Main types of binoculars

MAIN TYPES OF BINOCULARS

Since Hans Lipperhey invented the telescope in 1609, this instrument and – a bit later – its two-eyed version, the binocular, has been put to good use in many areas of life. The following may be some of the main specific binocular applications that have developed over time. There is no strict separation between these different usages, many instruments in fact belong to more than one of the following categories.

  • Astronomy
    • Astronomy was one of the first applications for telescopes, and today a large number of professional and hobby astronomers use not only telescopes in various sizes of aperture, but also binoculars of very different sizes, magnifications and configurations. While you can use virtually any binocular under the night sky and see more than with your naked eyes, for sweeping the milky way and impressive starfield gazing, a large field of view, an image with well corrected aberrations, a flatfield image and exit pupils of 5mm or more are a clear advantage. If you are more interested in observing details on the moon or looking at star clusters and nebulae, a large astro binocular or even binocular telescope with exchangeable eyepieces, giving you magnifications in the range of 20x – 70x or more, may be the instrument of choice. Of course, the single eyed telescope is – for several reasons – the better choice when very high magnifications (200x or more) are used to observe details on a planet surface. The viewing and observing with two eyes, however, is much more enjoyable in the range of low to medium magnifications, giving you unforgettable impressions, e.g. “3D moonwalks”, when seeing conditions are good.
      Dedicated astro binoculars often come with individual focusing on each eyepiece, instead of a central focusing mechanism.
    • Examples of typical “astro binoculars”
      • Fujinon 10×50 FMT-SX2
      • Nikon 18×70 IF WP WF
      • APM Binocular Telescope 82mm ED APO
      • Omegon Argus 25×100 MS
      • Vixen SG 2.1×42

  • Nature Observation, Birding
    • A wide field of view, good correction of chromatic aberration, color fidelity, magnifications in the 7x – 10x range and light weight – these are some of the characteristics appreciated by birders and wildlife observers. For observations in broad daylight, objective lens diameters between 30-42mm are popular, at dawn or dusk instruments with 50mm or so provide a bit more light.
    • Examples of typical binoculars for birding and wildlife observation
      • Leica Noctivid 8×42
      • Kowa Genesis 8×33
      • Zeiss Victory SF 8×42
      • Nikon EDG 7×42
      • Swarovski EL SV 10×50

  • Hunting
    • Traditionally, hunters have preferred sturdy, armored instruments with 8x to 12x magnifications, depending on the type of hunting activity, and low light capabilities, so typically with objective lens diameters of at least 42mm, likely 50mm or more. Instruments with laser based range measurements (some with on-board ballistics calculation programs) form a segment of this market.
    • Examples of typical hunting binoculars
      • Optolyth Royal 8×56
      • Steiner Nighthunter 8×56
      • Swarovski SLC 10×56
      • Zeiss Victory HT 10×54
      • Leica Geovid 8×42 HD-R (Typ 402)

  • Military, Police, Surveillance
    • Looking at the requirements put out by armies all over the world, binoculars used for military / police tasks in general need to be sturdy, armoured, waterproof, shockproof, easy to carry around, and reliable in any environment. Most army binoculars come with individual focusing on each eyepiece. While in the past, configurations such as 6×30 or 7×30 were frequently used, more recently 8×30 or 7×40 have become the norm, for surveillance or special tasks also 10×40 or 10×50.
    • Examples of typical military binoculars
      • IOR Valdata 8×30 (Romania)
      • Kern 8×30 (Switzerland, 1960s)
      • Kern 8×30 (Switzerland, 1990s)
      • CZJ 7×40 B/GA (East Germany)
      • KOMZ BPS 10×40 Baigish (Russia)

  • Marine
    • Binoculars used on vessels or boats have to satisfy a number of requirements. First of all, they need to be fully waterproof. Then, since they are not being used on stable ground, they usually come with a relatively modest magnification, most often 7x, except for long range binoculars on the bridge of large ships where 10x may be the better choice. And finally, when you need to find a port entry at twilight you need an instrument with a large exit pupil. 7×50 or 10×70 are therefore the typical configurations of marine binoculars.
    • Examples of typical marine binoculars
      • Nikon 10×70 IF HP WP
      • Fujinon 7×50 FMT-SX2
      • Zeiss 7×50 B GA/T*
      • Steiner Commander 7×50 K
      • Minox BN 7×50 DCM

  • Pocket Binoculars
    • As the name indicates, pocket binoculars are supposed to fit into your pocket, so above all else, they have to be small. This means they feature smaller objective lenses, a smaller binocular body and usually also smaller eyepiece lenses than full-size binoculars, and they frequently are equipped with a double central hinge that allows the binocular to be folded into a narrow package. The small size comes at a price: small exit pupils can make eye placement a challenge, and the light weight leads to increased shaking. However, a small binocular that you actually carry with you on your leisure activity, at sports events or when hiking, is always better than no binocular.
    • Examples of typical pocket binoculars
      • Zeiss Victory Pocket 8×25
      • Leica Ultravid 8×20 BR
      • Kowa Genesis 8×22 Prominar
      • Nikon Sportstar EX 8×25
      • Meopta MeoSport 8×25

  • Opera Glasses
    • These are small instruments with simple optics for use at a theatre, opera house or concert hall. They are also called Galilean binoculars because they are built using Galilei’s telescope design which does not use prisms. In an instrument with small dimensions, the simple Galilean design results in a narrow field of view and low magnifications of usually no more than between 2x and 3x.
    • Example of a typical opera glass:
      • Eschenbach 2.5×27


Binocular manufacturers

CURRENT BINOCULAR MANUFACTURERS

If you use Google to identify today’s binocular manufacturers, you will get something like 150 company names. However, this result is utterly misleading. Of these roughly 150 companies, less than a dozen actually still manufacture their own binoculars; all the others are just selling binoculars under many brand names, but the instruments have been manufactured by a select few producers.

On the American continent, not one single binocular manufacturer in the proper sense of the word is left. Some few companies are today assembling binoculars from imported parts manufactured in Europe or Asia, a noteworthy example being Meopta USA, Inc. located in Hauppauge, NY, which imports entire binoculars form their Czech parent company, from which it also imports parts to assemble their MeoPro line in the USA. Other examples would be Leupold Optics in Oregon, which assembles a number of their instruments in the US, using mostly parts manufactured abroad, and Maven Optics in Wyoming. Most others have completely outsourced the production of binoculars, mostly to China, a smaller number to Japan.

In Europe (including Russia), at least the following companies are possibly still designing and manufacturing their own binoculars, or at least essential parts of some of their product lines: Docter / Noblex (Germany), Leica (Germany and Portugal), Zeiss (Germany and Hungary), Steiner (Germany), Minox [?] (Germany),  Meopta (Chech Republic), Optolyth (Germany), IOR (Romania), KOMZ (Russia), Yukon (Lithuania).

In Asia, companies producing their own binoculars, or at least essential parts, include the following Japanese entities: Canon, Fujinon, Kowa, Nikon, Olympus, Pentax, Vixen. All of those have outsourced the lower end of their product lines over the last few years to Chinese manufacturers. Beside those seven companies, Japan is home to large companies producing binoculars for third parties and sold under third party tradenames, the most important one being Kamakura, which manufactures parts and entire binoculars for leading European and American customers in the optics and outdoor businesses.
In China, the market leader is KUO (Kunming United Optics). KUO designs, manufactures and sells their own instruments, but is today also the global leader producing parts and entire binoculars for the worldwide binocular markets, lately even in the high end market segment (e.g. for astro instruments). If you buy binoculars today that are labelled “China” or “Made in China” (and you will nowadays find that label even on instruments with the prestigious blue “Zeiss” logo), there is a high chance that it has been manufactured by KUO. Some companies, such as Oberwerk of the US, source from other manufacturers in China, but do not disclose their names.

Will the entire binocular production eventually move to China? The future will tell. But with some of the famous and once prestigious European sports optics companies now owned by financial investors (with in some cases reduced investment budgets and company restructurings, including layoffs); with optics and photo shops nowadays frequently slashing their inventories and running a tight working capital figure; and with consumers now often buying their optics equipment online or from large department stores, binocular markets are expected to undergo significant changes in the future.

Where to buy binoculars

WHERE TO BUY BINOCULARS

Thirty years ago, if you were shopping for a pair of binoculars, you would either go to a photo / sports optics shop, a hunting / outdoor merchant or to some select department store which would carry this kind of device. You would normally have expected to find a decent selection of binoculars in-store and would have been able to try out some instruments on the spot.

Since then, things have changed a bit. Nowadays, the “omnipresent internet vendor named after a South American river” is the place where many would turn to in order to look up and select binoculars and related items such as tripods, bags etc. Many other internet vendors all over the world are selling huge quantities of binoculars; some of the traditional optics stores have joined the game by opening an internet presence in addition to the traditional store activities.

It is clear that this trend has changed the way we buy binoculars. Online, you either have to order an instrument, review it once it is delivered and then return it if you don’t like it, or you follow the same procedure but order several instruments at once of which you will return those that you do not intend to keep. But either way, the in-depth comparison, review and testing of a number of binoculars “in parallel” has become more difficult when buying online than when making your selection at a large optics store.
Only a very few select shops still carry a sizable stock of binoculars and thereby offer the possibility to compare and select instruments directly at the store. If they don’t carry an inventory, they will sometimes order one or a few instruments for you which you can go and review at the shop once they have arrived.

Many people follow discussions and debates about particular instruments in internet forums (see label “Further Information” on this website) and then go and review that instrument at a shop, or order one online. But what you can definitely learn from the discussion on such forums: a specific pair of binoculars may not suit your eyes, your face anatomy or your observation habits as expected even if it has received top marks by other people online or in a magazine; numerous forum posts from disappointed users give sufficient evidence of that. So remember: nothing but your own review, testing, trying out counts when buying binoculars. For those wanting to go a bit deeper in their evaluation procedure, see the next paragraph “How to Select Binoculars”.

How to select binoculars

HOW TO SELECT BINOCULARS

The following “manual” is being used by BINOCULARS TODAY to review and evaluate binocular performance. You may choose to use it, either entirely or only those parts which you consider particularly relevant for yourself, for your own binocular reviews. Only test criteria accessible to the “ordinary binocular user” are included; criteria requiring sophisticated procedures or special equipment (e.g. for measuring transmission) have not been mentioned here. Data from such measurements can sometimes be found in the reports from testing institutions (e.g. allbinos, House of Outdoor etc., see page “Further Information” on this website)

  • Review Criteria
    • GENERAL
      • External Finish, Build Quality: how well has the binocular been finished? E.g. are there gaps in the rubber armour, is the leatherette perfectly glued on, are the metal / plastic / rubber parts well joined together ?
      • Haptics: how pleasant to hold are the surface materials?
      • Grip: how well can you grab and hold the binocular under dry and wet conditions? Is the surface material sufficiently “rough” / coarse so that it doesn’t slip out of yours hands in wet environments?
      • Balance, ergonomics: is the binocular front-heavy or back-heavy, or well balanced? Does your finger rest easily on the focus wheel of a central-focus instrument, or is operating the focus mechanism uncomfortable? How about the diopter adjustment?
      • Weight: can you easily carry (esp. on strap around the neck) and hold the instrument?
      • Accessories: does the binocular come with all the usual accessories, i.e. neckstrap (how wide is it? what shape? is it soft enough?), carrying bag, objective covers, eyepiece covers? Is the bag useful or a pain to store and remove the binocular?
    • MECHANICS
      • Central hinge: too stiff or too lose, or easy to adjust but stiff enough to keep its position? What is the range of adjustment, so that people with very wide or narrow lateral eye distance can find a comfortable viewing position?
      • Eye cups: extendable? Are they of the fold up/down or screw in/out type? If the latter, are there intermediate stop clicks, and how well do they hold a chosen position? How comfortable are the eyecups on your eye sockets and nose?
      • Focus mechanism (central or individual): How fast or slow is it? How many turns to focus from near to infinity? How precisely does it operate? No play? Does the focus operate evenly and consistently? Is focusing (too) stiff, or does it turn (too) easily ? Extra travel beyond infinity: when you focus to infinity, is there some travel left (so that in case your eyesight changes over time, you still can find a sharp focus)?
      • Diopter adjustment: Does the „0“ mark correspond to a zero diopter adjustment between left and right eye, or is the mark somewhat off the true zero? How precisely does diopter adjustment operate? No play ? What is the adjustment range (should be +/- 4dpt or more)? Does the adjustment operate evenly and consistently? Is the adjustment (too) stiff or does it turn (too) easily? Can the mechanism be locked to prevent unintended adjustment?
    • OPTICS IN GENERAL
      • Inspecting the instrument from the side of the eyepieces: what is the quality of antireflection coatings? Is the exit pupil perfectly round? Any false pupils and if yes, how remote from the exit pupil? Are there other bright structures, reflections etc. around the exit pupil? How much vignetting can you detect?
      • Inspecting the instrument from the front end: quality of coatings, how intense are reflections from a light source? How well blackened and baffled are the tubes? Any bright elements causing reflections when pointing a light source into the tubes?
      • Are all lens surfaces and (as far as visible) prism surfaces in perfect condition, with no damages or impurities visible?
      • How is the “Einblickverhalten”: How easy is it to find a comfortable placement of the eyepieces against your eye sockets allowing you to easily view the entire field of view with no shadows, “kidney beaning”, or similar effects in the image?
      • Eye relief: is it sufficient (ideally 17mm or more) to use the instrument while wearing glasses?
      • Collimation / alignment: is observing easy and comfortable with no eyestrain or headache at all even after extended periods of observation?
      • Effective Aperture: is it identical with the diameter of the objectives, or is it “stopped down” to a smaller diameter and the instrument is therefore not as bright as it should be?
      • Close focus: sufficient for your needs ?
    • IMAGE QUALITY:
      • Size of the field of view?
      • Central sharpness, contrast, “brilliance” of the image (ideally, use various methods for this: test contrast by observing structured surfaces of various objects; use test sheets like USAF 1951; etc.) ?
      • Off-axis sharpness: how wide is the sweet spot? How much blurring occurs towards the edge of the image? How far out does the image stay sharp, or at least usable?
      • Distortion characteristics: pincushion distortion, barrel distortion? Is there a „globe effect”, and if yes, how strong? How comfortable is panning?
      • Chromatic aberration: are there discernible color fringes in the center of the field ? How prominent are they towards the edge of the image?
      • Stray-light: how well are reflections, veiling glare, flares etc. suppressed when observing e.g. across a glittering water surface against a low standing sun? Use several methods including natural and artificial light sources.
      • Twilight performance: observing at dusk e.g. against a dark forest while the sky is still slightly lit after sunset, does the image appear “washed out” or is image contrast still sufficient?
      • Ghosting (test on bright light sources, e.g. moon at night or streetlight): are there disturbing ghost images?
      • Flares, Spikes: how prominent are they on bright light sources at night?
      • Color fidelity: do you see any significant tint or hue when looking through the binocular “upside down”, i.e. looking through into the tubes from the objective side on a white sheet of paper? Does the image of objects appear (too) warm or (too) cool when compared to the real colors of the objects?

Some common errors and misconceptions

COMMON ERRORS AND MISPERCEPTIONS

Bill Cook’s book (see page “Further Information”, tab “Books about Binoculars”) lists dozens of misconceptions or misunderstandings about binoculars, some of which seem ineradicable in the public discussion, despite all efforts by serious binocular enthusiasts. But abandoning hope is not an option, so we would like to present our own selection of a few particularly pertinent ones here.

  • “A few years ago, I tested such-and-such Nikon binocular. Now I purchased the so-and-so Zeiss bino. It is much sharper, brighter and shows more contrast than the Nikon.”
    You sometimes read about comparisons such as the above, apparently made from memory, possibly under different lighting conditions, and observing completely different sets of objects or landscape elements with the different binoculars that are being compared.
    Not only is our memory, as we all know from experience, a tricky subject matter; people’s physiological conditions undergo changes from one day to the next and even during the day, something that affects our eyes and vision considerably. Experienced binocular users know that an impression gained of a particular instrument can change with time, so that you may prefer today a binocular over another one which you had rated higher some time ago.
    Moreover, comparing binoculars under anything else than identical conditions will almost certainly lead to errors, false assumptions and unreliable results.
    BINOCULARS TODAY never trusts comparisons of binoculars that have not been gained side-by-side! A review of several binoculars has to be undertaken simultaneously and under identical conditions, or its results will almost certainly be flawed.
  • “Eyecups need to be fully twisted up (extended) when used without spectacles, and twisted down (folded down) for spectacle wearers”
    This statement is not wrong. But it is not the full truth. The comfortable use of binoculars with extended or folded down eyecups (resp. fully or partially extended if they are of the twist-up type) depends on many factors, including: the size and shape of your eye sockets; other aspects of facial anatomy; your preference of shielding light from the side of your eyes completely off or letting it come through to some extent; the need to prevent the fogging-up of the eye lenses in humid conditions; finding the right eye placement to minimize color fringes in the image (see below, “CA”), or to avoid kidney-beaning (dark shadows at the edge of the image); etc.
    In short: there is not one single “right” method of extending or not extending eyecups. Because of this, those binoculars that not only feature twist-up eyecups instead of foldable ones, but also are fitted with intermediate click-stops between fully out and fully in, allow the user to find his or her ideal position more easily.
  • CA (chromatic aberration): “This and that binocular shows a disturbing amount of color fringing” – “I do not agree, I find the image almost free of color fringes”
    Exchanges like this are a very frequent subject of discussions in internet forums, where one forum member complains about excessive color fringes in a particular binocular, whereas other members don’t see any such fringes.
    A lot has been said and written about chromatic aberration (“CA”), one of the aberrations of an optical system which affect image quality. There are in fact two types, the so-called longitudinal chromatic aberration, which mostly manifests itself on objects in the center of the image, and the lateral chromatic aberration, which causes color fringes on off-axis objects. CA is a concern for every binocular optics designer and manufacturer; it can be much reduced, but never fully eliminated. Even the very best instruments will exhibit some color fringes in the outer parts of the field of view.
    Of course, many cheap binoculars tend to show significant color fringes even in the center of the image. In the middle to upper price range, much has been improved over the last few years. Today, even some  of the less costly instruments have decently designed optics and may even use low dispersion glass.
    But what gets often overlooked: a large part of the complaints about CA falls right back on the complaining users themselves. The reason for this is that color fringes can be triggered even in some of the best binoculars by not properly aligning your eyes to the exit pupils of the binocular.

    Please also keep in mind that some people seem much more sensitive to CA effects than others. For some, the almost total absence of color fringes in a binocular image is a must, whereas others are more tolerant.
    So the next time you wonder why some binoculars from first rate producers get criticized for bad CA correction, have a look at the binocular in question yourself before jumping to conclusions.

  • “It does not make sense to use a binocular with more than a 2-3mm exit pupil during daylight, since the diameter of your daylight adapted eye pupils will not be more than 2mm.. It also does not make sense for a 50 year old to use a 8×56 binocular with a 7mm exit pupil”
    These are again statements that are not wrong per se, but do not give the full truth. The so-called “useful exit pupil size” is a subject for endless debates, and the debates cover both day and night use of binoculars. According to some, only young people should use binoculars with exit pupils larger than 5mm; others disagree. But it’s not as “black and white” as it all seems.
    It is well known that the eye pupil contracts during the day and dilates at night. It is another well-known fact that the dark-adapted pupil diameter varies significantly with age; the average 30-year-old enjoys a 7mm dark-adapted pupil, whereas the pupil of the average 70-year-old does not open more than 5mm (there is significant individual variation, though).
    In bright daylight, the eye pupil adapts to the brightness by contracting to about a 2mm diameter or even less. So what would be the advantage of using a 8×40 or 10×50 binocular with exit pupils of 5mm? Would that not be utter waste, losing the larger part of the light transmitted through the instrument ?
    The answer is “yes and no”. It is true that the eye pupil will not let all the light from the binocular in. But on the other hand, the alignment of your narrow eye pupils with the larger exit pupis of the binocular is much easier than if the exit pupil was also 2mm only. That is a factor which often overlooked, but experienced binocular
    users are well aware of it.
    At night, things are a bit different. Large exit pupils of e.g. 7mm, which are the result of binocular configurations such as  7×50, 8×56 or 10×70, go often hand in hand with a sky background that is not as dark as would be ideal for observing faint DSOs. Depending on nightsky conditions and light pollution around you, a 10×50 or 7×35 (5mm exit pupil in both cases) may be the better choice, especially if your eye pupils don’t open more than 5mm (if they do, it depends on the darkness of the sky background whether or not a 7×50 or a 10×50 is more ideal).
    So, to sum it all up, the subject of the “useful exit pupil size” is a bit more complex than it appears at first glance.
    The following is BINOCULAR TODAY’s position: during the day, when there is plenty of light, an exit pupil larger than the eye pupil adds viewing comfort; experienced birders sometimes confirm that picking up a bino to spot a moving bird and placing the eye behind the eyepiece is often somewhat easier with an “oversized” exit pupil. At night, however, all light that is not taken in by the eye pupil is basically lost, and since light is scarce at night, the exit pupil should not be much larger than the eye pupil.
  • “I can easily hold a 20×80 binocular by hand for my observations of the night sky”
    The proper answer to such statement would be: “I bet you can, but do you know that when handholding it, you will see less in your 20x binocular than you would see in a 10x binocular mounted on tripod?”
    Fact is: every binocular of any size will show you more detail when mounted on tripod than when you observe holding it by hand. Even a 6x or 7x instrument will give you greatly enhanced detail recognition if you mount it on a tripod. The reason is muscular tremble or shake, which is different from person to person, but never totally absent.
    The higher the magnification, the larger the difference of the so-called “binocular efficiency” between handheld and mounted. The formula for this is
  • Ehandheld = Emounted / (1+0.05M) where M is the magnification.
    Using this formula, you will see that you lose about 30-40 percent of your instrument’s potential if you use it handheld instead of mounted.

    Of course, for several reasons mounting may not always be your preferred solution. A possible alternative (of sorts): using one of the image-stabilized binocular which you find on the market in various configurations and prices.

    But last not least: when on a hike or otherwise on the run, there may not be an observation method other than handheld, so use it fully – and enjoy your binoculars thoroughly! Even handheld observations can be addictive.

  • “A 10×30 shows more than a 8×40”
    Right or wrong ? The correct answer is: it depends.
    During  broad daylight, you will see more detail in the image of the 10×30 than in the 8×40, due to the higher magnification. The higher brightness / larger exit pupil of the 8×40 does not help here because your eye pupils will be contracted.
    At dawn or dusk, things will be the other way around. With your eye pupils dilated to 5mm or more, the 8×40 will be brighter and let you see more than the 10×30 with its 3mm exit pupil.
    Another example: compare an 8×30 with an 8×40. During the day, not much difference. At night, you will be better off with the 8×40.
    Of course, this all assumes similar optical quality of the instruments compared, and it does not take into account muscular tremble/shake of your hands that will affect performance of a higher magnification binocular more than lower magnification.
  • “The best binoculars are made by Leica”
    Statements like this, naming a particular brand „best binocular“, can be heard in discussions among binocular enthusiasts as well as in many other places. But: they don’t really make sense!
    Of course, the technical quality of a particular device can be described perfectly well, so the type of glass used for the lenses and prisms, the coating applied to the optical surfaces, the material used for the body of the instrument, and many other specifications are of importance when evaluating binoculars. Such evaluation can show that one specific instrument is built using better materials and higher standards than another one. However, whether a specific pair of binoculars will „perform better“ than others in the hands of an individual is hard to predict, since the eye apparatus and face anatomy varies quite significantly from person to person, and the same holds true for differences in perception (color, structures, etc). Therefore, recommendations given by colleagues or friends are definitely useful and helpful, but nothing can replace the personal checking and testing of an instrument!
    A top of the range binocular will most likely satisfy the discriminating birder or astronomer more than a cheap low quality instrument. Nevertheless, there simply is no such thing as “the best binocular”.
  • “My binoculars are extremely sharp from edge to edge” Off-axis or Edge Sharpness – a holy cow for some, a much overrated hype for others.
    Knowledgeable experts such as William J. Cook have devised methods to measure edge sharpness (see his book under “Further Information”, Tab “Books about Binoculars, p.50 ss.). But how important is off-axis sharpness in practice (compared to, e.g., off-axis illumination)? Here are a few thoughts about the subject.

    Hobby astronomers may give a different answer here than birders. To sweep the nightsky and observing starfields with stars shown as sharp tiny dots right to the edge of the image is of course more satisfactory than having the outer 30% of the image filled with blurred white spots. This is especially true when the instrument is mounted so that you sometimes just let your eyes wander across the field of view with the instrument held still. However, if the object of observation is Jupiter or Saturn, and the astronomer uses only the central part of the image, some edge blurring may be acceptable.

    For the birder, things may look different. Since the human eye does only see a sharp image at one central spot at a time, only the center of the image needs to be really sharp, and to follow a flock of birds with the binocular it is sufficient if the outer parts of the image are somewhat sharp and the birder can re-center the instrument to the respective bird he or she wants to observe. On the other hand, in more static conditions, the birder may have a large binocular mounted and would then prefer the image to be really sharp over most of the field of view.

    Making the image of a binocular sharp to the edge of the field is easier for binoculars with a narrow field of view than for wide-field binos. Often, when edge sharpness is compared between different instruments, this factor is overlooked. The wider the field of view, the more difficult it is for the optics designer to keep the image sharp in its outer areas. To succeed, additional or more sophisticated optical elements have to be used which usually make the instrument larger, heavier and more expensive, something that does not go well with the common demands for lighter binoculars (demands which need to be questioned for other reasons). Binoculars with an unusually wide field of view and at the same time an extraordinary edge sharpness such as the new Nikon WX, coming in versions of 7×50 and 10×50, are big, heavy beasts, barely usable without a tripod, and cost several thousand Euros. Calls for the same performance in a much lighter, smaller and cheaper package are equivalent to demanding of optics designers to overcome the laws of physics.

    But even the very best of the best instruments will not exhibit a 100% perfect edge sharpness (as they will not be 100% perfectly corrected for chromatic aberration). Most binoculars, even the very good ones, show a varying degree of edge blurriness. The initial statement about “extreme sharpness from edge to edge” is hardly ever true in practice, and some people making such claims don’t really know what edge sharpness really looks like.

  • “I don’t need a premium binocular that costs 2000 dollars and more. I found a very good pair of binoculars at my department store for just 75 dollars that are every bit as sharp, bright and well built as any premium binocular”
    You will frequently encounter statements like this when browsing internet forums. Usually, they are immediately dismissed by some well-meaning forum colleague who goes to prove at length that in optical instruments like in any other precision devices, you normally get what you pay for, so the statement must be false.
    I have a friend who in a blind testing of wines can distinguish between a 2013 and a 2014 Amarone. I would have no chance doing that; my taste buds are just not that finely tuned. Without looking at the label, I cannot even say for sure whether a certain wine is Italian or Spanish.
    On the other hand, my eyes are relatively sharp, and many years of experience with selecting, testing and comparing binoculars have taught me to spot differences between good, very good and outstanding binoculars with some certainty (not to mention differences against the not so good instruments).
    Maybe my wine expert friend would fail at binocular comparisons, like I fail at his wine testing events, and perhaps he would find the 75 dollar binocular as sharp and bright as a premium instrument.
    Objectively, the probability that a cheap binocular is “every bit as good” – in terms of transmission, sharpness, brightness, correction of aberrations, build quality etc. – as the very expensive instruments from renowned producers is virtually zero. Certain specifications, such as e.g. transmission, can be measured, and they will prove that most often, the performance of an expensive binocular will be better than that of any cheap one. However, it is a totally different story whether users will be capable of spotting the differences with their eyes; if they can’t, you need to decide for yourself whether you rather pity them for not seeing the difference, or whether you envy them because they don’t have to buy expensive binoculars like some of us to be happy.
  • «If you want to do serious birding, only the top glasses from Swarovski, Zeiss or Leica will do. They allow you to perform difficult identification jobs under critical viewing conditions which you would fail with binoculars from other manufacturers.”
    A bit of skepticism is appropriate here. First, it is of course true that with a modern glass from a top manufacturer (you would have to include Nikon here), you may be better equipped than with many binoculars from less reputable brands. On the other hand, there are now many excellent binoculars with brand-names such as Meopta, Kowa, Hawke, Kite, Maven, Vortex and others which are in use with birders all over the globe. I have yet to meet an ornithologist or other wildlife observer who credibly tells me that he failed to identify a rare bird with his Pentax, Olympus, Kahles or Bushnell glass but would have been able to succed with the identification if only he had a Victory SF, Ultravid HD or EL SV available. These premium glasses may perhaps be more fun (and definitely more prestige!) to use than some cheaper binocular, but the performance gap between premium and upper middle-class is much less obvious today than many assume.
  • “For birders, perfect color fidelity is an absolute must in a binocular. Even slight hues or tints, e.g. a slightly yellow color tone, may make it impossible to correctly identify a species”
    While it is true that color fidelity is important and useful in birding binoculars, it is on the other hand a fact that image colors out in the fields change much more with changing lighting conditions, e.g. between sunny and overcast, than with binoculars that exhibit a shade of color, e.g. a slightly warm tone, or a slightly greenish tint. As we all can tell from experience, the human eye compensates for quite a bit of the color “infidelity” when we wear sunglasses. Of course, there is a limit to that. But the slight color tones exhibited by many modern quality binoculars do not affect the birding job as much as has sometimes been reported.

Definitions and Terms

Binocular and Optics Terms and Definitions

Many books contain an appendix with an index of terms.
One of the most useful reference works to look up definitions and terms for English speaking readers is the “Field Guide to Binoculars and Scopes”.

For German speaking readers, the book “Handferngläser” by Holger Merlitz provides solid and thorough information about all important terms used in the binoculars trade.

Both books are listed on this website on the page “Further Information”, under the tab “Books about Binoculars”.

Below are “unofficial” translations of the Index at the end of Holger Merlitz’ book “Handferngläser”, second edition 2019 (the numbers next to each term indicate the page numbers in the book where the respective terms are discussed).

Just click on “D-E” or “E-D” to open pdf files with the translated terms.

E-D     D-E

The following are a few important abbreviations frequently used when discussing binoculars and their characteristics and performance:

AFOV   =  Apparent field of view
AOV      =  Angle of view
AR         =  Antireflection (coating)
CA         =  Chromatic aberration
CF         =  Central focusing
EP         =  Exit pupil
ER         =  Eye relief
FOV      =  Field of view
IF          =  Individual focusing
IPD       =  Interpupillary distance
M          =  Magnification
MTF     =  Modulation transfer function
RFOV   =  Real field of view
TIR = Total internal reflection