other instruments tested and is certainly not fully multi-coated in the same way as all the other units were. This is in keeping with its low price(the lowest of all the instruments tested) and could be said to be an acceptable tradeoff owing to its very low street value (£59 paid). Still the result is rather worrying, as I would reasonably expect the larger DX models to be manufactured in much the same way, and so they may have undergone the same shortcuts somewhere in their construction. Any owners of larger Nature DX binoculars need to check(don’t go all proud on me!) this out and report to the amateur community.

Considering the price paid for both the Barr & Stroud units was about the same as the Pentax binocular(in fact, the Savannah, which I purchased secondhand cost me significantly less), I feel they both offer excellent protection against internal reflections and are very well baffled. Whoever made these units knew what they were doing and properly executed the technologies available to them.

So you don’t always get what you pay for.

Caveat Emptor!

A general note on on coating tests: If you’re a binocular collector, why not perform your own set of tests on them to see if they show evidence of sub-standard anti-reflection coatings? I would expect older models to fare worse in such tests e.g. vintage binoculars made in the post-war era and the like.

A general note on baffling: It occurred to me that while baffling is an important design feature in a good binocular, it is possible to over do it. A well baffled instrument produces images that are richer in contrast than an instrument with inadequate baffling, all other things being equal. But manufacturers can deliberately over baffle the light path with the aim of maximising the punch of an image, but at the expense of cutting off a little too much light and thereby restricting its effective aperture. This may go some way to explaining why some models in the same price range can display significantly different images, some over-emphasing baffling to generate the maximum contrast but where the images are a tad dimmer, and those that produce brighter images but with less aggressive baffling. Since many birders use their binoculars during daylight hours, an aggressively baffled instrument may be judged as having higher contrast, but during more critical testing during low-light conditions or viewing the night sky, its restricted aperture may become more noticeable.

The effects of recess depth in binocular objective lenses: Small design features can make meaningful differences to the quality of the images garnered by a binocular. In this section, I would like to discuss the importance of having objective lenses recessed from the front of the instrument in order to minimise the effects of stray light entering the optical train during bright, daylight operations.

What I’m effectively talking about here is what a lens shade or hood does. The function of such a device is to reduce lens flare comng from the peripheral field as illustrated below for a camera lens;

Scheme of a lens with lens flare. A lens hood is designed so that it does not block the angle of view of the lens. Lens hoods block the Sun or other light source(s) to prevent glare and lens flare. Image credit: Wiki Commons.

It also doubles up to provide some protection of the object glass during adverse weather conditions, such as occurs in rain, mist and when side winds bring air-borne dust and other materials with them.

For the sake of brevity, I will only illustrate the two extremes in the binoculars discussed here. First take a look at the very deeply recessed lenses on the Barr & Stroud Savannah. It measures 7mm!

Note the very deeply recessed objective lenses in the Barr & Stroud Savannah binocular, measured to be 7mm.

Contrast this to that found in the Celestron Nature DX binocular, which had a measured recess of just 3mm.

The very shallow recess of the Nature DX objective lenses (3mm).

For the record, the others fared as folllows;

Barr & Stroud Sierra: 5mm

Pentax DCF: 4mm

Opticron Aspheric LE: 4mm

It is the opinion of this author that having a reasonably functioning lens shade does improve image contrast in daylight images, especially when viewing under bright, sunlit conditions. I was very glad to see that the Barr & Stroud instruments were, yet again, well appointed in this regard. It’s yet another small touch that will be appreciated by an avid binocular enthusiast.

The importance of good quality eyecups: Good eyecups make for comfortable, immersive binocular viewing. If too flimsily made, they can be uncomfortable to set your eyes against, or fall out of position when twisted up. For me, there is nothing more frustrating than to have to readjust the eye cups on the fly while making observations. Cheaper models invariably come with crudely made plastic cups that quickly lose their rigidity after a few weeks of hard use. Better made eyecups usually come in the form of metal-over rubber and can be set to a variety of positions that hold there, even when a little pressure is applied to them, either by touching them with your fingers or pressing your eye up to them when conducting an observation.

Of the binoculars considered here, three are particularly worthy of a few words; the Pentax DCF, the Barr & Stroud Sierra and Savannah.

The Pentax DCF has good quality eyecups. They provide the user with a choice of four positions and so can accommodate virtually anyone, either without glasses or with them on. They also stay in place when pressure is applied to them. My only gripe is that they they do have a bit of play in them and could be a bit more rigid.

The Pentax DCF has well-made metal-over rubber eyecups that off four positions, from fully retracted to fully extended. Here they are shown in the second position, midway between the maximum and minimum positions that user can choose from.

The Barr & Stroud Sierra and Savannah have significantly different eyecups as the photo below reveals:

The Barr & Stroud Sierra(left) and Savannah(right) have different eyecups, with the latter being smaller and considerably more rigid than the former.

Both use metal-over rubber. Those found on the Sierra model are typical of what you’d find on a mid-priced binocular of this size. The eyecups click nicely into place, offering three positions for optimal eye relief. They are sufficiently well made to last indefinitely if properly cared for. That said, once again, the Savannah really surprised me! Specifically, the eye cups are far more rigid than in the Sierra and click into place with a commanding “kathud” sound. What I found remarkable is that there is very little play to to be had with them. Once clicked into place, they stay in place. You’ll never have to worry about them slipping out of position while using the instrument.

What does this buy you?

Peace of mind!

Now, I’m not saying that the quality of the eyecups on the Savannah is in the same league as those beauties made by Leica and Swarovski( I recently enjoyed the use of the 8.5 x 42 Swarovski ELs), for example, which are works of art, both mechanically and ergonomically, but I doubt anyone would be unimpresed by such high quality eyecups on the Savannah. Indeed, you simply won’t see this kind of quality on any mid-priced binocular that I know of. They are dependable, rigidly set, and a joy to use in the field.

The eyecups on premium model binoculars such as the Swarovski 8.5 x 42 ELs are a mechanical marvel.

The wonderful quality of the twist up eyecups found on the Barr & Stroud Savannah  8 x 42 binocular: they just work well, with zero play and no fuss.


Thoughts on Dioptre Adjustment:

A typical position for the dioptre adjuster in many entry-level and mid-priced binoculars. It is usually found under the right eyepiece and is adjusted by twisting it clockwise or anti-clockwise, as appropriate.

Most roof prism binoculars have their dioptre adjustment setting under the right ocular lens. It usually involves twisting a ring either clockwise or anti-clockwise, as appropriate, until both eyes show a perfectly sharp image. This works very well indeed, but some dioptre adjutsment rings are either too stiff or too loose, with the result that tweaking it and maintaining its precise positioning can be problematical. High-end, premium models such as those made by Leica and Swarovski cater especially well for the individual in that one can lock in the correct dioptre position by pushing the focuser forward, dialling in the correct dioptre setting, and then pushing the focusing knob back into place, thereby settin it permanently. This is ideal and a very clever mechanical solution.

The Barr & Stroud Savannah binocular uses a very different strategy however, by placing the dioptre adjustment on a dial just ahead of the focusing wheel as shown below:

The Barr & Stroud 8 x 42 Savannah has its dioptre adjustment setting immediately ahead of the focuser. It adjusts the position of the right barrel optics.

As I explained in a previous blog, I find myself tweaking the dioptre setting fairly frequently and I have elected to do this by using bright stars in the night sky rather than using a terrestrial target. The reason I do so is that I have found that bright daylight targets present an overwhelming amount of visual information to the eye and though you can usually get very close to perfect, I have found small but consistent discrepancies between the position I chose by day and where it is adjusted to at night. Focusing on a bright point source such as a star yields an easy way to remove that ambiguity. I simply look for the tiniest, brightest star images the right barrel can provide.This has become my default custom when using the instrument for star gazing.

But doing this using a dioptre adjusting ring positioned immediately under the right ocular can be a little awkward and sometimes a bit frustrating, especially if the dioptre ring is stiff. In contrast, it is very easy to move my finger forward just a little to adjust the dioptre setting on the Savannah unit, allowing very precise tweaking of the dioptre setting to be made. I think this is a very well thought-out design feature on the Savannah that is not found on many other models.

A Strong Bridge: The design of the bridge mounting the two barrels of the binocular also has an impact on how well it operates in the field. Specifically, if the hinge is too loose, you will have to readjust the IPD every time you use it; not a deal breaker in its own right, but slightly inconvenient. Much better is a binocular that holds its IPD precisely from viewing session to viewing session. The Nature DX is quite stiff, as are the Barr & Stroud instruments, but the Pentax DCF and Opticron units are a bit too loosely mounted in my opinion.

The Savannah binocular in particular, has a very strong bridge, such that I have never needed to readjust it when it is taken out of its case. And when you consider that I’ve literally done this hundreds of times since I acquired in the autumn of 2018, I’d say that’s pretty good going! No faffing about, just remove from case, remove the lens caps and you’re good to go!

The value of a good carry strap: The carrying straps that come with many binoculars( even some mid- to high-end models) are of poor general quality. They’re usually made of poor quality plastic-based materials and fray easily. Having a good quality, padded strap  is a far better option going forward, as the more comfortable the strap, the more you’ll likely use your binocular. In addition, cheap straps cut into your skin more and in hot weather can even cause heat rash and some blistering. One of the first things I’d recommend in upgrading a binocular is to invest in a more durable, high-quality strap.

The straps that come with all of the binoculars I have discussed, with the exception of the Barr & Stroud Savannah, are of generally poor quality and could well do with upgrades. This is something I hope to do remedy over the coming months. The Savannah comes with a nice, padded strap that is very comfortable to use and will not come apart in rough field use. It was a standard accessory with the binocular; complete with the Barr & Stroud logo; a nice touch for sure and something that can only be appreciated by using the instrument for prolonged lengths of time.

A quality carry strap is an important feature if comfort is held as a premium.

Recommending an all-purpose binocular to the masses: We’ve now reached the end of this blog and it’s an appropriate time to reflect on what a quality binocular should behave like. As you can gather, I am very enthusiastic about the Barr & Stroud Savannah in particular, as a full-featured instrument that includes a lot of nice touches but at a price that won’t leave you short of breath(it retails in the region of £120-140 UK). Optically excellent(with a whopping field of view of 143m@1000m or an 8.2 degree field), water proof, and built like a tank (it tips the scales at 810g) with a 10 year warranty, the company has clearly gone well beyond the call of duty to deliver a high quality instrument that will stand the test of time. Indeed, I was so enthusiastic about this particular unit that I ventured onto the vulgar forums to give my vote to it and also to sing a wee tune:

Oh I do like to be beside the seaside

Oh I do like to be beside the sea….

Oh I do like to stroll along the prom prom prom

Where the brass band plays


I also suggested there that someone else put this binocular to the test; someone honest and experienced that doesn’t hold grudges against other people.

If that’s YOU,  then you’re in for a pleasant surprise!


Neil English was born at an early age and is Professor Emeritus of Tomfoolery from the University of Life.

De Fideli.

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