Binoculars for nature-watchers: an introductory guide

Authors: Ravi Kailas & Ganesh KR (ficustours@gmail.com)

The sheer pleasure of observing nature through a pair of fine binoculars is pretty near unparalleled, a feeling akin to the extension of your own vision, only more vivid and magnified several fold, placing you in the midst of the occupants of the distant scene. Binoculars have been indispensable tools for nature watchers (we can’t think of walking into a natural area without a pair around our necks, unless it hangs off a harness!), birdwatchers especially, for decades now. However, with the advent of digital photography, the recent generation of nature observers have reduced binoculars to mere tools of identification trading off the pleasure of the view through them against their extra weight/cost and relying instead on the ‘lifeless’ digital image for their appreciation of scene (or for identifying the subject). This article, while making a case for including binoculars in your packing list (not at the cost of a camera, necessarily!) for your next nature outing, is intended as a guide to selecting a pair, given the confounding number of variables to take into account, just in case you are (wisely) considering a purchase already and don’t know where to start. 

Criteria that (should) matter

OpticalPhysicalEconomicTypes of Binoculars
Magnification

Brightness

Field/Angle of View

Minimum Focussing Distance

Sharpness

Resolution/Contrast/Colour

Chromatic Aberration 
Eye-relief

Size and Weight

Weatherproofing/Build Quality 
Price

Availability and Service 
Basic Types   
Porro Prism   

Roof Prism

Specialist Binoculars   

Range Finder   

Image Stabilised   

Individual and   
Hands Free              Focus         

Marine
In a Nutshell

Optical*

Our eyes are remarkably versatile organs, capable of discerning subtleties of light that other optical aids will struggle to match. Ideally, binoculars should enhance (and not subdue) the refinement of our natural vision. Introducing below some of the important optical criteria to look for in binoculars 

Magnification

Simply put, the number of times closer that a particular object, located at a given distance, appears, while looking through binoculars in comparison to the naked eye. In binoculars one would see this denoted as a number (for example “10”) followed by an “x”. If, for example, it says 10x, then the object will appear 10 times nearer than it would with the naked eye, all else being equal.  

While absolute magnification is one of the key reasons one would buy a pair of binoculars, it does come with a host of trade-offs (such as brightness, stability and field of view – discussed in relevant sections in the article). For nature enthusiasts observing Earthly denizens, one could look at anywhere between 7x to 10x for handheld use (the higher the magnification the more difficult to get a steady image). Typically, for larger mammals and even birds in forested habitats (where trees limit the distance of clear line of sight), lower magnification (up to 8x) will be desirable. For subjects like shorebirds/waterfowl, one should ideally choose higher magnification (10x is a good starting point). If you are an astronomy enthusiast, you would be happier with 10x to 12x for handheld use (but other factors such as brightness and stability will also come into the picture). What you eventually choose, however, should be based on your primary interests as above, but 8x upto 10x tend to be great all-rounders. 

Details on Magnification (8x), Objective Size (42mm) and Angle of View (8.3°) as seen on the focussing wheel
Brightness

Possibly the most significant attribute for nature watchers. All else being equal, the limit to your binocular’s brightness is the of the size (denoted as a number, measured in mm, following the magnification) of the objective lenses (see image below), which determines the absolute amount of light that can be gathered by the device), divided by magnification. For example, if you are using a 10x50mm binoculars (10 times magnification and 50mm objective lens size), then this number is 5mm, which is the aperture, also called exit pupil (see second image below), through which the light from the binoculars enters yours eyes. One key factor to consider here is that the maximum dilation of the human pupil, which is around 8mm. As such any exit pupil larger than 8mm for example, while not unnecessary (as it results in a more wholesome viewing circle), does not add any additional brightness to the view. Brightness in binoculars is also determined by quality of the glass, lens coatings* etc, about which the author writing this bit of text is not bright enough to discuss in-depth, except that generally, there is a direct relationship between price and such stellar qualities that determine the ability of the bins to eke out the living daylight out of any light. 

Objective lens illustration
Showing the exit pupil, in this case with a diameter of 4.2mm, of a 10x42mm binoculars

Inevitably, nature-watchers will be faced with situations where light is a limiting factor. The main trade-offs to accessing more (magnified versions of light) are price, size/weight and magnification. Generally, for forest viewing it would be great to have a minimum exit pupil of 4mm (so 8×32 or 10×40 can be starting point), for those inevitable dawn/dusk/flashlight observation efforts, looking at owls, wild cats etc. If you are out looking for shorebirds for example, you might prefer to go with higher magnification at the cost of losing some brightness, since light is unlikely to be a limiting factor (however low contrast in flat grey conditions will be). For astronomy, please go with as bright as you possibly can (and you might want to be able to mount it on a tripod – so look for that option when you are buying for this purpose). All else being equal, brighter binoculars are inevitably bulkier (and heavier), given brightness is limited by the size of the objectives – a significant consideration for nature-watchers, who sometimes have to hike miles/long hours, and generally prefer, like most of the non-nature-watching members of the species, a life minus pains in the neck etc.  Once again ideal all-rounders tend fall somewhere in the middle, and 8×32 to 10×42 seem to be the best compromise between magnification and brightness for nature-watchers. 

Field/Angle of View

A related attribute to magnification is the field/angle of view, which is essentially how wide you can see through the binoculars (expressed as width or an angle) at a given distance. 

Generally a wider view is desirable for nature watchers – for example while observing fast moving subjects, like birds, or if you like to put the subject in the context of its wider environment – and most ‘good’ binoculars will provide an adequate field of view starting at around 6◦. However, lower end binoculars (even with identical magnification and objective lens specs) will often provide a ‘tunnel’ like view (rather than an encompassing, large image circle), of less than desirable coverage – a circumstance where the subtle differences in field/angle of view of competing binoculars, can be a significant variable for your purchase decision. 

Minimum Focusing Distance

A significant variable for those looking to focus up-close (less than 10ft are normally considered close-focusing). Those interested in butterflies, moths, dragonflies and the like will appreciate a close focusing ability of their binoculars. 

Other (optical) considerations

The optical considerations for above can be easily researched (for a purchase decision) from the specifications, which should tell all, by and large. However, the attributes below, will be best appreciated if you actually had a pair in hand (hopefully, one would be lucky enough to field-test or at least store test, these characteristics, before buying)

Sharpness

A key attribute where a clear, blur free image results in an enjoyable, strain free viewing experience. However, this goes beyond mere pleasure, as identification of subjects, with the aid of binoculars, is often a basic requirement for nature-watchers.  Another aspect to consider here is the centre to ‘edge’ sharpness, which is essentially how the sharpness varies from the centre (where it is sharpest, normally) of the image circle as you move away from It towards to circumference of the image. 

Resolution/Contrast/Colour

These are very important criteria, especially in challenging lighting conditions, for example while looking at dull coloured waders in ‘grey’ conditions, to eke out the faint details further subdued in poor lighting conditions or trying to notice finer details of a faint celestial object. Different binoculars also tend to have a background colour bias, from cool to warm, but these tend to be less obvious in better quality optics (which tend towards ideally neutral). 

Chromatic Aberration

An optical artefact that results in unnatural colour fringing around the subject, especially when viewed against the light. This can be glaringly distracting when you are looking to appreciate the finer details of the subject. Almost all binoculars have some at least, in the severest of lighting conditions, but high-quality binoculars control this coloured view better. 

*Many of the above-mentioned optical attributes are dependent on the quality of the optics and positively enhanced by lens/prism coatings, which reduce reflection of light off the lenses, thus improving the quantum/quality of light effectively reaching the final view, from the multiple layers of glass that make up a pair of binoculars. The type of coatings used can significantly alter the optical characteristics of binoculars – another basis for comparison when choosing binoculars within a similar price/specs range.

Physical

Eye-relief

The optimal distance from the eyes to the eyepiece, where the full image circle is still retained without ‘effort’. This is especially relevant for eye-glass wearers since the minimum distance from eyepiece to eyes, is greater than while looking with the naked eyes. Generally, however, due to the quirks of optical engineering, greater eye-relief (where a broader range of the optimal distance is built in) normally results in a smaller field of view. 

Size and Weight 

An important, physical criteria, since nature-watchers often spend hours on end outdoors and would appreciate a fine balance between bulk/weight they lug around and the optical qualities of their binoculars. All else being equal, higher-powered, large aperture binoculars will be bulkier/heavier, and one has to decide, based on their needs, how far down this rung they would like to descend, for their specific purpose. Another consideration here is the type of binoculars  – Porro prism binoculars are generally bulkier for a given specification than roof prism binoculars, but also tend to be priced lower, all else being equal (to add to the already confounding purchase decision)

Once again ideal all-rounders tend fall somewhere in the middle, and 8×32 to 10×42 seem to be the best compromise between magnification/brightness and size/weight as relevant to a broad spectrum of nature-watchers

The ‘built like a tank’ Swarovski 10×42 SLC. This pair has survived several interactions with rocks and hard places, and come out unscathed 
Weatherproofing/Build Quality

The ability of binoculars to withstand rain (and all associated elements of moisture), dust and a few tumbles on slushy ground (or even hard rock) is critically important for nature-watchers (especially the terrestrially fixated kind). Accidents due to impact/moisture can render your binoculars unusable when you are in the field, while you are typically miles away from anywhere where you can rectify the situation. It would be wise to pay a little more for these attributes, which will likely result in a longer lasting (resulting in lower average cost of ownership overtime) and happier relationship with your binoculars.  

Economic

Price

Price is the obvious economic consideration and limits your choices to within a range of your budget. However, generally speaking (although the gap is narrowing), the more you pay for it, the better the quality of the binoculars – and as binoculars are potentially long-serving companions (low obsolescence), you might also want to consider buying a product at a higher price level which could end up with your cost of ownership being lower over time (unless you are the type the misplaces items more than an average person does or have a tendency to get mugged for your belongings in forests etc.).

Warranty/customer service normally goes hand-in-hand with price and some of the higher-end binoculars manufacturers provide outstanding warranty terms (such as no-fault warranty, valid at least for several years, even lifetime), which should pretty much allow you to bash about your binoculars in a fit of rage and the manufacturer will still repair/replace them free of cost), and, customer service (we have had splendid experiences, especially with Svarowski Optik, as also with Zeiss and Nikon). This also feeds back into the cost of ownership over time.  

Availability and Service

While one might sit on a remote pacific island and drool at prospect of owning binoculars that catch their fancy on the (frustratingly unreliable) internet, ogling at pictures and reviews online, the chances of getting their hands on one are pretty remote. Living in a big city in India, as we do, prospects to own binoculars of your choice are pretty good (at least, they were, pre-Covid), but most models that are sold in the US or Western Europe are not available here off-the-shelf (so no chance of getting your hands on most, to test, before buying one). You could still have them imported, if you can justify the price of shipping and hideous import duties (that is, in case, you cant slip it past a sleepy customs via someone visiting from where the bins are sold)

Ok, now you have what you want in your hands. But what if something goes wrong and you want to get it repaired (regardless of warranty and on that note, warranty terms can be country specific). This is where it gets even tougher, since most of the proficient service centres are located only in their main markets (so if you live the US or Western Europe, you are generally ok). At the very least, it would help if the brand has a service centre in your place of residence, saving you typically expensive shipping costs and other customs related paperwork, to have repairs done. Having said the above, good quality binoculars seldom need any attention (unless you are unlucky and drop them awkwardly or you end up with a pair that has a manufacturing defect).

Types of Binoculars 

In addition to the above criteria, it would also be useful to know about types of binoculars, broadly, that are available as well as some specialised versions of them:

Basic Types 

There are two basic types of binoculars, depending on how the prism is placed within each barrel. Prisms are an essential element in binoculars to correct the orientation of the images that reach our eyes (which would otherwise appear upside down). 

Porro Prism: In Porro prism binoculars the prisms are offset from the lens elements.  

The 8×32 Nikon Superior E – note how far apart the barrels are, as typical of Porro prisms 

Roof Prism: In these binoculars, a predominant type among modern versions, the the prisms are placed in line with the other lens elements, enabling a streamlined form. 

The streamlined form of roof prism binoculars (in this case a 10×42 Zeiss Victory T-FL)

All else being equal, Porro prism binocular assembly allows for a wider field of view (however, with greater limitations placed on eye-relief) and greater depth-of-field, but also results in greater bulk than roof prism binoculars. Porro prisms are also easier to assemble and consequently, are usually cheaper than roof prism binoculars of similar specifications. 

Specialist binoculars

Range Finder: Range finders have the ability to measure the distance between the subject and the binoculars – useful for research scientists and the like with such specialised requirements

Image Stabilised: These, typically bulky, binoculars, come with an inbuilt image stabilisation, negating the limitations of higher magnification for handheld use. Those using binoculars predominantly for Star-gazing and/or pelagic birding/whale-watching from boats on choppy waters will appreciate this feature.

Individual Focus/Hands Free Focus: As against the traditional centre focus options in the majority of the binoculars, some come with the ability to focus for each eye (individual focus, for high precision – useful for astronomy, but not at all for terrestrial viewing, where subjects are often on the move), and, some which focus by tracking where your eyes focus (hands free focus)

Marine: Purpose built binoculars, often with emphasis on build attributes that can survive sustained exposure to corrosive sea-spray. It might help to know that many of these models can also float on water. Marine bins can be very useful for whale and birdwatchers, who spend of lot of time looking at shorebirds or in pursuit of pelagic species.

 

The pairs we own/have owned……..

Ravi

I was fortunate to have access to binoculars for nature-viewing during my childhood, thanks to my father, who both introduced me to the wonderful world of wildlife appreciation on our annual holidays to Mudumalai and Kabini (sanctuaries in south India), and also shared his Nikon bins (that’s as much detail as I remember of the hardware) on those trips – an early insight into the wonderful world of nature through binoculars. Later, during my early field research days (as a student of conservation biology), I bought myself a pair of Nikon Monarchs (one of the no frills models in the series), primarily for its waterproofing (I was counting crocodiles from boats that were prone to capsize those days, and as you can see, lived to tell the tale, albeit of binoculars). All I can recall now was that they served me well (but something about the build quality was not as appealing). There is a hazy recollection of one or two cheap pairs before this, but the sum of what I can remember from those ownership experiences was me having to squint through perpetually misaligned optics. 

Then came the first real ‘pair’ of binoculars that I had the absolute pleasure to look through – an aged and well used (objectives considerably scratched), built-like-a-tank, Swarovski 10×42 SLC. Despite all that evident abuse, what followed was among the most memorable years of nature observation, thanks in large part to these superb glasses – a full (encompassing), bright, sharp view matched with the solid (survived monsoons, butterfingers, slush and hard rock on countless occasions) grippy (great for my large hands) body and smooth focusing wheel. Aside from the optics and build quality I have a special affinity for the brand thanks to their superb customer service. When I was a graduate student in the US I made a sensible decision to mail the pair to Swarovski’s Repair US Centre for service, expecting a considerable charge for their effort. Instead I opened my mail, one (fine, as it turned out) day, to find a brand new rubber housing, eye-cups and (generously padded) neck-strap on them, all this done free of charge ((even though I bought it used, with no record of original ownership!)

As a family of wildlife enthusiasts, it was not viable to sustain our collective enthusiasm to simultaneously look through the Swarovski and having been used to premium optics, it was difficult to go back to economy class. But then again, a spartan student budget (a (un?)healthy proportion of which was inevitably spent on libations and pizza), was a definite limiting factor for owning fine optics. The internet came to the rescue, and after reading (much better) binocular guides than this, I settled on a 8×32 Nikon Superior E – optically as good as, even surpassing, some of the so called  ‘Alpha’ binoculars (usually models from Zeiss, Leica, Swarovski), but at a third of the price! Till date, this was the best pair of binoculars I have had the pleasure of looking through – a crisp, clear, wide view, with bright, vibrant colours and the subjects popping out of the background, 3D like (among the upsides of Porro prism binoculars). The one big minus in the viewing ergonomics was that I had to manipulate the binoculars to a very particular angle on my spectacles to appreciate the entire image circle (this was much easier to achieve without the glasses though and I eventually mastered using the bins even with the glasses on). The binoculars were compact, but also fit nicely in my large hands, had a solid metal casing giving it a well-built feel and the focusing was smooth and responsive, yet tactile.  What it lacked though was close focusing ability and weatherproofing (a big notch on the minus for nature enthusiasts). Build quality issues were evident also, in the flimsy rubber eyecups, and, also when bits would come loose within the barrels (I suspect those were bits of sealant which were not suitable for the heat and humidity of the field conditions where I frequented). While the excellent customer service (not as good as Swarovski) in the US were kind enough to repair or even replace the binocs free of charge (!), this happened so often (I think the 4th time I sent back the binos for the same issue) that they replaced it with a new 8×42 Nikon Monarch HG! (They had stopped manufacturing the Superior E’s, unfortunately, sometime between when I bought it in 2006 and 2018, when Nikon USA sent back the Monarch as a replacement). 

The Nikon Monarch HG is a classic example of a modern, premium roof prism binoculars and does everything very well – almost as well as binoculars which cost twice as much. The image is full (with good edge to edge sharpness), very wide (with an impressive 8.3° angle of view) clear and bright, with good contrast and natural colours. These bins are also light weight, fit great on my large hands, focusses close-up, has ample eye relief and is weatherproof. While I cannot comment on the build quality, with no (thankfully) real life incidents to test this attribute (it does feel a little flimsier than the alphas though), I did find that the body was more easily worn than its pricier big brothers. Optically, perhaps the one drawback is to do with noticeable colour fringing under challenging (backlit) conditions (despite the use of ED glass) – another aspect that the very top-end binoculars often excel at controlling. While I have not done a side-by-side comparison, I found these binoculars more than adequate in low light – an ‘as good as it gets’ attribute of a naturalist’s binoculars. A very worthy all-rounder and easily the best value for money (although, technically I did not buy them!) proposition among all the binoculars that I have used. 

Somewhere between the transformation of the Nikon Superior E to Monarch HG our family of nature enthusiasts was growing ever larger and I wanted to invest in another pair of Alpha Binoculars. I would have gone for the Swarovski EL’s, given my splendid ownership experience with the heavily used SLC. However, one day, at a Bird Fair – which had stalls of innumerable binocular manufactures showing off their wares, with a lake full of waterfowl to test the optics, enough to make an enthusiast’s weak knees go weaker, I happened to have the pleasure of looking through a pair of 8×32 Zeiss Victory FL. The fabulously bright, encompassing view was very special indeed (to put things in perspective this experience was in the middle of looking through some of the world’s (other) top binoculars, so some pretty great basis for comparison). The quest in earnest for this model in the used market (otherwise well outside my budget), proved fruitless for a couple of months until I came across a listing for Zeiss 10×42 Victory T FL, at a price I could just about justify. Not exactly the model that I wanted, but online reviews seemed to suggest that these were just as good, and I emptied my wallet for a pair. As it turned out, there was lots to love about these bins, from the crisp, clear, contrasty, bright, full and sharp view, with great natural colours, in all manner of lighting conditions and how effortless it was to look through them (easy to achieve the full image circle and no eye-strain whatsoever during extended use) and its buttery smooth focusing. They also felt reasonably well built (not as solid as the Swarovski SLC), quite light weight for its size and fit great on my large hands. However, I could not discern that ‘special view’ that I enjoyed through the 8×32 Victory FLs. There were, however, some issues with seemingly cheaper plastic used for some parts – not what one would expect in these top end binoculars. This fact unraveled when I dropped this pair gently, one evening, just a couple of feet to the floor, to ‘dent’ one of the (hitherto) extendable eye cups (jamming the movement). However, it was easy enough to fix for free through their excellent US warranty and customer service. Another time, the drop was rather more dramatic as I slipped on a jungle stream and the binoculars were flung from around my neck to come to rest on some hard rock, a few feet away from my prone body (which I discovered, while frantically looking around, with one side of my spectacles hanging just about the tip of my nose, while the other stayed put over the eye, somewhat aiding the search effort). Sadly, this resulted in breaking off the slot, another seemingly cheap bit of plastic, that that attaches the neck strap to the binoculars, making it impossible to lug around hands free (until I improvised attaching it to a harness, with the aid of high quality rubber band in place of the broken slot). Amazingly though, this drop and a subsequent one of similar magnitude, did not damage the optics in anyway, which remain stoically delightful (I am looking for some solid wood to touch just as I write this). 

Ganesh

(Coming soon)

Some Basics of Binocular Maintenance

Preening your binoculars regularly is essential for a happy, long-lasting relationship with them. Here are some basics:


– As cumbersome as it can be, do rid your binoculars of dust and grime that inevitably accumulates during nature-observation oriented travels. Be sure to get into the nooks and crannies of the body, with a soft cloth (damp is ideal if your bins has some weatherproofing at least, but wipe clean with dry or keep in airy place until fully dry) and cotton buds for those really difficult spaces (and believe me, there are a few). If your binoculars are waterproof, you can even rinse with water and dab dry. Do not use any soaps/alcohol/detergents in the cleaning process. 


– While cleaning lenses, you have to take special care to protect the special coatings that enhance the view through the bins. Only use soft, lint free cloth, or, a ball of cotton wool, to clean the lens surfaces, and make sure you get rid of the dust on them, by blowing and/or lightly dusting with a soft brush (made specifically for use on optics), before you start the cleaning process. Clean with a circular motion with minimal pressure. For stubborn smudges, use only lens cleaning wipes, made specifically for cameras lenses and binoculars (they come pre-moistened with chemicals that are easy on lens coatings). 


– Water/Fog Proof binoculars are typically hassle free to store (with minimal chances of fungus growing on the inside elements), however, regardless of their moisture proofing, it is best to store binoculars in a well ventilated and well lit location. If you live in extremely humid conditions you might consider storing your binoculars in a dehumidifying cabinet (where the humidity levels are controlled within the cabinet).

A glance at some binocular jargon

Eye-piece: The narrow end of the lens that one looks through the binoculars from

Objective Lens: The lenses from where lights enter the binoculars (the broad-end located opposite the eye-pieces)

Exit Pupil: The image circle formed on the eye-piece, the diameter of which is calculated by dividing the size of the objective lens by the magnification

Angle (Field) of View: The maximum potential angle or width that you can view through your binoculars at a given distance.

Eye Relief: The range of distances from the eye-piece to the eyes that allow for a full image circle to be observed.

Focusing Wheel: A component, typically located at the ‘bridge’ of the binoculars, which one adjusts to achieve a sharp image.

Image Circle: The circular image as seen through the binoculars

Chromatic Aberration: Unnatural colour fringing that is especially evident while looking at a subject against the light

Rain guard: Caps that protect the eye-pieces from the elements. It is desirable to buy a one pice guard that attaches to the neck strap (if you use one), which makes it easier to use.

Shoulder Harness: A contraption (replacing the neck strap) that shifts the weight of your binoculars from your neck to your (often stronger) shoulders.

Tripod Adapter: A device which helps you connect your binoculars to a tripod. A useful ability for high powered binoculars that are difficult to hold steady by hand and especially relevant for star-gazers (in the nature-watcher scheme of things)

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