Fogproof & Waterproof Binoculars
These days many binoculars are advertised as being either waterproof, fogproof or both and then there are some that are described as being weather protected or weatherproof, are these all the same and if not what is the difference?
In this guide I will explain what water and fog proofing means, how they make them, do you really need it and list my reviews of some the best fog and waterproof binoculars available.
Waterproofing
Fully waterproof binoculars and spotting scopes are completely sealed internally. This is almost always achieved by using one of the most ingenious, yet simple seals ever developed, the O-ring, which ensures that there is an air and watertight barrier between the lenses, focusing mechanism and the chassis of the binocular.
These seals will prevent any moisture as well as any dust and other small debris from getting inside the unit.
Do you need waterproof binoculars?
If you only use your instrument when the sun is shining, it is only natural to ask “do I need waterproof binoculars?”. My answer to this would still be yes you do and here are the reasons why:
1) Having a waterproof (fully sealed) binocular does not only prevent water from entering the interior, but it will also act as a barrier against dust and other small particles that can end up ruining your view. This is especially important in dry, dusty environments, but also helps if you store them out over long periods, where dust could potentially be a problem.
2) Even though you never take your binoculars out in the rain or even mist, there is still moisture in the air. Whilst this will most probably not immediately affect your optics if you subject your instrument to rapid temperature changes (like taking them out of your warm house into the garden in winter), this can cause any moisture inside your optics to condense or mist up on the inside lens surfaces. Note: As you will read below, most fully waterproof binoculars have the internal air replaced with a dry gas for extra fog protection.
3) If you ever find an old pair of optics (camera, telescope or binocular) in an antique store, you will quite often find a green fungus has grown and attached itself to the inner surface of the lenses. The dry moistureless internal environment of a fully sealed binocular inhibits the growth of molds or fungus and prevents this.
Weatherproof vs Waterproof
This is something that I get asked quite frequently and the confusion is mostly because the term “waterproof” is used a bit too loosely and because there are different degrees of waterproofing.
To be “water-proof” it implies water cannot enter, however, this statement is not qualified and something that is water-proof at normal atmospheric pressures at sea level, for example, may not be when the pressure increases (or indeed decreases). So a binocular that is marketed as being fully water-proof should qualify this by explaining just how waterproof they are, such as to a given depth of immersion and or for a specified period of time. However whilst they may have to demonstrate this to a standards board, it is not always displayed within their marketing material.
But even they don’t quantify it, we can assume that a waterproof device can be fully immersed under a little water for a short period of time, which should cover most reasonable uses for a standard bin.
If a binocular is described as being weather-proof, weather protected or water-resistant they are almost certainly not fully waterproof to any depth even for a short period of time. They do however have some resistance to water and thus should survive light rain, but are not intended to be fully, or even partially immersed in water. Please note that because these water-resistant products are not fully sealed, they are also not fog proof in any way.
If you think that you will need to use your binoculars in a wet environment, make sure that they are 100% waterproof and better still look for ones that advertise just how waterproof they are. Also look out for any standards, for example, the JIS Waterproof Scale, which will describe just how much water your device can take.
Fogproofing
When exposing an unprotected optical device to rapid temperature extremes, especially where there are high levels of humidity, the lenses can fog or mist up, which can at best be a temporary annoyance or at worst permanently ruin the view through them.
To protect against this the air inside the optical barrels is replaced with an inert gas that has no moisture content and thus does not condense. The gas that is used is almost always either nitrogen or argon.
The good news is that today, even fairly inexpensive binoculars and scopes are both waterproof and fogproof.
When reading about binoculars and scopes, you will often come across the term “nitrogen-purging”, which describes the actual process as O2 (oxygen) is removed or purged from the inside of the barrel(s) and replaced with nitrogen.
Obviously to keep the gas inside the chassis, they have to be fully sealed and that is why a fogproof binocular will almost always also be waterproof. But a pair of binoculars can be waterproof without being fogproof. This merely means that the instrument is sealed, but the oxygen inside the barrels haven’t been purged and replaced with an inert gas.
Another point to note is that fogproof binoculars are protected against the fogging up of the internal lens surfaces and not the exterior ones. The advice if the outside surface of your lenses do fog up when taken from a cold to a warm and humid environment is to just allow them to slowly adjust back to the warmer conditions. Do not wipe the condensation off with any old cloth as this may damage your lens or it’s coatings and the condensation will probably reappear anyway.
Nitrogen vs Argon
I have read a number of debates on the web regarding the respective merits of Nitrogen versus Argon gas for fog proofing and it is actually quite hard to separate the hard facts from the marketing hype.
On the one side, I have read some reports that state that because the Argon molecule is larger than the Nitrogen one and can sustain its attributes over a broader temperature range, it is thus said to be more resistant to diffusion or leaking out of the device and so prolongs the life of this air-free environment.
Whilst on the other side, I have read that Nitrogen, Argon, or indeed any other nonreactive gas works as good, not better and the really important bit is that it is a dry gas. Remember that the air in our atmosphere is actually mostly nitrogen (78%) anyway.