Buying guide for binoculars

For anyone involved in outdoor activities, good binoculars are essential. Whether you're into astronomy, birdwatching, hunting or just enjoying the scenery, nothing beats the portability and versatility offered by binoculars.

However, there are many different types of binoculars, and not all of them are suitable for all activities. In this guide, we'll help you understand the different features you need to look for, and give you some tips to make sure you choose the right binoculars for your preferred activities.

Let's start with the basics.



Magnification and aperture

Although there are many different models of binoculars, they all have one thing in common: they are always referred to by their magnification and aperture.

For example, you've probably heard of 10x50 binoculars. The first number stands for the magnification, the second for the aperture, measured in millimeters.

In this case, 10x50 binoculars have a magnification of 10x and an aperture of 50 mm.

This is of course very important information to know, but understanding how magnification and aperture affect the performance of your binoculars is just as important.

Magnification

The concept of magnification is quite simple: it describes the enlarged size of an object when viewed through binoculars. A magnification of 10x will obviously make your target appear ten times larger. However, such magnification is not always appropriate.

Take note: higher magnification will make it harder to locate and track your target. Binocular magnifications generally range from 6x or 7x to 25x, with the lower magnifications providing a better view of the environment.

This makes it easier to locate your target, as you can use a nearby object as a reference point. For example, your target may be perched at the top right of a distant tree. At 6x magnification, the tree and target can easily be seen in the same field of view, but at 20x or 25x magnification, you'll need to find the tree first, then move your binoculars until the target appears.

Aperture

When we talk about the aperture of binoculars, we're talking about the diameter of the lenses that point at your target. These lenses are called objectives and, on traditional Porro prism binoculars (more on that later), these are the large lenses. The small lenses are the eyepieces through which you look.

Aperture can affect the performance of your binoculars in two ways.

Firstly, the larger the aperture, the more light the binoculars can gather. If you want to use your binoculars at dusk or at night, for birdwatching, hunting or astronomy, for example, this will enable you to see more detail and obtain a more vividly colored image, which would otherwise be difficult to see with the naked eye.

This can be particularly important in astronomy, as binoculars with a wider aperture will enable you to see more stars and observe less bright objects. For example, suppose you have three different binoculars - one pair in 10x50, a second in 20x50 and a third in 20x75 - and you use them to observe the Pleiades star cluster.

The 10x50 binoculars already offer a very fine image. The 20x50 binoculars will make the star cluster appear twice as large, but as the aperture is the same, you won't see any more stars. In other words, the extra magnification doesn't allow the binoculars to gather more light.

With 20x75 binoculars, on the other hand, not only will you be able to see the larger star cluster, but you'll also see many more stars, giving you a better overall view.

The second way in which aperture affects performance is weight. Larger aperture binoculars weigh more. On average, 70 mm apertures weigh 1,500 g, around twice as much as 10x50 binoculars.

All cameras with an aperture of 70 mm or more should be mounted on a tripod. Without one, the view can be very unstable and your arms will quickly tire.

As a general rule, 10x50 binoculars are the best choice for general use, for both daytime and night-time observation.

Bushnell

Prism configuration

If you intend to use your binoculars for an extended period and/or use them in different locations when outdoors, you'll have better time to opt for a lightweight solution. This is where binocular prism configuration can play a significant role.

Traditional binoculars have a W or M shape and are known as Porro prism binoculars, but depending on the size of the aperture, they can be a little heavy. Roof prism binoculars, on the other hand, are designed to be compact and lightweight, and are easily identified by their distinctive H-shape.

The choice really depends on your intended use. Roof prism binoculars are relatively light, but their smaller size usually means a smaller aperture and lower magnification. Image quality may also be slightly inferior to that of their Porro prism counterparts.

In this case, roof prism binoculars are ideal for daytime activities such as hiking. On the other hand, their smaller aperture means they are less suited to astronomy or any other hobby that requires good vision in the dark.

Kite Optics En toit Steiner Porro

Field of vision

The field of view is the width of the area you observe through the binoculars. Obviously, higher magnifications usually produce a smaller field of view, but it's also worth noting that larger apertures will have the opposite effect, as the objective lenses will be wider.

For example, you may have 10x20 and 10x50 binoculars. They both produce 10x magnification, but 10x50 binoculars generally offer a wider field of view.

Field of view comes in two types of measurement: linear field of view and angular field of view. This information is normally printed next to one of your binoculars' eyepieces.

Linear field of view

Linear field of view is measured either in feet observed at 1,000 meters, or in meters observed at 1,000 meters. For example, the Zeiss Conquest HD 8x32 binoculars have a linear field of view of 140 meters at 1,000 meters. In other words, the width of the field of view is 140 meters from 1,000 meters.

So if your target was 140 meters wide, it would correspond to the entire field of view at a distance of 1,000 meters.

The same binoculars have a linear field of view of 161 metres at 1,000 metres. A target 161 metres in diameter would therefore correspond to the total field of view at a distance of 1,000 metres.

Fortunately, it's relatively simple to convert the linear field of view from feet to meters and vice versa. To convert feet to meters, divide by three. To convert meters into feet, multiply by three.

Angular field of view

The linear field of view is suitable for observing terrestrial targets, but if you're an astronomy enthusiast, the angular field of view will be much more useful. This describes the number of degrees of sky you can observe with your binoculars.

The Zeiss Terra ED 8x32 binoculars have an angular field of view of 9.2 degrees. This is worth knowing, especially when you consider that the full moon covers about half a degree of the sky. In theory, the field of view of these binoculars can accommodate 18 full moons.

What's more, one degree corresponds to 17.5 meters at 1,000 meters. To convert the angular field of view into a linear field of view, simply multiply the angular field of view by 17.5. To convert linear field of view (in metres) to angular field of view, divide by 17.5.

Since field of view depends on both magnification and aperture, most people find that 10x50 binoculars offer a good balance between the two.

On average, 10x50 binoculars offer a field of view of 307 feet at 1,000 meters, or about 117 meters at 1,000 meters. This also gives an angular field of view of six and a half degrees.

Prismatic lens type

There are two main types of prismatic lens: BK-7 and BAK-4. BAK-4 glass prisms produce a better image, as they are better at retransmitting light (resulting in brighter colors and greater detail) and are better at producing a sharp image.

BK-7 prisms are generally used in low-cost binoculars. If you need daytime viewing binoculars for general use, and cost is an important factor, BK-7 prisms will do just fine. However, if image quality is important, or if you intend to use the binoculars in low-light conditions (for example, for birdwatching or night hunting, or for astronomy), BAK-4 binoculars are the best option.

Optical coatings

Nowadays, the optics (lenses and prisms) of almost all binoculars are coated to improve image quality. At the very least, the coating is designed to improve light transmission, with some coatings reducing reflection and others reducing the transmission of UV light to the eyes.

The type of coating applied should be mentioned alongside any other specifications and will usually be one of the following:

• Single coating (C): at least one of the optical elements (e.g. the objective lens, the eyepiece lens or one of the prisms) has been coated on at least one of its surfaces.
• Multilayer coating (FC): all faces of the optical elements have been covered with at least one coating.
• Full multi-layer coating (FMC): all faces of the optical elements have received several layers of coating.

Generally speaking, full multi-layer coating (FMC) is considered the best, but depending on the manufacturer and the type of coating applied, multi-layer coating (MC) may also be sufficient.

Ocular clearance

Eye Relief is the distance you need to maintain between the eyepieces and your eyes to get the best possible view from your binoculars. If you intend to spend a lot of time looking through your binoculars, you need to take this into account, as insufficient eye relief can result in inferior image quality and eyestrain.

Most binoculars have an eye relief of between 15 and 18 mm, and those with a shorter or longer distance can produce an inferior image, the most common problems being blur and black ring around the view.

Exit pupil

The exit pupil is the diameter of the image projected by the binoculars. As a general rule, the larger the exit pupil, the brighter the image, which can be important if you wish to use the binoculars at night or in low-light conditions.

Calculating the exit pupil is simple: simply divide the binocular aperture by the magnification. For example, 10x50 binoculars have an exit pupil of 5 mm, while 7x50 binoculars have an exit pupil of 7.1 mm.

In this example, 7x50 binoculars would be a better choice for low-light conditions or night-time use.

However, things are a little more complex than that. Depending on age and other factors, the pupil of the human eye has a maximum dilation ranging from 4 to 8 mm. The younger you are, the more your pupil can dilate.

In daylight, the pupil opens to around 3 mm, while at night, adults under 25 see their pupil dilate to around 7 mm, a figure that decreases with age.

This being the case, if the exit pupil of your binoculars is larger than the maximum dilation of your eyes, some of this light (and the resulting image) will be lost.

Other factors to consider

In addition to the key factors mentioned above, there are a few other details worth considering:

Interpupillary distance (IPD): this is the distance between the center of the two eyepieces, which corresponds to the distance between your eyes. You can adjust this distance by gently pulling on the barrels to widen the distance between them. However, incorrect adjustment of the IPD can lead to image loss and eye fatigue.

Environmental protection: many binoculars today feature environmental protection, which can include water resistance and waterproofing, anti-fogging for lenses and a tougher housing to protect against shocks and drops. You'll also find lenses that protect your eyes from ultraviolet rays.

Close focus: the close focus, or focal length, of binoculars indicates the minimum distance at which the target must be in focus. This factor is generally related to magnification. Lower magnifications allow you to focus on closer objects. For example, binoculars with 8x magnification will normally be able to focus on objects at a distance of 2ml or more.

Image stabilization: If your hands tend to shake, or if you need to enjoy a stable view when you're on the move, binoculars with image stabilization may be a good choice for you. The downside? These models are often very expensive!

Night vision: night vision goggles can be particularly useful for hunting. Most work by illuminating the surrounding area with infrared light, which can then be detected and displayed on a screen built into the goggles themselves. Although they generally offer limited magnification (depending on the range of the infrared light), night vision goggles have become increasingly affordable in recent years. Our night vision range.

Conclusions

There are many factors to consider when buying binoculars. But keep in mind the following key points:

• Higher magnification alone does not guarantee a better view
• Wide-aperture binoculars (usually with Porro prism) are better suited to night-time use.
• Smaller aperture binoculars are more suitable for daytime use
• Roof prism binoculars are a good option for those on the move (for hiking or hunting, for example).
• Porro prism binoculars are best suited to activities where you can stay in one place for some time (e.g. birdwatching or astronomy).

Finally, as a general rule, only buy products from reputable manufacturers, such as Nikon, kite Optics, Steiner, or Zeiss, to name but a few. Also bear in mind your intended use, as it's worth choosing a brand that specializes in the type of equipment you're looking for. For example, Zeiss for astronomy or Vortex for hunting.

The good news is that you don't have to spend a lot of money to buy quality binoculars. By following these tips, you'll be sure to find a model that will give you many years of enjoyment. And, of course, you can always count on binoculars.com for the best reviews and recommendations.