Everything you need to know about binoculars

You need to keep a couple of factors in mind when you want to purchase a pair of binoculars. We have explained which factors are most important to keep in mind, and where you need to pay attention to with the purchase of binoculars. Our expert also gives you advice for the different situations when using binoculars.

The numbers of binoculars

All the binoculars have two numbers in their name, with an x in between, such as 8x42. The first number, in this case the 8, is equal to the magnification: so the magnification is 8x. The second number, the 42, stands for the diameter of the lens in millimetres: so the lens diameter is 42 millimetres. These numbers are one of the most important factors to pay attention to when you want to purchase a pair of binoculars. down below, we give you a more in-depth explanation of these two numbers.

The first number: the magnification

As we mentioned above, you need to pay attention to these two numbers when looking for a pair of binoculars. The first number stands for the magnification. For example, binoculars with 8x42 in the name, magnify the image with 8x. A magnification of 10x is most suitable for safari tours and hunting. For bird watching, we recommend a magnification of 8x so you can easily follow the bird's movements. Most of the times, spotting scopes have a much higher magnification compared to binoculars, so you can observe your binoculars up close.

The second number: the lens diameter

The second number stands for the diameter of the lenses of the binoculars, which are also called the objective lenses. the bigger these lenses are, the more light will be transmitted. This will result in a more detailed image. A high light transmission is very useful for sunrise and sundown. The disadvantage of a large diameter, is the fact that your binoculars tend to be more heavy, which can be inconvenient when you want to carry it with you. When you will use your binoculars particularly for hunting of for a safari, it would be wise to pay attention to the weight.

Types of binoculars

There a two different main types of binoculars: binoculars and monoculars. The names already say it all, as a pair of binoculars has two eyepieces whereas monoculars have one eyepiece. This also means that you can only observe with one eye when using monoculars. Binoculars can be divided into two types: roof and porro binoculars.

Porro binoculars

Most of the time, the porro binoculars are a bit larger and heavier than roof binoculars. this is a result of the difference in light transmission. In porro binoculars, the light travels through an N-shape. This causes the wide shape of the porro binoculars. A pair of porro binoculars are often heavier and less compact than a pair of roof binoculars, which can be a disadvantage of these binoculars. However, porro binoculars are a bit easier to manufacture and are therefore a bit less expensive than roof binoculars.

  1. Often less expensive than roof binoculars
  2. The image of porro binoculars is very in-depth
  1. Relatively big and less convenient to take with you

Roof binoculars

The roof binoculars are often more compact than porro binoculars, as the light travels in one straight line through the binoculars. Roof binoculars are a bit more difficult to manufacture, making them a bit more expensive than porro binoculars. Roof binoculars however, tend to be quite compact and lightweight, making it very suitable for long hikes. Wearing roof binoculars around your neck or carrying them with you is most comfortable.

  1. Compact, so easier to carry with you
  2. Often less heavy than porro binoculars
  1. Since roof binoculars are a bit more difficult to manufacture, they are a bit more expensive

Binoculars for spectacle wearers

Do you wear glasses? The eye relief of binoculars is very important when looking for the right binoculars while you are a spectacle wearer. Most of the people think the eye relief is the distance between your eyes, which is not the case. The eye relief is the distance between the lenses of the binoculars and the place your eyes create the image. For spectacle wearers, it is advised to look for binoculars with an eye relief of at least 15 millimetres. This ensures a comfortable view. Some binoculars have eyecups that can fold down or rotate down, so you can adjust the eye relief yourself. You can decide to observe without wearing glasses: your binoculars will adjust your eyes by focusing on the object.

A spotting scope

You have a different category besides binoculars: spotting scopes. A spotting scopes has some similarities with a telescope, but they are not the same! A spotting scope can be seen as a merge of a pair of binoculars and a telescope. It is often very suitable for large distances. The magnifying factor of a spotting scope is much higher than the factor of binoculars. It is in fact that high, you cannot comfortably use your hands to look through the spotting scope, as this creates a shaky image due to the large magnification and the heavy weight of a spotting scope. Therefore, you should always use a spotting scope in combination with a tripod. Using a tripod ensures a stable and clear image, so you can enjoy your spotting scope to the fullest. The magnification, clarity and depth of the image of a spotting scope will be fully utilised. This way, you can observe birds and nature in great detail for hours.

Types of glass: BK-7 vs. BaK-4

The lenses of binoculars are made of crown glass. These quality can be differentiated between BK-7 or BaK-4. Down below, you can read more about the differences, the advantages and the disadvantages of these two types of glass.

BK-7 glass

The term BK-7 is created by the German firm Schott AG. The glass is made of crown glass and has a high refractive index. A high refractive index ensures a clear and sharp image. BK-7 glass is easier to produce than BaK-4 glass, making it a bit cheaper. BK-7 is mostly used in cheaper binoculars models.

  1. Most used glass in binoculars
  2. Often cheaper than BaK-4 glass
  1. Less high refractive index than BaK-4 glass

BaK-4 glass

BaK-4 glass is made of an even better quality than BK-7 glass. It is made of barium crown glass and has a higher refractive index than BK-7 glass. Therefore, you can expect an even better and vibrant image of a pair of binoculars with BaK-4 glass. Producing BaK-4 glass is more expensive than producing BK-7 glass. This results in the fact that only the more expensive models have BaK-4 glass.

  1. A higher refractive index
  2. Clear edges with a wide field of view
  1. More expensive to produce

Field of view

The field of view defines the width of the image you see through your binoculars at a distance of 1000 meters. For example, when you have a field of view of 125 meters at 1000 meters, this means you observe a width of 125 meters through your binoculars. Often, you have a narrow image with a higher magnification. A broad field of view creates a stable image, which enhances the comfort of observing. A broad field of view allows you to easily follow the movements of an animal, such as birds.

The Twilight factor

The twilight factor defines the performance of a pair of binoculars in an environment with not so much light, such as dusk or dawn. To use a pair of binoculars in the twilight, the binoculars need a twilight factor of at least 15. When the binoculars have a lower twilight factor, you can only use them during daytime. When the twilight factor is higher than 15, the binoculars are more suitable to be used in twilight.

When you need binoculars to watch birds, you need to ask yourself when you want to do this. Will you only spot birds during daytime, when the sun is out? then you do not need a pair of binoculars with a high twilight factor. However, when you also want to observe the birds during sunrise and sundown, when they are most active, you will need a pair of binoculars with a twilight factor of at least 15. This advice can also be applied when you are looking for binoculars when you go on a safari: most wild animals are very active in the morning or evening, when the sun is not so bright.

The formula for calculating the twilight factor is as follows:
Twilight factor = √ (magnification x lens diameter)

For example: you have a pair of binoculars of 8x42. 8 x 42 = 336. √336 = 18,33. The twilight factor is higher than 15, making these binoculars suitable to be used during dusk and dawn.

The exit pupil

The exit pupil is the diameter of the light that comes from the eyepiece. When you use the binoculars in an environment with not much light, it is comfortable to have a large exit pupil. A smaller exit pupil works perfectly when you observe during broad daylight. You can calculate the exit pupil by divide the diameter of the binoculars by the magnification.

The formula for calculating the exit pupil is as follows:
Exit pupil = (lens diameter / magnification)

For example: a pair of 8x42 binoculars has an exit pupil of: 42 / 8 = 5,25. These binoculars can also be used in dusk and dawn.

The coating

A coating can be defined as a layer over the lens of binoculars. This coating enhances the quality of the lenses of the binoculars. As a result, a coating can diminish the reflection, and can enhance the light sensitivity. This allows you to also use the binoculars in the twilight. A coating can also enhance the colours, ensuring a vibrant image. When you use binoculars with a coating, it might be wise to not touch the lenses with your fingertips. The acid in your skin can affect the coating.

You have three main types of coating for binoculars: coated, multi coated and fully multi coated. When you binoculars have coated lenses, one of all the lenses have one layer of coating. Binoculars with multi coated lenses, have lenses which all have one layer of coating. Fully multi coated lenses are lenses which all have multiple layers of coating. Often, more expensive binoculars have multiple layers of coating.

How to take care of your binoculars

When you take care of your binoculars, they will last you for years or even a lifetime. To enjoy your binoculars for life, it is important to keep the following advice in mind.

Never place your binoculars directly in the sun! The glasses of the lenses function as a magnifying glass, which can melt the interior of binoculars. This can do great harm to your binoculars. Therefore, keep your binoculars out of the sun and store them by using protective caps and a carrying bag. Also, do not leave your binoculars onto the dashboard of your car, since it can easily get very hot inside!

A lot of binoculars are waterproof. However, do not store your binoculars away while they are still wet. Always dry your binoculars carefully with a soft cloth, before you store them. The best thing to do, is to dry it for a couple of minutes at room temperature, before you store it.