Binoculars, Part 2: seeing is believing

Paul Smith
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A couple of weeks ago, I talked about a decent pair of binoculars being one of man’s and woman’s essential outdoor gear items. I gave a bit of history, but didn’t say much on the technical side of things.

You don’t need to be an optical expert to choose decent field glasses, but it’s nice to know the basics. If not, you’re depending only on advertising literature, sales person advice and hearsay to make a decision that can separate you from a significant sum of your hard-earned money.

Quality glass isn’t typically cheap. But if you make the right choice, you only need purchase binoculars once. They will certainly last a lifetime.

Binoculars are basically two telescopes mechanically linked together, one for each eye, so just about everything I say applies to both telescopes and binoculars. Who cares about telescopes? We’re hunters, shooters, wanderers and anglers, not astronomers.

I know this, but the spotting scopes used by hunters to evaluate game from great distances are no different than those pointed skyward. They’re also fantastic to have at the shooting range to see your bullet holes without walking to the target.

And telescopes of either variety are close cousins to the scopes that sit on our moose and coyote rifles. Knowing something about optical basics is definitely a practical thing.

The first choice facing you is whether to go with a roof prism or porro prism design.

The porro design was invented in the mid 1800s by an Italian, Ignazio Porro, hence the name. The advantage is that all the optical surfaces are reflective, which makes for a simple and easy-to-construct system. So typically, porro style binoculars sell at a cheaper price, given the same optical quality.

You can easily recognize them by their physical shape. The objective lenses are further apart then the ocular ones. (The ocular lenses are those closest to the eyes, for those not familiar with the terminology.)

These are the sort of binoculars that you see sitting on window ledges in many homes with a view, typical outport houses built close to the sea.

If you aren’t toting your glasses afield much, and you want the best bang for the buck, porro prism binoculars may indeed be the best choice. They are cheaper, but heavier and much more bulky.

Roof prism binoculars have straight line tubes with the objective and ocular lenses centred on the same axis. This makes for a much lighter and more compact design, but the prisms necessary to achieve this are much more complex and expensive to manufacture.

I’d suggest never scrimping on roof prism glasses. If you can’t afford a good pair, wait until you have the money, or buy the traditional porro prisms.

Cheap roof prism binoculars are generally horrible to use and strain one’s eyes in very short order. But the top quality ones are fantastic and well worth the investment.

My favourite field glasses are a pair of Vortex roof prism design 8 x 42s. In optical lingo, that means they magnify by eight times and the objective lens is 42mm in diameter.

They are big enough to perform well in low light and are effortless to carry all day on a neck lanyard.

I hardly ever go in the woods without them.

Should you buy the most magnification possible? No, most definitely not. This is probably the biggest misunderstanding in optics. Everything comes at a cost. Tradeoffs abound in engineering.

Higher magnification means you need more light to get the same image brightness. With all else equal, 8 x 50s are much brighter than 8 x 40s. In my opinion 8 x 40s are a perfect balance of portability and low light capability. If I wanted more magnification, I would go to 10 x 50s, and train my neck muscles before moose season.  I would never consider 10 x 40s.

And binoculars over 10-power, in my opinion, are overkill. They are just too difficult to hold steady enough for a sensible stable image. Anything above 12-power is useless without a rock solid rest or tripod, and even 12s are a tad dicey, at least in my non-surgeon hands.



What’s all this mumbo jumbo about lens coatings?

These are antireflective optical treatments that assist in light transmission and generally make the optics brighter. This is a very good thing if you want to spot that trophy bull feeding along a dark tree line at dusk. You would be amazed at how bright some of the high-end binoculars really are. They literally allow you to see in the dark. But, of course, these magical chemical glass coatings have a price tag.  

Here’s what to look for:

‰    Coated means a single layer of antireflection coating on some lens elements, usually the first and last elements, or at least the only ones you can see. This is often just window dressing so the company can charge a bit more at the shop.

‰    Fully coated means that all the air-to-glass surfaces are coated. This is good. This is what you want when you spend hard earned money for quality glass. So, now we have all glass surfaces with a single layer of chemical treatment. More coats would be even better, right? Yes indeed. And most often the best optics are multicoated.

‰    Fully multi-coated means that all the air to glass surfaces have received multiple layers of antireflection coatings, and this is what you really want in your field binoculars. Now you can see those moose and birds in the nastiest of conditions.

There’s still tons more I can say about binoculars, and I surely will write more in the future. Optics is a favourite subject for me, especially during Friday night rum chats at the cabin. The bottom line is to buy the best quality that your budget allows.

There are some fantastic binoculars out there for a reasonable price from companies like Leupold, Vortex, Burris, Pentax, Nikon and so on. You can easily pick up a decent pair of hunting binoculars for around the $200 mark.

The cheaper stuff at department stores is generally very poor quality, both in terms of mechanical construction and optical quality.

If you don’t believe me, take a peek through a good pair of European binoculars like Zeiss or Swarovski late in the evening.

Then look through a pair of $50 bargain glasses. The difference is night and day. Without a doubt, you will put a pair on your wish list.

If you are interested in browsing some good glass, have a look at or They offer great binoculars at pretty fair prices.


 Paul Smith, a native of Spaniard’s Bay, fishes and wanders the outdoors at every opportunity.  He can be contacted at

Organizations: Leupold

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