Binoculars 101: How to choose your Right Binocular

by: OZScopes - The Australian Telescope Experts

So you've started your journey into the exciting world of binoculars. Maybe you've been thinking if buying binoculars for a while, maybe you're just wondering how binoculars work, or you're just trying to figure out which binoculars are right for you. This guide will attempt to answer all those questions and more!

Choosing the ideal pair of binoculars begins with familiarising yourself with a few technical terms. Together, these basic features will determine how a given pair of binoculars will perform in the field. You'll be able to gather more knowledge about binoculars from reading a binoculars' reviews, and then figuring out which brands are right for you from there - there are binoculars by Vortex, Zeiss, Meade, Barska, Bushnell, Steiner - and the list goes on.In the meantime, this guide will introduce you to the key concepts about binoculars' specifications, and what you should look out for.

Let’s take a closer look at these technical terms and what they really mean:

What do the numbers in binoculars names mean?

Steiner Safari Ultrasharp 8x30 Binocular
Steiner Safari Ultrasharp 8x30 Binocular

The numbers in the name of any pair of binoculars denote the configuration or specifications of that binocular. Let's take the Steiner Safari Ultrasharp 8x30 Binocular for example.

Aside from being a fantastic pair of binoculars, they have a fixed 8x magnification and a 32mm aperture size (lens diameter).

In any binoculars, the numbers that precede the "x" or multiplication symbol refer to the binoculars magnification. The numbers that come after the "x" or multiplication symbol refer to the binoculars' aperture.

Aperture size simply refers to the diameter of the objective lens i.e. the lens in the front of the binoculars that you look out of.


Magnification (Power)

The magnification or power of a pair of binoculars refer to the same thing - the amount of magnification achieved with those binoculars, as opposed to viewing the same object with the naked eye. For example, if you're looking at an object 100m away through binoculars with 10x magnification, the object will seem only 10m away.

Wondering how much magnification you need in your binocular?

You magnification will have to be appropriate to what you need them for - think about the demands of your hobby before you think about buying binoculars.

a) Will you be using them to to see things close up or far away? If you're planning to look into the distance, you'll need high powered binocular or spotting scopes (as opposed to binoculars).
b) How much detail will you need to see? If you need to see lots of intricate detail, think about high powered binoculars with a large aperture size - bear in mind that this will exponentially increase the size and weight of the binocular.
c) Will you be able to prop your arms up on something for support, or will you need something small and compact? If you needed something small and compact, you're best with something with a lower aperture size to ensure that it's lightweight, and a correspondingly low magnification to ensure that you maintain image resolution.

The most popular binoculars are the ones with lower magnifications (such as with 8x binocular). They have wider fields of view - which makes sense, as you see much more of a scene if you're using smaller magnifications. A wide field of view is important when you're trying to follow fast-moving action (i.e. quarry or game on the move; sports), birds on the wing, or athletes at a fast-paced sporting event. As such, think about how much of a scene (or frame) you want to look at a time - it should make a big difference on the pair of binoculars you buy.

Higher magnifications afford you more detail, but are more difficult to hold steady - they amplify every little hand shake by their magnification factor, and you may find that a Tripod is the most convenient way of correcting that.

Vortex High Country Tripod
Vortex High Country Tripod for Binoculars, Cameras and Spotting Scopes

The Vortex High Country Tripod is a good option if you're looking for a sturdy tripod for your binoculars. Binoculars with high magnification also give you narrower fields of view, so you have to decide that image size and detail are factors that you can sacrifice when you purchase a more powerful pair of binoculars, especially astronomy binoculars that featured with high aperture lens.

Objective lens(aperture)

The objective lens is the front lens of the binoculars, measured in (mm) terms. The size (diameter) of its lens determines how much light is gathered, and is referred to as its aperture size. The bigger the aperture, the more light its able to capture, which results in better image clarity. For example, the Vortex Diamondback 10x50 Binocular have better light gathering capabilities than the Vortex Diamondback 10x42 Binocular. Although both binoculars have the same magnification, the Vortex Diamondback 10x50 Binocular produce relatively brighter images, and will provide you with a superior viewing experience.

Here, you can see a good example of the difference in image brightness between a 32mm, 42mm and 52mm objective lens (with equal magnification).

Clarity at 32mm
Clarity at 42mm
Clarity at 50mm
Figure 1.2 Aperture Size and Image Clarity

However, the the larger the aperture size, the bulkier and heavier the binoculars. Although the 8x20 binocular provides less than ideal viewing, but they are smaller and lighter, making them a better choice for those who require more portable binocular.

Remember : The diameter of the objective lens is directly related to the size of the binocular -- the larger the objective lens, the larger (and often bulkier) the binocular. So you've got to toss it up - if you're after portability, you'll sacrifice image resolution and vice versa.

Binoculars Design - Porro Prisms and Roof Prisms

There are several technologies present in the manufacturing of telescopes, and you'll come across them in your hunt for binoculars as well.

There are 2 main kinds of binoculars: porro prisms and roof prisms.They both use image-erecting prisms to provide correctly oriented images.

Porro Prism Binoculars

Bushnell Legacy WP 10-22x50 Zoom Binocular
Bushnell Legacy WP 10-22x50 Zoom Binocular

The Bushnell Legacy WP 10-22x50 Zoom Binocular is an example of a pair of binocular that utilises Porro prisms. Porro prism binoculars are usually recognized as your "traditional" binoculars. They have offset prisms, and are recognizable from their "V" shaped tubes. Reversed Porro prism binoculars, on the other hand, allows for compact binoculars that fit easily into your hands, and they are recognised by their "inverted" tube shape.

The technology utilised in Porro prism binoculars result in binocs that are wide, with well-separated objective lenses, but offset from the eyepieces. They generally provide good depth-perception, because of the way they've been made. Porro prism binoculars occasionally need their prisms realigned to bring them into collimation.

When you buy porro prism binoculars you get the best bang for your buck, but bear in mind that they aren't as durable nor as compact as the stylings of roof prism binoculars (see below). They will, however, generally provide brighter images than roof-prism binoculars of the same specifications because roof prism binoculars utilise silvered surfaces that reduce the transmission of light through its optics.

Roof Prism Binoculars

Bushnell Forge 10x42 ED Roof Binocular Bushnell Forge 10x42 ED Roof Binocular

The Bushnell Forge 10x42 ED Roof Binocular is an example of a pair of binocular that utilises roof prisms. Roof prism binoculars are generally more compact that porro prism binoculars, and have parallel, cylindrical tube stylings, allowing them to both be more compact and durable.

Roof prism binoculars deliver more durability, but tend to cost a bit more to get good optical quality in this design.

Field of View

Field of view refers to the size of the viewing window. Essentially, this refers to the widest dimension visible through your binoculars. Some binoculars will feature unique lenses to provide a "wide field" greater than those normally seen through binoculars of the same magnification.

Barska Focus Free Wide Angle 10x50 Binocular
Barska Focus Free Wide Angle 10x50 Binocular

The Barska Focus Free Wide Angle 10x50 Binocular is a good example of such a pair of binoculars that provide a larger than normal field of view - these binoculars are generally referred to as wide angle binoculars. Wide-angled binoculars are preferred if you're trying to observe at close quarters deep in the woods, or if you were keen on picking up on things that move quickly across your viewing area (think bird-watching).

Note: Field of View decreases as magnification increases, and vice versa. Elect to buy binoculars with lower magnifications if a wide field of view is important to your activity, or purchase wide-angled binoculars instead. Also, large objective lenses (aperture size) provides a larger field of view. Porro prism binoculars also typically provide larger fields of view than roof prism binoculars, given the same specifications.

Eye Relief

Lots of people wonder what they should do if they wear their spectacles or eyeglasses while using binoculars. Most binoculars have been designed to allow for comfortable viewing even with your eyeglasses on, and to do so they provide you with longer eye relief.

Eye relief simply refers to the distance that images are projected from the lens to their focal point, and they vary from 5mm to 23mm. If you're looking for binoculars to use with your sunglasses or spectacles, try to look for binoculars that provide an eye relief of at least 15mm. Note: Without proper eye relief, you won't be able to see the full field of view with your glasses on.

When using your binoculars, be sure you understand how to use your eyecups - all binoculars allow you control over them. There's either a rubber eyecup that can be folded down, or - more commonly - a newer type that twists or slides up and down on the binoculars' eyepiece.

If you wear spectacles or eyeglases and you plan to use binoculars indoors, you'll definitely need to buy binoculars with long eye relief. You'll want to have to binoculars' eyepieces rolled down (i.e. placed down, close to the binoculars) during use. This ensures you see the maximum field of view.

Conversely, if you don't wear glasses, try to leave them fully extended (placed up, away from the binoculars), allowing the eyecups to just lightly touch your face. This helps to block out peripheral light.

Diopter Adjustment

Most better quality binoculars allow you to adjust the focus on one eyepiece (usually the right eye) of your binoculars using a diopter adjuster.

The purpose of a diopter adjuster is to compensate for the differences in your eyes, so you can see the clearest image possible through your binoculars.

To make your diopter adjustment, choose an object to focus on in the distance. Try to pick something distinctive that's past the close focus distance of your binocular, but not too far away.

a) Come to a sharp focus on the object using the center or individual focus of your binocular (with your diopter-corrected eyepiece blocked off/eye closed).
b) Once you've got the image focussed as sharply as possible, close that eyepiece off/shut your eye on that side.
c) Now, open your other eye (on the diopter-corrected side), and without moving the center or individual focus dial, try to improve the sharpness of the image by moving the diopter adjustment.
d) Now that you've found the setting which gives you the sharpest image, note it and leave it - you're done! From here on out, use only the center focus to adjust both eyes while viewing.

Note : You should set your diopter adjuster when you first use your binoculars, and make note of the settings. Check the diopter setting on your binos to ensure they haven't changed, and again after you've shared your binoculars with someone else.

Cleaning your Binoculars

So now that you've got a pair of binoculars of your very own, you're probably wondering how to clean binoculars.

Firstly, always use common sense in the care and maintenance of your binoculars. Attempt to blow off visible dust and dirt before brushing or rubbing anything on the glass lenses of your binoculars.

If that fails, use a lens cleaning tool like a lens pen or lens cleaning tool to gently wipe off any remaining marks or spots from your binoculars lenses. If the marks are stubborn, like dried water spots, remove them by fogging the lens with your breath and wiping it away with micro-fibre cloths.

Note : Do NOT use your shirt tails or tissues to clean your binocular lenses, as they contain fibres that can damage or scratch the coatings on the lenses. After you've bought the perfect pair of binoculars, the last thing you want to do is scratch those beautiful lenses forever!

Try your best to keep your binoculars lenses as clean as possible, free of dirt and oil. The occasional wipe with vinyl and rubber preservatives will extend the life of the rubber eyecupts, and also check yoru neckstraps and attachments from time to time. Looks out especially for wear or slippage - the last thing you want would be your binos to fly off and hit the ground!

Other features

Image stabilization

Carl Zeiss 20x60 T*S Image Stabilization Binocular
Carl Zeiss 20x60 T*S Image Stabilization Binocular

Image stabilization binoculars are designed to counteract the natural unsteadiness of the hand. This self-steadying feature employs gyroscopes and liquid filled prisms which autocorrects for jitters and shakes.

As magnification increases, so does the instability of the image, regardless of how steady handedness the user may be. Therefore, image stabilization is particularly important for binoculars with high magnification. Image stabilization is also valuable for use in unsteady situations, such as when boating, or for long term observations where muscle fatigue can amplify unsteadiness. Hence, with image stabilizers, you can enjoy clearer viewing for a longer period of time.

Focus: Individual vs Center

Center focus binoculars allow both eyepieces to be adjusted simultaneously. This is useful for applications that require fast and frequent adjustments. Center focus binoculars are a popular choice for hunting, birding, and general wildlife observation.

Individual focus binoculars require that each eyepiece be adjusted separately every time you change the focus. These binoculars are good for applications that do not require frequent readjustments, such as boating, surveillance and astronomy.

Example of individual focus binoculars:

Steiner Commander 7x50 Compass Binocular
Steiner Commander 7x50 Compass Binocular

Example of center focus binoculars

Leica Trinovid 8x32 HD Binocular
Leica Trinovid 8x32 HD Binocular

Water Resistance

First of all, you should take note that water resistant and waterproof binoculars are not created equal.

Water resistant binoculars feature tight seals and exterior coatings that offer protection from precipitation, dew and accidental splashes and spills. This is usually sufficient protection for most binocular applications.

Truly waterproof binoculars have features that further enable them to function whilst fully submerged in water (usually up to 5 meters deep). These type of binoculars are a wise choice for boating and/or marine use. When choosing binoculars, apart from users that are frequently in contact with water, it's usually fine to settle for binoculars without neither water resistant or water proof features, since the occasional drops of water does not generally cause much or any damage at all.

Check out OZScopes range of Waterproof binoculars.

Marine Binoculars

Zoom binoculars

Zoom binoculars are sometimes referred to as "variable zoom binoculars" as they allow you to "zoom-in" and "zoom-out" - much like you would with a standard camera. The main advantage of (variable) zoom binoculars is that they are able to achieve multiple levels of magnification, but keep in mind that the size of the objective lens does not change. This means that as you increase magnification, you decrease the diameter of the exit pupil, which results in a dimmer (darker) image. With zoom binoculars, the magnification power is there when you need it, but the resulting images at high magnification will be dim and unstable.

Note : If most of your viewing will be at low magnifications, but you want the option for occasional upclose viewing, zoom binoculars are a practical choice. However, if you plan to use high levels of magnification frequently, consider higher powered binoculars with appropriately sized objective lenses for comfortable viewing.

An important thing you'll need to know about binoculars is that they're actually two independent telescopes connected together.

This sounds fairly primitive, and really, it still is - despite many improvements with technology. Zoom binoculars have to maintain a kind of synchronization between the two scopes, consisting of a moving lens element within each eyepiece. This is generally accomplished by a flexible metal band - known as a "Zoom linkage band" - that passes through the ocular arms to connect the zoom mechanisms on both sides together.

Because of the sheer number of minute, moving parts, it is either impossible or very, very difficult to get both scopes aligned properly. Thus, collimation problems often occur. Each image will shift slightly as the lens elements move, and although this wouldn't be noticeable in a monocular, your binoculars end up never being in "perfect" alignment.

Generally, unless a zoom functionality is very important to you, we recommend that you instead purchase a pair with fixed magnification binoculars. Fixed magnification binoculars will be less versatile when compared to variable zoom binoculars, but it will be more sturdy, and provide you with a far superior viewing experience.

Check out OZScopes range of Zoom Binoculars.
Zoom Binoculars

You may also be interested in: night vision optics and our range of rifle scope or telescopes.