Buying Guide: Binoculars

Buying guide: how to choose the right binoculars

You are about to buy a pair of binoculars, but where do you start? We will help you on your way. We have listed the 3 most important types of binoculars and selected the ideal pair for each use case. This is how you choose the binoculars that suit you best.

Types of binoculars

Roof prism binoculars

Roof prism binoculars are compact because the two objective lenses sit directly behind each other. Thanks to the internal focusing system, this type of binocular is less sensitive to dust, water and dirt, meaning it lasts longer.

Porro prism binoculars

Porro binoculars have offset barrels because the prisms and lenses do not sit directly opposite each other. This gives you more depth perception and a clearer distinction between the subject and its surroundings.

Monoculars

A monocular has a single eyepiece and objective lens, so you observe with one eye only. The compact format makes them easy to take along. Judging depth is somewhat harder than with a two-prism binocular.

Which binoculars for different activities?

If you spend a lot of time in nature or on the water, it is important that your binoculars are waterproof and dustproof. Love birdwatching? Then a high magnification factor is important. Do you like going out at night? Then light strength and twilight factor matter most. Whatever you need the binoculars for, there is always a suitable option. Read on to find out which binoculars match which situation.

Events

At festivals, theatre performances and sporting events, crowds and distance can make it hard to see clearly. With binoculars you can bring the stage or football pitch closer. With a magnification of 2x to 10x you can fully experience a theatre show or concert. Porro binoculars are ideal for this purpose.

Travel and nature

Travel and nature enthusiasts know that it is not always easy to observe distant animals or buildings clearly. It is safer to watch dangerous animals from a suitable distance, making binoculars with a magnification factor of 8x to 10x very suitable. A sturdy, waterproof and dustproof compact binocular is important when travelling. For outdoor activities, roof prism binoculars are the perfect choice.

Everyday use

If you regularly want to bring objects or text closer in daily life, a monocular is ideal. Thanks to their compact format they are easy to carry around. We therefore certainly recommend a monocular for everyday activities.

The properties of binoculars explained

There are quite a few terms and values associated with binoculars. But what do they all mean? We will explain the most important properties.

Magnification factor and objective diameter

When buying binoculars, you will see two numbers in the description (e.g. 7x50 or 10x42). The first number is the magnification factor — how many times the image is brought closer. With 7x magnification and an animal at 70 metres, it appears as if it is only 10 metres away. The second number is the objective diameter. The larger this number, the more light enters the binoculars. For use in low light, a larger diameter is advisable. The advantage of a smaller diameter is that those binoculars are more compact and lighter.

Exit pupil

The exit pupil refers to the size of the opening through which light falls onto the eye. The larger it is, the more light enters. The human eye pupil ranges between 2mm and 7mm (older people: max. 5mm) — for night use, choose an exit pupil of around 7mm. For daytime use a smaller opening is sufficient. Calculate the exit pupil by dividing the objective diameter by the magnification factor. With 7x50 binoculars the exit pupil is 7.15mm.

Twilight factor

The performance of binoculars in poor light is often expressed as the twilight factor. The higher this number, the better the performance. Calculate it by multiplying the magnification factor by the objective diameter and taking the square root. For 7x50 binoculars this gives 18.7. Multiply by ten for the maximum distance at which you can still distinguish details — in this case 187 metres.

Light strength

Light strength determines the brightness of the image delivered to the user. The higher this number, the brighter the image. Calculate it by multiplying the exit pupil by itself. With an exit pupil of 7, the light strength is 49. A light strength above this value is only suitable for night use.

Eye distance and field of view

Eye distance is the distance between the lens and the point where the image is formed. For spectacle wearers, a minimum of 15mm is important. The field of view figure is determined by the width visible at 1 kilometre distance. A larger field of view is important when tracking moving objects such as birds without having to constantly adjust the binoculars.

Coating

Coating is essential for binocular quality. A coating is a thin layer applied to the lens that prevents light reflection, improving image quality. There are also separate coatings that protect the binoculars against moisture and dirt.

Quality glass

For the lenses and prisms of binoculars, the quality of the glass determines the final result. The cheapest types are BK7 and BaK-4 glass, which have limitations in low-light performance. SK15 glass is a better choice, as it reduces reflections and delivers a clear image in a wide range of conditions.