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Daniel | 31/03/2020
For the uninitiated, binoculars can be a little tricky to get to grips with. With so many models available, all with different specs, how do you choose the right pair? Not to worry- we’re here to clear things up for you. We’ve taken some of the most commonly asked questions about binoculars, and put all the answers in one handy blog post. Read on, and by the end you’ll be a binocular expert!
Related: Top 10 Best Binoculars for Birdwatching
The human eye can see surprisingly far. With no obstructions, it’s possible to identify objects some three miles away. But the further away something is, the harder it is to pick out individual details. Unfortunately, there’s no way to physically train your eyes to see those faraway objects in greater clarity. Luckily, that’s where binoculars can help!
When you look at an object, what your eye is actually “seeing” is the light reflected off it- which is why we can’t see in the dark. If that light passes through a transparent object at an angle, it bends, or “refracts”. The bigger the angle, the more it will refract. Binoculars are built around this principle, using multiple lenses to focus light into your eyes so that you can see faraway objects in greater clarity.
Most binoculars have two parts to their name. The first refers to the particular model, while the second will be two numbers with an “x” in the middle- for instance, “8x42”. The first number refers to the magnification, which is pretty self-explanatory. The higher this number, the more they will magnify the object you’re looking at. Of course, this also limits the field of view, which we’ll come to in a moment.
The second of those numbers refers to the size of the lens aperture. In layman’s terms, that means the diameter of each lens. This affects how much light can get through, and a larger lens aperture generally means a brighter image. Outdoors on a sunny day, most users wouldn’t notice much change between a 32mm lens and a 50mm one. But in less-than-perfect conditions, the lens aperture can make a huge difference. Higher apertures allow binoculars to still give a clear image in cloudy conditions, or at dawn and dusk- two prime times of day for birding. A larger lens aperture does mean that the binoculars themselves will be larger and heavier, though. This is something to bear in mind if you prefer to travel light, or if space is going to be an issue.
“Field of view” describes how far you can see from left to right without moving your head. The human eye has a field of view of about 180 degrees. Naturally, since binoculars are more focused, that field of view is cut down significantly. With binoculars, the field of view is given one of two ways. Some brands express it as a degree- e.g. 7. Others give it as how wide the image will be at a distance of 1km- e.g. 370m.
A higher magnification on binoculars means a smaller field of view. However, the precise field of view can vary from one pair to another, even those of the same brand and magnification. A wider field of view is generally better, as it means you don’t need to be quite so precise when tracking moving objects.
Some binoculars are specially designed to give an extra-wide field of view. However, these generally won’t work with glasses, and some can sacrifice on image clarity. There are more important factors to bear in mind when choosing binoculars, but if you can, try out a few models with different fields of view to find out which one you prefer.
Some higher-end binoculars come with special Extra-Low Dispersion lenses. If you’ve ever seen the cover of Dark Side of the Moon, then you’ll know that when light passes through a lens, it is then dispersed into different colours. The more dispersion that occurs, the more diluted those colours will be, to the point where there is a visible "halo" around the object. ED lenses are made from special glass to keep dispersion to a minimum. The result is a sharper, clearer image.
To further cut down on light dispersion, special optical coatings are applied to the lenses of many binoculars. Without any coating, each lens of your binoculars can lose up to 5% of the light which enters it. Given that binoculars are made from multiple lenses, that means you could lose up to a third of the light entering the objective lens. On the other hand, lens coatings reduce that light loss to as little as 0.5% per lens.
There are several different categories of lens coatings:
Phase coating: Most birding binoculars nowadays use a roof prism design, where the objective lens lines up with the eyepiece. Without going too deep into the science of this, as light passes through roof prism binoculars, it can essentially fold back on itself slightly. By the time the light reaches your eye, it will have fallen slightly out of phase with itself, reducing the brightness and clarity of the image. Phase coating delays this process so that the light remains in phase when it hits your eye. This used to be quite an expensive addition to binoculars, but thanks to advances in technology, you can now find many affordable pairs of binoculars with phase coating.
If you're using your binoculars regularly, they will inevitable pick up some dirt over time. The casing of the binoculars can be cleaned as often as needed. However, you'll need to be careful when cleaning the lenses. If you are too rough with them, you could damage the lens coating and affect their performance. For that reason, you should only give them a proper clean when they really need it.
To clean your binoculars, start by gently blowing off any dirt or dust from the lenses. Ideally, hold them slightly above your head as you do this, so that gravity does a bit of the work for you. Then, take a microfibre cloth, and spray some cleaning fluid onto it- never spray the fluid directly onto the lenses. Use soft, circular motions, and gently clean the lens from the centre out to the edge.
Higher magnification binoculars let you get a clearer image of things that are a long way away. But because they focus on such a small point, the image is liable to jump around an awful lot if you move your hand even slightly. This problem is even greater if you’re using your binoculars from a moving vehicle or on a boat. Even lower-magnification binoculars can be very tricky to use in these circumstances. Luckily, that’s where image stabilising binoculars can help!
As the name suggests, these binoculars use special technology to counteract any movement, so that to the user’s eye, the image remains steady. They sense movement electronically, which means they need batteries to work. Combined with the larger size that comes with higher magnification, that means they can be a little bit heavier than other models. However, this doesn't affect their usability- after all, they are intended for use without a tripod.
Related: Top 3 Best Image Stabilised Binoculars
You might think that even if you’ve got poor eyesight, binoculars will still provide a clear image of whatever you’re looking at. Unfortunately, though, that’s not the case. Binocular lenses are designed with users with 20/20 vision in mind, which means you'll need to wear your glasses while using them. However, unless your eyes are right against the lens, the image from the binoculars won't fill your vision. Instead, you'll get a big black border around it, and only the very centre of the image will be properly in focus.
Luckily, there are a number of binoculars that can be used with glasses. You just need to look out for models with twist-down eyecups. These allow you to get the lenses right up to your glasses, to prevent the issues we just mentioned. It also means others who don't wear glasses can still use the binoculars comfortably.
Put simply, “eye relief” is how far your eye can be from the actual lens while still being able to see the full field of view. For most people, this simply affects how comfortable the binoculars are to use. After all, if you have to keep the eyecups pressed tightly against your eyes, then your eyes will get sore after a while. For glasses-wearers, though, eye relief is much more important. Naturally, you won't be able to press your eye right up against the lens. Again, look for binoculars with twist-down eyecups for the best viewing experience.
Generally speaking, binoculars with higher magnification or a wider field of view will have less eye relief. We make sure to note the eye relief on all the binoculars we sell.
Not necessarily. Yes, higher magnification binoculars allow you to see objects more clearly. However, because they have a narrower field of view, they can make it more difficult to track moving objects. They also tend to be somewhat heavier than lower-magnification models. Novice users may be better off with an 8x pair of binoculars to start with. As you become more practised, you can then move on to a 10x pair.
The quality of the binoculars is down to more than just the magnification, though. Better optics will mean a clearer image, and fully multi-coated lenses provide brighter colours than those with no coating at all. Rather than merely looking at magnification, it's better to start by selecting a good quality brand like Viking or Celestron, and then think about specifics.
Finally, there are some cases where lower-magnification binoculars are actually a better choice. For instance, at sporting events like horse races, you don’t necessarily need to be zoomed right in. Instead, you'll want a wider view of the action. Lower-magnification models are also a better choice for kids, since they are easier to use than a more precise pair of binoculars.
All good-quality binoculars are nitrogen-filled. While the binoculars are being made, they are pumped with dry nitrogen gas under high levels of pressure. This forces out any impurities that might be inside them, and also ensures they are completely free from any internal moisture. They are then sealed airtight, meaning no moisture can get in at all, either.
If there was any moisture in there, then the lenses could fog up from the inside, leaving you with no way of clearing them. This occurs when it’s cold outside- so the chances of it happening here in the UK are pretty high! The only thing to do is to wait for the water to evaporate, which can take even longer if you’re somewhere with high humidity, and could potentially put a damper on your whole day’s birdwatching.
Since the binoculars need to be sealed airtight, this also means no water can get in, either. While not all binoculars will survive being fully submerged in water for more than a few minutes, most of them can survive being used in the rain or the odd splash of water.
Browse our full selection of binoculars and scopes here >
This entry was posted in Binoculars & Birding on 31/03/2020 by Daniel.