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Aug 032014
 
Bigger is not always better with binoculars.

Bigger is not always better with binoculars.

One of the most useful pieces of ‘force multiplying’ equipment in your prepper kit is a good pair of binoculars.

Unfortunately, many people have little idea of what makes a pair of binoculars good or not so good, and with mass marketed binoculars usually being low quality, few people appreciate how helpful a good pair of binoculars can be when it comes to boosting your range of vision.  Furthermore, very few of the many different models of binoculars come anywhere close to meeting the requirements of a ‘good’ pair of binoculars, and so by statistical chance alone, most people end up having bought a poorly performing pair of binoculars.

There are many things to consider when choosing a pair of binoculars.  But these various issues are all easy to understand, and unlike evaluating high-end audio gear, for example – it is easy to tell if the binoculars you are considering are ‘good’ or ‘bad’.

Different Design Types

There are two major categories of binoculars to choose from.  One type is what we’d term ‘straight through’ binoculars (their official name is ‘roof prism’ binoculars) and they are distinguished by having more or less straight tubes from the objective lens (the big lens that faces towards what you are looking at) to the eyepiece on each side.

These binoculars also look similar to a third type of binocular, known as ‘Galilean binoculars’, but you’re unlikely to see them when looking for prepper type field binoculars and so we will pretend they don’t exist.  They are most commonly seen as opera/theater glasses these days.

The other major type is what could be termed ‘offset’ binoculars and which are more properly named Porro prism binoculars.  These have the eyepieces closer together than the objective lenses.

There are several reasons why we recommend you consider only offset type binoculars.  They can have larger objective lenses (read on to learn why this is important), they allow more light to pass through than roof prism binoculars (making for brighter images, particularly important in low light and night conditions) and the greater distance between the two objective lenses helps improve the stereoscopic perception and awareness of distance.  They also tend to be smaller in length, because the optical path travels in a sort of letter ‘Z’ through them rather than directly through them.

Note that there are also some very stupidly designed ‘reverse Porro’ binoculars, where instead of having the objective lenses spaced further apart than the eyepieces, they ‘zig in rather than out’ and are closer together than your eyepieces.  You will get less 3D depth perception with these, and we totally do not recommend them.

How Powerful Should Your Binoculars Be?

By ‘powerful’ we mean how many times magnification your binoculars may offer.  The answer to this question tricks a lot of people, including my parents, many years ago.

I remember as a young boy I desperately wanted a pair of binoculars, and so my parents gave me a pair one birthday.  Bless them, they wanted to get me the ‘best’ set they could, so they got a pair with 12x magnification.

But they did not understand that more magnification was not synonymous with better.  A 12x magnification was too much for hand-held binoculars.  The greatly magnified images jumped about too much and it was unpleasant to use the binoculars without some sort of steadying support.

So, to my parents’ surprise – and possibly to your surprise also, there is such a thing as ‘too much’ magnification.

On the other hand, there’s little benefit to get a pair of binoculars that only offers two or three times magnification, when there are perfectly good binoculars offering more than twice as much magnification.

To make a potentially long story short, the best compromise for portable handheld binoculars, between too much magnification making for too unstable an image, and too little magnification making for less overall value, seems to be at the seven or possibly eight times magnification.

 – Special Case – Fixed Observation Posts

Our earlier discussion about magnification assumed we were talking about a portable pair of binoculars that you would want to be able to use without the need for support.

If you are instead considering a pair of binoculars that could be mounted on a stand or tripod or other stable platform, and if weight issues are also not so relevant, then there is no reason not to consider more powerful binoculars.  In such a case, by all means get any power you feel appropriate, while noting that if the ratio between magnification and objective lens diameter gets too small, their value as night glasses will diminish appreciably (explained below).

Don’t go wild and crazy, particularly in a fixed OP.  In such a case, you know what vision ranges you need.  Maybe there’s a tree line a couple of hundred yards away, or a rise/fall in land that limits your vision.  You’re unlikely to want or need to be able to clearly see the buttons on a guy’s jacket a mile away, and if you do have that need, then you should use a special purpose telescope rather than binoculars.

Zoom Binoculars

Talking about magnification, you can also get zoom binoculars which might give you a magnification range from perhaps three or more times up to some massively greater number – indeed, we’ve seen zoom binoculars offering beyond-crazy maximum zoom capabilities, sometimes in excess of 100x.

The chances are your camera has a zoom lens, so you know how great they are.  So doesn’t it make sense to have a zoom function on your binoculars, too?

The answer to this is a very emphatic ‘No!’.

There are several reasons why zoom technology – so brilliantly wonderful on a camera – does not translate well to binoculars.

First, remember that any magnification greater than about 8x starts to become problematic from the perspective of keeping the image stable while hand-holding binoculars unsupported.

Second, greater zoom ranges start to get an inappropriate ratio between magnification and objective lens diameter (see below).

Third, a zoom lens has a lot of optical compromises in it.  These can be electronically processed out in a camera, but will be visible and problematic in a pair of binoculars.  The extra lens elements in the zoom will also add to the weight of the binoculars.

Fourth, remember that a pair of binoculars has two independent ‘telescopes’ that are joined together.  If you have a zoom capability, the zooming has to work identically in each ‘telescope tube’; if it doesn’t, then your eyes will be stressed and will lose the ability to merge the two images into one single image in your brain.  We’re unaware of any zoom binoculars on the market today with sufficient build quality as to avoid this problem.

Fifth, a zoom lens has a much narrower field of view, particularly at lower magnifications, than a regular lens.  This makes it harder to quickly point your binoculars at something you saw in the distance and be sure you’re pointing in the right direction, and also reduces the amount of situational awareness you’ll get because the area you are monitoring has shrunk.

We could probably come up with some more disadvantages too, but surely this is enough for you.  Don’t get a pair of zoom binoculars.

Well, actually, here’s one final consideration.  Because zoom binoculars are a gimmick that ‘serious’ users would never select, it seems that the leading manufacturers of binoculars don’t bother making them, so you’re restricted to lower quality suppliers of a product that is incapable of ever being high quality to start with.

Objective Lens Size

If you hold a pair of binoculars away from you and look through the eyepieces, you’ll notice that the image appears as a small circle within the broader eyepiece lens.

Here’s a key consideration.  You want the size of that small circle to be at least as big as the size of your eye pupil (the black circle in the middle of your eye).  Now, as you know, your pupil changes in size – in bright light, it gets smaller, and in dim light, it gets larger.

You want the size of the image to be bigger than the biggest size your pupil ever gets.  If it is smaller, then you are defeating the whole purpose of your pupil growing in size to admit more light in low light conditions.  On the other hand, if it is bigger than your pupil, there is no harm done at all.

Another benefit of a larger viewing image is that it makes it less critical to exactly center the eyepieces on your eyes, because even if your eyes and pupils are a bit off-center (compared to the binoculars – the ‘interpupillary distance’), they are still being fully exposed to the image within the eyepieces.

An adult’s pupil grows to about 7mm in diameter in low light (and as we age, it shrinks), so you want these circles to be at least 7mm in diameter.  Now – how do you know what size the circles are (other than measuring them)?

Happily, this is very easy to calculate.  Divide the diameter of the objective lens (the big one that faces towards what you’re looking at) by the magnification power, and that tells you the diameter of the image your eyes see.  For example, a set of 8×24 binoculars would have a tiny 3mm diameter image in each eyepiece.

Remember we said you should get binoculars with seven or eight times magnification?  Well, multiply those numbers by 7 to get the necessary objective diameters such binoculars should have – at least 49mm in the case of seven times magnification, and at least 56mm in the case of eight times magnification.

This is why the 7×50 binoculars have become pretty much the ‘gold standard’ and optimum compromise point for serious professional grade binoculars.  A pair of 8×56 binoculars would be slightly better in terms of magnification, but they’d also be appreciably heavier (the lens would have to be 30% bigger and overall, the binoculars would start to become too big, bulky and heavy for convenient use).

Field of View

Binoculars have a varying field of view, depending on their design and magnification.  The field of view relates to how wide an image you can see, and is generally specified either in terms of degrees, or in terms of how wide an image you get at a specific distance, for example, perhaps you might be looking at a pair of binoculars that offers a 5º field of view, or a 262.5 ft field of view when looking at things 1000 ft away.

To convert from degrees to feet (at 1000 ft) simply multiple the degrees by 52.5 (or divide the feet by the same 52.5 factor).  If you’re being quoted so many feet at 1000 yards, divide by 157.5 to get degrees (or divide by three to get feet at 1000 ft).

The wider the field of view, the easier it is to get sighted in on something, the easier it is to track fast-moving objects, and of course, the more you can see simultaneously.  The bigger the better for this parameter.

But remember that, in general, the greater the magnification, the lower the field of view.  Normally it is not appropriate to sacrifice magnification for field of view.  Decide the magnification you want first, then get the best field of view available for that magnification second.

Image Stabilization

If you have a heavy-duty budget for binoculars, you might be interested in considering a pair that offers image stabilization.  These are exactly as the name implies – they have built-in stabilizers that steady the image by adjusting the optics, and so allow you to enjoy handheld stable images with much greater magnification.

So that’s a plus.  But there are minuses.  As preppers, we want to have high quality but ultra-reliable gear, and adding all the micro electronics and electrical stuff that goes into image stabilization greatly increases the likelihood of sooner or later, something going wrong.  If the stabilization fails in a bad way – ie, one lens out of alignment with the other – then the binoculars become useless.

The image stabilization also requires battery power.  That’s probably not a deal breaker by itself, but it’s another pinprick of aggravation and hassle.  You’re probably also looking at another pound or more of weight because of the extra stuff inside.

The biggest argument against them though is that unless the objective lens diameter has grown in size to match the increased magnification, you are getting something that works only in bright light and which becomes increasingly useless in dimmer light.

We suggest you don’t buy an image stabilized pair of binoculars.  Spend the money on a truly high quality pair of standard binoculars – indeed, maybe you can even buy two pairs of standard binoculars for the same cost.

Waterproofing

Maybe you’re not planning on dunking your binoculars in the ocean.  But how about using them in the rain?  A waterproof pair of binoculars will of course be more resistant to rain effects and humidity, as well as to accidental immersion in puddles or anything else.

Most higher quality binoculars are waterproof, indeed, let’s simply say that if the binoculars are not waterproof, then who knows what other design compromises exist, so don’t buy them.

As you probably know, there are varying degrees of waterproof capabilities, often expressed in terms of how many minutes at what depth of water can be withstood.  So don’t just assume that all waterproof claims are of equal validity – some will probably be better than others.

As well as claims about being waterproof, some binoculars claim to be fogproof.  This means they have probably had their interiors pressurized with moisture free nitrogen.  All fogproof binoculars are necessarily waterproof too, but not all waterproof binoculars are also fogproof.

Focusing Options

There are three types of focus offered on binoculars.  The simplest is a fixed focus that you can’t adjust, whether you want to or not.  The next most simple is a single or central focus knob that adjusts the focus in both sides of the binoculars simultaneously.

The least simple is having separate focusing controls for each side of the binoculars.

We’d suggest you do not settle for fixed focus.  While you probably don’t need to adjust the focus at all when switching between looking at something 75 yards and 150 yards and 300 yards apart, even with variable focus capabilities, if you occasionally use your binoculars to look at closer things, then you will definitely benefit from being able to adjust focus.

A fixed focus lens is a compromise that is slightly out of focus everywhere, and increasingly out of focus to the point of uselessness at short ranges.  Why would you ever want a slightly out of focus picture?  Isn’t the importance of the best possible image worth the slight hassle of turning a knob slightly?  Where is the logic of potentially paying $100-$500 more for a high quality pair of binoculars, only to degrade the image by settling for a fixed focus?

For hopefully obvious reasons, we definitely do not recommend having separate focus knobs for each side of the binoculars.  That is just way to inconvenient and complicated.  We might even prefer to have a fixed focus set of binoculars before accepting the double hassle of focusing twice each time we changed the distance between us and whatever we were looking for!

Some focusing systems involve turning a wheel/knob, around and around, to adjust focus, and it can take a fair while to do this.  Others have a ‘fast focus’ feature – some sort of lever that you only need to move a slight distance to go from closest to most distant focus settings.  That might seem like a benefit, but you lose the fine element of focus control with the turning knob, so we suggest you stick to a normal focus mechanism.

Next, let’s consider a related feature.

Diopter Adjustments

Most of us have one eye that is ‘better’ than the other, particularly as we age and our eyes start to deteriorate.  If you have corrective lenses, you are already familiar with how their degree of corrective strength is measured in diopters.

All good binoculars have a diopter adjustment on one of the two sides.  You use this to balance out your two eyes.  The way to do it is simple.  First, focus the side that does not have the diopter adjustment on something, with your other eye shut.  When you have that exactly in focus, close your eye on that side and open the eye on the other side, and turn the diopter adjustment to then get that side exactly in focus, too.

Once you’ve made this adjustment you won’t need to do it again, but of course if someone else uses your binoculars, they will want to adjust them for their own vision.  So it is helpful to make a note of your diopter setting, so when you get them back, you know where to set it without needing to go through the whole calibration process again.

It would also be a kindness, when passing the binoculars to someone else, to zero out the diopter adjustment for them.

Glass Coatings

Due to various interesting and complicated optical things, when light enters (or exits) a glass lens it gets slightly altered, and some light bounces back.  The bounced back light reduces the brightness of the final image you see through the binoculars, and the slight alterations create distortion in the image you look at.

So, to minimize these things, good  quality optics have coatings of special material on them.  You definitely want coated optics in your binoculars.

Now for the trick.  Some binoculars will describe themselves as having ‘coated optics’, some will say ‘fully coated’, some will say ‘multi-coated’ and still others will say ‘fully multi-coated’.

You can probably guess that the best is ‘fully multi-coated’.  Let’s explain what the others probably mean.

  • A claim for ‘coated optics’ probably means that some lens surfaces are coated with a single layer coating, but others have no coating at all.
  • A claim for ‘fully coated optics’ means that all lens surfaces have a coating, but it is probably only a single layer coating.
  • A claim for ‘multi-coated optics’ means that some lens surfaces have multi-layered coatings, but others probably have nothing.
  • And, of course, the ‘fully multi-coated’ means all lens surfaces have multiple coatings on them.  That is generally the best scenario to hope for.

One last thing about coatings.  Not all coatings are the same, and we have a suspicion that some low-priced low quality binoculars that boast of an optical coating have a fairly useless coating that does almost nothing at all to improve the image quality.  You can place your trust in the big brand names, but need to look at generic brands with extra careful scrutiny.

Optical Quality

It is hard to accurately assess the optical quality of a pair of binoculars just by looking at them, but there are some things you can readily see.  Here are several things to look for.

The first is to check there is no darkening of the picture around the edges.  You want even brightness all the way through.

The next is to check that everything is simultaneously in focus, both in the middle and at the edges.

Make sure straight lines are straight and aren’t curving (either in or out).  Move the lines (both horizontal and vertical) around – curving is most likely to appear around the edges of the image rather than in the center.

Next, look at a scene that has fairly bright light.  You don’t want any ‘flares’ or ‘streaking’ of the image.  Look around the edges of objects with light backgrounds, and make sure the object edges aren’t ringed with color fringes.

Now, hold the binoculars several feet away from you and look at the two small circles of image that you can see as if they were on the eyepiece lenses.  Rotate the binoculars so these small circles travel out to the edges of the eyepieces, and then have them travel around the edges in a big circle.  What you are looking for is to make sure that there aren’t squares inside the circles, greying out the gap between the outside of the square and the outside of the circle.  A little bit of this is probably okay, but you’ll see large differences in this effect between different binoculars.

Do these checks both when focusing on something up close and something far away.

Also, make sure that when you look through them, the images from both sides merge into one single image.  If they don’t do this, it is likely that one of the sides of the binoculars is out of alignment with the other side, and that will always (until/unless fixed) interfere with being able to comfortably and effortlessly use them as an extension of your own eyesight.

These simple tests will give you a degree of comfort as to the quality of the optics.

Construction and Ease of Repair

This is a bit more subjective, but do the binoculars appear to be solidly constructed and well made?  We prefer rubberized (sometimes called ‘armored’) type finishes, in the hope that if (when!) we drop them, the rubber surface will absorb some of the shock of having them dropped.  The rubber also quietens them – if something knocks against them, less sound will result, and that is sometimes helpful too.

One important test is to screw the focus adjustment all the way so the eyepieces move furthest out from the body of the binoculars.  Then lightly press on each of the two eyepieces and see if it wobbles.  It is important they stay solidly at the distance they are at, or else the varying pressure you’ll place on them during normal use will cause them to get out of focus with each other.  Poorer quality binoculars often display some weakness with this, good quality ones do not.

A similar consideration indicative of quality (or not) is you don’t want any slack or slop in the focusing mechanism, or in the way you can open up or close down the binoculars to adjust the distance between the eyepieces.

Are the two tubes held absolutely solidly in alignment with each other.  Even the slightest misalignment will interfere with your brain’s ability to blend the two images together.  Make sure that there is no susceptibility to any movement of either tube with respect to the other.

In terms of repair, can you readily access the interior of the binoculars and adjust the prisms?  If you drop them (we always have the carry strap around our neck so as to minimize the danger of dropping, and you should too) there’s a danger the prisms will be knocked out of alignment and you’ll want to be able to go in and try to realign them.  The prisms should not be glued in place, and you should be able to unscrew the parts of the binoculars to get inside.

Note that if you open up ‘fog proof’ binoculars, when you reseal them they will probably no longer be fog proof.  If this was an essential thing for you, you could at least flush them with wine bottle gas before sealing them up again, and that would displace much of the moisture bearing regular air.

Weight

This is a deceptive concept.  On the one hand, if you will be carrying binoculars with you, you want them as light as possible.  On the other hand, well-built and ‘solid’ binoculars will probably also be heavier.

That’s not to say that heavier binoculars are automatically better made and stronger than lighter ones.  We suggest you consider all other factors first, and only then, think about weight and possibly, if you are sure it is not compromising the quality of the binoculars, give preference to lighter weight.

Extra Features

Some binoculars super-impose a compass display so you know what compass bearing you are looking at.  That’s a moderately useful feature in theory, but the compasses are often much less than perfectly accurate, which greatly detracts from your ability to pass sighting data on to other people.  In addition, if you do not have the binoculars flat and level, the compass may not spin so freely.  Yes, you’ve got a $500 pair of binoculars with a 50c ‘toy’ compass inside – lucky you!

Some binoculars have ‘range finding’ marks on them a bit like rifle sights.  If you know the size of something you are looking at, the range finding marks help you to estimate its distance from you.  That may be a useful feature, particularly when away from home, because around your retreat, you’ll have of course already plotted out distances between all landmarks and relevant features (won’t you!).

Note that both compasses and range finding marks might be hard to see in the dark, and/or might require batteries for illumination.  We don’t consider either as a ‘must have’ feature.

Some binoculars have laser range-finders built into them.  That’s a lovely feature to have, but don’t get carried away and compromise on other features just to get the laser range-finder, because it is easy enough to buy a separate standalone laser rangefinder.

Indeed, we’d generally recommend you to get a separate unit, because it is probably much cheaper to do so – they cost about $100-$150 and are accurate to within a yard at ranges of potentially up to 600 yards, depending on what you’re trying to bounce the laser beam off (the bigger and more reflective the surface you are shining the laser at, the better).  Long range precision shooters love these devices.

Make sure the binoculars have lens caps for all four lenses, and also some type of carry case.  You want a neck strap for the binoculars and a second neck strap for the carry case.

Summary

We suggest you buy a good pair of 7 x 50 binoculars generally in line with the comments above.  Expect to pay over $100 but be reluctant to pay over $500 (based on August 2014 pricing on Amazon).  Although there definitely are some lovely binoculars available for much more money, you’ll get very good binoculars within this price range that you’ll be very happy with.

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David Spero[suffusion-the-author display='description']

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