The good weather arrives and this increases the desire to go out and enjoy nature. You may want to observe all kinds of animals (birds, mammals, reptiles, etc.) in your habitat while taking a long walk in the countryside or mountain. To do it quietly and without disturbing the animals, it is best to use binoculars and look from a distance.

This is not the only activity you can do with the help of binoculars. These gadgets are also very useful in a concert or a sporting event. In both cases, you may be away from the scene and some binoculars can help you capture more details. Astronomy is another activity where they can be very useful. Or, if you are the type that like sailing on a yacht by the sea or in a canoe by the river, these piece of gadgets can also be helpful. As you can see, binoculars serve different activities very different from each other.

The question is, how can you choose the best binoculars for the money that best fit your needs? For this, you will have to be able to unravel the mysteries that hide the numbers that appear in the box, which refer to the technical characteristics. Keep reading and you will see that it is not so difficult and that you yourself will be able to choose the ones you need.

  1. Magnifications

The main function of binoculars is to enlarge what is far away so that we can see it better. After all, they are two small telescopes placed next to each other. For this reason, it is vital to know the increases that it provides. The increase is the degree of magnification of the observed object and is defined by a number, the first of which defines the binoculars and are separated by a blade.

In this way, if the box says that they are binoculars 7×42, the 7 refers to the increases. These binoculars extend the object observed to seven times with respect to human vision. If the number is 10×50, the magnifications are 10. To observe the nature, you will need binoculars with 7, 8 or 10 magnifications.

From 12x magnification, you may also need a tripod because the size of the device will be larger and will weigh you, which will cause vibrations when using it by a pulse. It will depend on your strength. Of course, from 20 increases you should buy a tripod. For the theater, a concert or a sporting event do not need so many increases. Even with 3x binoculars, you can see everything without problems.

Sometimes binoculars have two numbers before the blade. For example, 8-24×50. This happens with variable magnification models. Thanks to its internal mobile configuration, we can have from 8 to 24 magnifications using, yes, only the body of one of the two binoculars. Very useful if you want to use the device for several different activities.

A final note before moving on to the next section. The degree of magnification affects the brightness of the image. How? The smaller the magnification of binoculars, the brighter the observed image. Also, as I will explain later, it affects the field of vision. The greater number of increases, the less field of view.

  1. The diameter of the objective lens.

The second of the two main numbers that define the binoculars refers to the diameter of the objective lenses, which are those located on the front, the furthest from the eyes. That diameter is expressed in millimeters. For example, 8×50 binoculars are fitted with objective lenses of 50 millimeters in diameter. Some 7×35, 35 mm.

It is important that you know what the diameter of the target lens affects. First, the size of binoculars. A larger lens involves a larger size of the set and also an increase in weight. Second, the diameter determines the light pickup of the binoculars. The larger the diameter, the brighter and more detailed you will see the image.

Given this information, you probably think that it is best to bet on binoculars that have many increases and a large diameter of the objective lenses. It seems logical, but beware that is not accurate if we want to perform the observation in low light conditions.

  1. Relative brightness.

Relative luminosity is also known as relative aperture, relative brightness index or simply luminosity. It is a value that indicates the performance of binoculars in low light conditions. It is calculated by dividing the diameter of the target lens by the number of magnifications. Some 10×50 binoculars have a relative brightness of 5. Same as others that is 8×40 or 7×35. In contrast, in 8×50 binoculars, it will be 6.25.

According to the relative brightness scale, it is low when its value is less than 3.5. Between 3.5 and 4, relative brightness is normal, while between 4 and 5 is considered good. From 6, it is considered very well. Binoculars with a brightness of more than 4 are considered luminous and therefore, suitable to observe in low light conditions.

  1. Exit pupil and eye relief

The other parameter that should be taken into account to know if binoculars are suitable for situations of low light is that of the exit pupil. This feature refers to the beam of light emitted by the eyepieces of the binoculars, which are the lenses closest to the eyes. It is expressed in millimeters.

A wide exit pupil helps observation in low light conditions because the larger the pupil of exit, the brighter the observed image is seen as more light reaches the eyes. It is calculated in the same way as the relative luminosity, dividing the diameter of the objective lenses by the number of increases. The result is the same.

Although the human eye can dilate from 2 to 7 millimeters depending on the available light, it is normal that it does not make more than 5 millimeters. That is why it is understood that a pupil of an exit of 5 millimeters is the ideal one.

If it is smaller, observing through binoculars may be uncomfortable. On the other hand, if it is greater, we will waste part of the light that comes to you through the binoculars. Especially during the day, while it would be fine at night because our pupil would dilate more.

Eye lenses should be placed at a comfortable distance from the eyes, and more so if glasses are worn. At that distance is called eye relief. It is the distance necessary for the diameter of our pupil to equal that of the pupil of exit. If they coincide, we will see the whole visual field illuminated.

Typically, the distance of eye accommodation ranges from 5 to 20 millimeters. It is comfortable starting at 10 millimeters, although if you wear glasses it is better than the ‘eye relief’ is 15 millimeters. The lower the distance of the 10 millimeters the more eye strain the user will suffer.

  1. Field of view.

The field of view is defined as the width of the visible area through the binoculars at a distance of 1,000 meters. It is measured in meters although sometimes it can come defined in feet. In that case, it refers to a distance of 1,000 yards (915 meters).

Sometimes it can come expressed in degrees, but then we speak of angular field of vision or angle of vision. In this case, we do not expect to find more than 10 degrees of angle. Normally, it oscillates between 6 and 8 degrees.

The higher the number of magnifications, the smaller the field of view. That is, 16-magnification binoculars have a smaller field of view (about 70 meters) than 10-magnification ones (about 100 meters), which in turn are less than 8 magnification (about 130 meters).

What is the use of a larger field of vision or a smaller field of vision? To observe animals in nature, for example, you will need a greater field of vision, especially if the animals are in motion. You will cover a wider ‘horizon’ width and it will be more difficult for the animal to escape your sight. If you want to know more visit this site

  1. Quality of optical elements.

Binoculars are composed of three optical elements: objective lenses, eye lenses, and prisms. The latter is responsible for transmitting and deflecting the light between the two types of lenses, and also put the image in the correct position. The latter achieve this thanks to the principle of total internal reflection.

According to these prisms, binoculars are divided into two types :

Porro Prism: they owe their name to the Italian engineer Ignazio Porro. Its prisms are placed in a non-linear fashion. For this reason, its external appearance is very characteristic when not being aligned with the ocular lenses and the objective lenses. With these prisms, you have a better perception of depth. The focused object on the background is best distinguished.

Roof Prisms: also called compact, because the prisms are alienated. In this case, the lenses are also aligned, hence their more compact external appearance is characterized by their straightness. Equal quality but is more expensive than porro. On the contrary, they are lighter and manageable to equal size of the lenses.

  1. Prism quality.

Once this differentiation of the different optical elements is established, the important thing is its quality. As for the prisms, they can be plastic (organic) or glass (minerals). The former is cheaper, but their quality is worse. For this reason, it is better to buy binoculars that have glass prisms. Within these, there are two types: BK7 (borosilicate) and BAK-4 (barium crystal).

BaK-4 prisms are more expensive and also offer higher quality because they have a higher refractive index, which results in a brighter image, and also provide sharper images.

  1. Lens quality.

Not only must we talk about the quality of the prisms, but also important to look at the lenses. As in the case of prisms, the best lenses are those of glass. For this reason, it is preferable to use a model that has these lenses and not others of plastic except to be mountaineering or some similar activity. Plastic lenses are more resistant and durable.

To avoid reflections and loss of light, and therefore to achieve clearer and brighter images, the glass lenses have a coating. This coating is not the same in all models, hence there is a classification:

Uncoated: No optical surface has been treated. This causes a lack of contrast and annoying glare that makes observation impossible.

Coated (C): One or more surfaces are treated. It improves quality, but quality remains low.

Fully Coated (FC): All air-separated surfaces are treated with a layer of anti-reflective magnesium fluoride (MgF2). Binoculars transmit 80% of the light, which is an acceptable result.

Multi-Coated (MC): At least one of the surface is treated with multiple layers of a chemical compound. The rest of the surfaces, with Magnesium Fluoride.

Fully Multi-Coated (FMC): All air-separated surfaces are treated with multiple layers of a chemical compound. In this case, the binoculars offer a transmission of 90 to 95%, which gives a very luminous image and with a great contrast.

  1. Focus.

Binoculars have a mechanism that allows you to focus objects at different distances. Usually, it consists of a center wheel, but some models have a system similar to the zoom of the cameras. Regarding the minimum focus distance, the smaller the distance, the better. 8 meters away is a good minimum focusing distance.

Some models do not have a focus wheel. So how do you focus? One quality of human eyes is that we do not see both of us equally well. This happens to everyone, not just those with diopters. Can you fix this with a good pair of binoculars? Yes. Most have a diopter corrector system. How is it used? First look only at the left eyepiece with the left eye and focus with the center wheel. Then, you only look with the right eye and you use the corrector of the right eyepiece.

  1. Waterproof.

If binoculars are waterproof (water resistant), this means it can withstand brief exposure to water. Much better is the protection if it can be qualified as waterproof. In that case, and according to the US Military Specifications, binoculars have to withstand a dive 2 meters deep for two weeks without the water seeping into them.

Water-resistant binoculars are useful in conditions where they can become quite wet as a result of poor weather conditions. The impermeable to water is convenient if you are making a descent down a river or going skiing.