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What Does It Mean When a Pair of Binoculars Are Nitrogen-Filled?

Last Updated: 30.11.21


If you’ve been thinking about a new pair of binoculars, you’ll find more info here. Nitrogen-filled binoculars have become very popular nowadays, but few people know that what the nitrogen actually does is protect the item from being internally damaged by water and fungus, making the binoculars better. 



A little bit about binoculars

Ever since they were invented, binoculars have always been man’s answer for trying to see things which are too far away to observe with the naked eye. Since walking on the Moon is a little bit out of hand for most of us and looking a lion right in the eye may not be worth it, these instruments have become quite important to our civilization.

Together with telescopes and magnifying glasses, binoculars are the cool kids of the science of optics and use lenses to pull some pretty neat tricks on the light and offer the viewer a zoomed-in image of what he or she is trying to look at.

When Hans Lippershey managed to invent the first big telescope back in 1609, most people realized that it was only a matter of time before we would be able to shrink that technology enough to be able to fit it into a device which would only cover both our eyes.

It would take two and a half centuries more before a man called Ignacio Porro patents the Porro prism which is still so popular today and is widely used in binoculars manufacturing. However, the early 1900s brought some competition in the form of roof prisms, the other alternative which is also quite popular nowadays.

In plain English, aficionados today still have to make a choice between the added depth and image brightness a Porro prism offers and the higher magnification power available through the use of roof prisms.


Lenses and their applications

Since you’re probably not here for a physics lesson, we’ll just leave it at this: for the magnification process to happen and a far-away image be brought close enough for you to see, we need light. 

Therefore, for centuries, scientists have been working on ways to perfect our ability to control and capture the light, and one of the most important fruits of their work was the might-powerful lens. Through using one, we can control the direction and the quality of light, depending on the shape of it.

As you know, binoculars use lenses to gather light rays around the far-away object so whoever is using them can watch what is happening from a great distance. When it comes to science, the process of light bending at the moment of going from air to a different environment like glass or water is called ‘refraction’. 

After the lens first gathers the light, an instantaneous trip happens to the point of your focus when an eyepiece lens captures it and offers the awaited magnified image. Physicists call this ‘the focal path’ and it can be longer or shorter depending on the size of the device, which therefore explains the size of telescopes. 



Nitrogen’s role in this

So far, we only managed to explain the scientific part of what makes a pair of binoculars so useful. However, when one wants to purchase such a valuable item, there are several things that need to be taken into account such as water and humidity resistance, especially if the binoculars will also be used for fishing.

Since companies and manufacturers like to boast about their product’s specification to increase interest and draw more public, they have started to highlight the fact that their binoculars are filled with nitrogen. It sounds cool and professional and which one among us wouldn’t want to buy a pair, right?

Nevertheless, laymen will not understand exactly why binoculars are filled with nitrogen nor how much good this actually is doing. Therefore, a marketing move leads to confusion and miss-conception about what is actually important when buying this product.

To begin with, we have to point out the obvious fact that optics are meant to be protected from even the slightest impurities and moisture, so manufacturers had to come up with a safe way to do this.

When assembling a pair of binoculars, the greatest care is taken to ensure there is no moisture anywhere. However, since the very air around us contains traces of humidity, it is very possible that this gets trapped and jeopardizes the entire process. To remove this possibility, dry nitrogen gas is run through them.

This gas is pumped using a lot of pressure, to ensure that nothing else also gets inside and to force any impurities present to move out, leaving the binoculars completely dry and clean from the inside. 

After that, the eye-cups need to be sealed right after the nitrogen is injected, for the same safety reasons. For this, manufacturers will use rings made of rubber as it’s a protective material which does not allow the entrance of anything inside it.


Benefits of nitrogen

If you have ever seen a glass bottle that just came out of the freezer, you will understand where we are going with this. Any glass kept in the freezer will have an accumulation of moisture inside it since the low temperature turns the water into fog and it forces it to accumulate on the sides of the bottle.

What would be the result if the same thing happens to your binoculars? You will certainly not be able to see anything through them until they’ve dried up and then it may be too late for what you needed to use them for.

Furthermore, this problem gets even worse when there is plenty of moisture in the air, so say bye-bye to using your binoculars in any humid areas. Therefore, if you’re hunting or watching birds you will have to put a stop to whatever you’re doing and dry the binos, right?

Actually, this is where the mighty nitrogen comes in as a savior of these circumstances, so we thought we should list some of the benefits of nitrogen purging for binoculars.

First and foremost, nitrogen never allows moisture to enter inside the binoculars, which means you will have no problem if you want to look at something while it is raining or take them with you when going swimming.

Second, nitro is not limited to water only but to any and all impurities such as dust, fungus, debris, and even rusting, keeping your favorite pair of binoculars super clean from the inside-out. 

Furthermore, if you do happen to store or forget them in a damp place without any protective measures, you will be quite glad you spent a little extra money and got the nitrogen pair because you will still have a working item. However, while the nitro will make sure no fungus grows inside, this may still happen on the outside so it’s probably better to avoid it. 



What about non-nitrogen filled binoculars?

The main difference between the two types of binoculars known by the wider majority of people is that binoculars designed without nitrogen will get blurred underwater and during foggy weather, while the other ones won’t. 

Another question some people may ask is about the possibility of nitrogen leaking out of the apparatus. However, rest assured that since nitrogen is filled under extreme pressure, the chances are slim-to-none. Even if that happens, the binocular will still be water-proof. 

Having said all that, it does not necessarily mean that only nitrogen-filled binoculars are worth your money. If you are thinking about buying a pair, don’t overlook the importance of magnification, field of view, prisms, and glass type in addition to the nitrogen part.

Even though having all of those is a win-win situation, it’s quite important to know what exactly you are going to use your new pair of binoculars for. Test all aspects, carefully consider your budget and only after that make an educated decision based on how much you are willing to spend for them. 

Nitrogen-filled binoculars are imperative for cold and humid places, where fog is very common and might severely impede a lesser pair from being useful. The same thing goes for people who live near coastal areas since the air there is always loaded with moisture and this will promote the growth of fungus inside the binoculars.

Swimmers, underwater divers, and kayakers will also find it quite important to get a nitrogen pair since they will not be able to fully enjoy their ventures with wet or foggy binoculars. Other than that, people who live in dry and hot places are not really forced to get one since they can prevent fungal growth by properly cleaning their binoculars.



Ioana Moldovan

Ioana’s professional experience in the optics field has helped her understand the value of passing her knowledge forward. Her curious personality helps her gather useful information for her readers and her goal is to make technical information fun and accessible to everyone.

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Nicholas Cantarella
Nicholas Cantarella
1 year ago

Miss Loano, i’m a 66 yr young rookie at star gazing. I’ve was atracked to the nano technology 300mag 45dia because it also provides smart phone adapter for recording. What hand held telescope magnification is needed to view Celestial Events. TY Protection Status