How to Buy Binoculars

J.P Lemirere invented the very first binoculars in 1825, and ever since, they’ve been utilized in a multitude of different activities. Binoculars are used for sightseeing, birdwatching, fishing, hiking, watching plays in theaters, in addition to a ton of other things.

Nevertheless, this doesn’t make it any easier to figure out how to buy binoculars. The market is flooded with different models, which all come with various features and numbers on them.

Today, we’ll simplify all these numbers for you, have you understand what each of them means, and how they’ll affect your experience. That way, when you purchase your pair of binoculars, you’ll be confident in your decision and completely satisfied with your investment.


The very first thing we’ll talk about is the prism. If we want to sum up the prism in simple words, we’ll say that it’s the binoculars’ mechanism.

All of the physics that goes into making a pair of binoculars is put into the prism as it works on tailoring and flipping the image horizontally and vertically for you to see the image as if it’s in real life. There are two different types of prisms; the Roof and the Porro. We’ll discuss both momentarily.


The roof prism is the newer variety available today; that’s one of the many reasons why they’re pricier than the Porro ones. Roof prisms are placed so that the light passes in a straight line, which allows for a lot more light to come through the lenses, and therefore the image is sharper, clearer, and can support higher magnifications.

They’re also lighter and more compact in size due to the faux-simplicity in their design. As a result, the image achieved by these prisms is the fruit of complexity, which is another reason for their hefty price tag.


Porro prisms are the first set of prisms used for binoculars, and they’re still used widely to this day due to a set of advantages, including affordability. The two prisms placed inside act as an amplifier and an inverter to deliver the correct image to your eyes.

The properties of the image received through Porro prisms include a wide field of view and better perception. Unfortunately, though, Porro prisms are bulkier and heavier than Roof ones.

Glass Type

As the industry of binoculars has evolved over the years, the types of glass used to manufacture them have increased as well. Today, we have three main varieties that monopolize the market: BAK4, BK7, and SK15.


BAK4 or Barium Crown optical glass is the top choice for prisms, as it transmits a more generous amount of light due to its high refractive index and round exit pupil. Moreover, it allows for a clearer, sharper image. Yet, this image has a price, and that’s the expensive price tag carried by the BAK4 binoculars.


BAK7 is another variety of Barium Crown glass. It, too, offers excellent light transmission; however, it has a square exit pupil, which reduces the amount of light entering. But, it remains more affordable than Its sibling, the BAK4.


SK15 comes with a distinct collection of features, as it has a very high refractive index and low dispersion. Consequently, it’s an unusual choice for specific people.


You must decide on a kind of binocular lens beforehand, as your lens will outline your view. Glass lenses are the most common these days; still, they do reflect some light, which can make the image a little bit blurry.

Nonetheless, if you choose to go for extra-low dispersion glass lenses, you’d find your image to be a lot clearer and with a higher degree of contrast.

Furthermore, according to your usage, you might want to go for plastic lenses if you’re prone to dropping your binoculars frequently. Nevertheless, let’s talk more in-depth about the objective lens and what its job is.

Objective Lens

The number related to the objective lens is the second number in the main number placed on any binoculars set. For example, you’ll find that your binoculars have an equation of 7×42. The 7 means the magnification power, while the 42 indicates the objective lens’s diameter in millimeters.

Logically, the wider the objective lens is, the more light you’ll receive, and, therefore, the image will be sharper and more evident. Still, don’t forget that as your objective lens gets bigger, your binoculars will be heavier, and, of course, vice versa.

Lens Coating

Different coatings are applied for protection against water, heat, and light reflections. In general, if your binoculars’ objectives are coated, they’ll either be “coated,” multicoated,” or “fully-coated.”

Coated means that only one side of the lens has one coating layer on it. Multicoated means that one or more surfaces have one or more coating layers; it depends on every manufacturer. Finally, fully-coated means that all surfaces of the lens have been coated with more than one layer.

Magnification Power

If you have a magnification of seven, this means that the object in front of you looks seven times closer than it really is. You could alternatively go for binoculars that come with zoom magnification to control it yourself.


The focus of binoculars means exactly where you want the image to sharpen. You need to be seeing clearly, even if the object is closer to you. You have two ways of adjusting the focus on your binoculars; the central control in the binoculars bridge adjusts both eyes simultaneously.

Or, you can use the Diopter placed after each eyecup to control each eye individually. The Diopter is also useful for those who wear glasses.

Exit Pupil

Exit pupil means the diameter of focused light that enters the eye. Firstly, you need to know that the human pupil ranges from 1.5 mm to 8.8 mm in diameter according to the room’s degree of light. Hence, the exit pupil needs to be something in between these two numbers.

To see the exit pupil, hold the binoculars 10 inches away from your face; you’ll notice a white spot in the middle; that is the exit people.

Construction Material

One of the essential points that determine how heavy or light your binoculars will be, and therefore will direct you towards certain activities, is the build of the binoculars.


Polycarbonate has a vast range of uses, all due to its efficiency, strength, durability, and, of course, the fact that it’s naturally corrosion-proof. Another great advantage of polycarbonate is its resistance to temperature and the changes issued by temperature.

This means that, unlike metal, which tends to change in size according to the temperature and dislocates the lenses, blurry images overtime, polycarbonate remains the same size. 


Magnesium or magnesium alloy is used due to its durability, strength, and corrosion resistance. The winning card here is its weight, which comes to a couple of ounces below aluminum.


In the end, aluminum remains the most used metal for binoculars. It’s strong, rugged, efficient, affordable, and naturally corrosion-resistant.


Waterproof means that the binoculars can survive a few splashes of water here and there due to the tight O2 seal applied to them. Still, they don’t survive submerging underwater. On the other hand, water-resistant binoculars also come with another type of O2, which is slightly weaker. 

This means that they won’t fog when taken out; however, they’re not designed for water exposure. So, according to your planned activities, you must choose whether you want your binoculars to be waterproof, know the rating of their waterproofness, or just go for water-resistant ones.

Fog Proof

Fogging happens inside the optical tubes due to the air inside them colliding with moisture. 

That’s why, to make the binoculars fog-proof, they replace the air inside the tubes with an inert gas such as nitrogen or argon, which will not allow moisture inside. This means that moving the binoculars from warm areas to cool areas and vice versa will not be a problem anymore.


Let’s face it, binoculars get hit and bumped all the time. That’s why you need to choose ones that are designed for wear and tear. One great way to protect the binoculars is by applying a layer of rubber coating on them, which will protect them.

Final Thoughts

Now that you know how to buy binoculars, you need to decide on what kind of activity you’re going to use those binoculars for. Each activity will require different features and options; bird sighting isn’t the same as hiking, which is radically different from kayaking. 

Consequently, always keep that in mind that a bigger magnification or a pricier pair of binoculars isn’t always the better choice before you hit the markets.

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