Main Factors to Remember When Buying Binoculars

So you know that you want to buy binoculars but you just don’t know where to start? We know that choosing binoculars can be a daunting task as there’s just so many types of binoculars on the market in New Zealand. Our handy binoculars buying guide will help you to understand the basics of buying binoculars and make choosing the right binoculars a breeze.

What Are Binoculars and How Do They Work?

Binoculars are a type of sports optic that’s used to help you see long distances. Built with a metal chassis for strength that creates two barrels, and lenses and prisms, binoculars use optics to magnify the world around you and allow you to view things in more magnification than your naked eye can. The front, objective lenses of binoculars take in light, and the internal prisms and lens coatings reflect the light within the binoculars to direct it to your eyes so that you can see bright, clear images through them. On the way through the barrels, the image you see if magnified to a certain extent before it reaches your eyes. Binoculars are similar in design to a number of other optics such as spotting scopes and monoculars, however they differ in that they have two barrels rather than one, and are best held with two hands rather than on a tripod or with one hand.

Binoculars are a great piece of equipment for any situation where you need a closer view of objects that are a distance away. Whether you want to get a closer look at a bird, boat, animal, mountain, aeroplane, football player, racehorse, butterfly, literally anything at all, then a binocular will help you do that. Due to their relatively compact size and ease of use, binoculars are easy to transport either around your neck or in a bag or backpack so they’re a great optic for use on the move.

Understanding Binocular Optics

Before purchasing some new binoculars, it’s important to have a clear understanding of how the different types of binoculars on the market differ and how to choose quality optics in the best price bracket. To do this, you’ll need to understand binocular specifications and how to read these so that you can compare the differences between the different binoculars and see what offers the best features and value for money.

Key Binocular Features

Let’s take a look at the key features that you should consider when choosing binoculars and how these differentiate one binocular from another. 


Binoculars are available in a range of magnifications which make them particularly suitable for a certain application. In general you’ll find binoculars with a fixed magnification of either 7x, 8x, 10x or 12x. This means that the binoculars offer a magnification that is either 7x, 8x, 10x or 12x that of your naked eye. If you need more magnification than this, or a zoom magnification range then we’d suggest opting for a spotting scope instead. There are a few zoom binoculars on the market but they’re few and far between. All of the binoculars on our website include the magnification of the binoculars in their title and once you understand binocular numbers, it’s easy to decipher what magnification they offer. When reading any binocular name or title, the magnification is the first number you read. So the magnification of the Bushnell H2O 2 10x25 Roof Binoculars is 10x that of your naked eye. The magnification of the Vortex Diamondback HD 8x42 Binoculars is 8x. The magnification you choose should be dependant on the outdoor activity you’re going to use them for and how close you’re going to be to your subject. We’ll consider this in detail below.

Objective Lens Size

The front lenses of binoculars are called objective lenses. The job of these lenses is to take in light from the surrounding area and direct the light and the image to your eye. The larger the objective diameter, the more light the binoculars will be able to let in, and the more light they let in, the brighter and clearer the view you see will be. Binoculars typically come in common objective lens diameters such as 21mm, 25mm, 32mm, 42mm, 50mm and 56mm. You can tell the size of the objective lens of binoculars by reading the second number provided in their name. For example the Tasco OffShore 10x42 Binoculars have 42mm lenses and the Olympus 8x21 RC II WP Binoculars have 21mm lenses. Although larger lenses have the benefit of producing brighter images as they have better light transmission, they do also add more weight to the binoculars and increase their overall size, so the objective lens size you opt for should depend on the activity you plan on using them for. If you plan on using the binoculars in low light environments such as at dawn and dusk, then large lenses will produce better images, however if you plan on carrying the binoculars on a long hike then smaller lenses will allow them to be more lightweight. We’ll consider the best lens diameter for different activities below.


Binoculars are generally considered to be described as compact, mid-size, full-size or giant. The size of a binocular is governed by the size of its front, objective lenses. Compact binoculars have lenses that are around 20mm to 25mm in diameter. Mid size binoculars have 30mm to 32mm lenses. Full sized binoculars have lenses between 40mm and 44mm. Giant binoculars have lenses that are anything over 50mm. We use these terms to group certain types of binoculars so that it’s easy to explain what sized binoculars will work best for different activities. For example, compact binoculars are usually good for travel or hiking, mid sized binoculars are good for tramping and animal watching when you need to keep weight to a minimum. Full size binoculars are commonly used for bird watching and hunting. Giant binoculars are used for hunting in very low light or sometimes star gazing. Many of our buying guides suggest a certain size of binocular for a specific activity, however it’s not vital that you know whether the binoculars you choose are a certain size, it’s more important to focus on their magnification and objective lens instead.

Prism Type

All sports optics are built with lenses and prisms. The job of prisms is to reflect light so that it reaches your eyes. Without the prism, the objects seen through the lens will be upside down. Binoculars can either have a porro prism design or a roof prism design.

  • Porro Prism – Porro prisms were first invented in the 1960’s and offered an easy to make, cheap binocular option for casual use. Porro prism binoculars have an angular design where the two barrels start off together near the eye and then move further apart nearer the front, objective lenses. This traditional design is still available today however as they’re quite bulky and heavy they’re being favoured less by users. They are however cheaper to make so are still appealing to some people.
  • Roof Prism – Roof prism binoculars offer a more modern design where both barrels are straight and run next to each other. They are more compact and lighter weight than Porro prisms. The design also means that they’re more comfortable to hold, easier to make waterproof and can allow for higher magnifications. Users are increasingly drawn to roof binoculars to keep weight down and make for a more enjoyable experience. Unfortunately roof binoculars are harder to make so they are more costly but well worth the money.

Lens Coatings

In order to ensure that light transmission occurs as well as possible, almost all binoculars (except for toys) have at least some coatings applied to their lenses. These coatings are especially formulated to direct as much light through the lenses and prisms of a binocular as possible so that it reaches your eye. The better formulated and the more coatings that are applied, the better quality optics you’ll get. Binocular lens coatings are generally described in the following terms:

  • Coated – Only one coating is applied to the lenses of the binoculars. Minimal coatings aren’t ideal and less light will get to the eye. Low end and cheap scope options will have this option.
  • Fully Coated – This means that all of the outside glass of the binoculars has a coating on it. This isn’t ideal but some of the lower end binoculars are made like this.

  • Multicoated – At least one external lens of your scope has more than one layer of coatings on it, but not all of them have more than one. With sports optics, the more good quality coatings on the lenses the better so this option is better than coated and fully coated but not the best.

  • Fully Multicoated – All external lens surfaces of your binos have several layers of coatings on them, significantly increasing light transmission.

Almost all mid to high end binoculars will have fully multicoated lenses and if you can afford it then they’re well worth the extra dollars. 

Exit Pupil

In short, the exit pupil measurement gives you an idea of how good a binocular is at directing light to your eye. Measured in mm, the exit pupil of binoculars tells you the diameter of the beam of light leaving the eyepiece of your scope and entering your eye. A large exit pupil is an advantage when using your binoculars in low light conditions and at night because, up until a certain point, the larger the exit pupil, the brighter the image you will see. Choosing binoculars based on their exit pupil isn’t necessary and we think that it’s more important to choose the right sized objective lens for your needs. This should, in turn mean that the exit pupil of the binoculars is the best it can be for your needs too.

Field of View

The field of view of a binocular refers to the amount of the landscape/image that’s in front of you that you can see at one time when looking through them and without having to pan the landscape. Field of view is measured in feet or meters at either 1000 yards or 1000m. For example, one binocular may offer you a field of view of 90m and the other may produce a field of view of 100m. In this case, the ones with 100m will allow you to see more of the ocean at one time than the ones with the 90mm field of view. Field of view is governed by the magnification of a binocular with higher magnifications resulting in a smaller field of view. When it comes to comparing the field of view of binoculars, it’s important to consider whether you want to view your subject in great detail, or would prefer to be able to keep track of it if it is moving quickly; after all, there’s no point being able to see the fine detail on a bird’s feather if you can’t find the bird in the first place!

Eye Relief

The term eye relief refers to the distance that you can hold the binoculars away from your face whilst still seeing clearly through them without any dark shadows appearing in your field of vision and distorting the image you see. Eye relief is measured in mm, with the higher the number meaning the further you can hold the binoculars away from your face. The eye relief of binoculars is particularly important if you’re an eyeglass wearer as you’ll need to hold the binoculars further from your eyes. If you wear glasses then look for binoculars with an eye relief as high as possible.

Relative Brightness

Another factor to consider when comparing binoculars it their relative brightness. The larger the relative brightness number given to a binocular, the brighter the image they produce will be. If you’re choosing between two binoculars with similar magnifications then choosing the one with a higher relative brightness will mean they have brighter images. 

Twilight Factor

Twilight Factor is a number used to compare how well binoculars perform in low light. The larger the twilight factor, the more detail you can see in low light conditions such as dawn and dusk. The magnification of the binoculars has the biggest effect on the twilight number, with higher powered binoculars being able to provide you with much greater detail and image identification. The only time that this may not be true is if you’re comparing binoculars that differs significantly in their optical quality or the lens coatings they use. In this situation, the higher quality binoculars will likely have a better twilight factor.


When it comes to focusing binoculars, everyone has different eyes and will need to focus their binoculars accordingly. In addition, most people have one eye that is slightly stronger than the other, so being able to make slight adjustments to the focus of each eyepiece of a binocular independently makes for a much clearer and more comfortable viewing experience. This is why a diopter adjustment is such a great feature on binoculars and something we always advise customers to look out for. Located on the eyepiece of one binocular barrel, the diopter ring allows you to make specific adjustments to just one eye after you’ve completed the main focusing of the binoculars. This fine tuning means that both eyes are catered for. We always suggest looking for binoculars with a diopter adjustment, and luckily most quality binoculars include one.


More often than not, binoculars are used outdoors where they get exposed to different weather conditions and a range of temperatures. Due to this, wherever possible, we suggest that you opt for binoculars that are as weatherproof as possible. Waterproof binoculars are important even if you have no intention at all of using them near water, or in the rain. This is because variations in temperature can cause fogging deep inside binoculars that are not waterproof, resulting in condensation building up inside them and leaving them unusable. Waterproof binoculars are usually more expensive than non water proof models but they are always worth the extra money.


To make binoculars waterproof, they’re filled with nitrogen gas and then sealed with special o-rings. This keeps any moisture out of the binoculars allowing them to maintain their waterproofness.

Choosing Binoculars Depending On Your Needs

Now that you know what features to consider when looking for binoculars it’s time to consider which ones will be best for different activities. Binoculars can be used for a whole range of activities and basic, all-around binoculars can serve many purposes. However, if you have a specific activity in mind that you’re shopping for, it is preferable to choose ones designed with that specific use in mind as they’ll provide much better results.

Bird Watching Binoculars

8x42 and 10x42 are great bird watching binoculars. It’s also important to opt for waterproof binoculars that are as light weight as possible in their class. You can read our handy buying guide for bird watching binoculars here.

Hunting Binoculars

Hunting binoculars should be waterproof and durable so they can withstand the rigours of the hunt. Keep them as compact as possible whilst opting for those that will produce the brightest images. 42mm lenses or sometimes 50mm lenses are great for use in low light. Check our our guide to buying hunting binoculars here or view all of our hunting binoculars here

Hiking and Travel Binoculars

Getting a closer view of animals, landscapes and rivers whilst out hiking is made much easier with some compact or mid sized binoculars. In addition, travel binoculars will make a trip of a lifetime even more memorable as they’ll let you get up close and personal with sights that you just can’t see with your naked eye. Both activities will be much more enjoyable with 8x or 10x binoculars with lightweight lenses from 20-32mm in diameter. Check out our travel binoculars buying guide here or view all binoculars for travel here. 

Marine Binoculars

Whether you love fishing, or need help with navigating whilst out at sea, marine binoculars will give you the eyes you need to see more clearly. For marine activities it’s vital to choose waterproof binoculars and choosing ones that float is also a great idea. Highly magnified images are susceptible to image shake, so opting for low magnification binoculars such as 7x50’s is a great choice for marine activities. Check out our detailed buying guide for marine activities here and view all marine binoculars here

Astronomy Binoculars

As a first port of call, a telescope will always be the best option for astronomy, however binoculars can be a great option for occasional star gazing. Due to extremely low light conditions after dark, opting for binoculars with as large a lens as possible is vital. There aren’t many on the market, but 56mm lenses are a great option. In addition, try and stretch your budget a little and choose the very best quality lenses you can afford for brighter, clearer images. Our handy buying guide for astronomy binoculars will give you more tips and you can view all astronomy binoculars here

Safari Binoculars

When it comes to binoculars for safari, there are a few factors to consider. Often safari animals can only be seen at dawn and dusk when light levels are low, so opting for binoculars with the very best quality lenses and lens coatings and with decent sized lenses is really important. Unfortunately, weight is often a big factor when packing for a safari, so we usually suggest 8x42 or 8x32 binoculars as a great compromise between brightness and compactness. Check out our Safari binocular guide here.

FAQ's about Buying Binoculars

Are binoculars worth it for hunting

In short, Yes! It’s vital to take binoculars hunting with you. Hunting binoculars allows you to scan the landscape for the animals that you’re trying to hunt so that you can pin point your target before even considering trying to aim at it with your rifle and riflescope. Once you’ve located some animals of interest with your binoculars, we’d then advise using a hunting spotting scope to get a closer look at them and to confirm that they animals are the right age and species.

How do binoculars work step by step

Binoculars have front and rear lenses. The job of binoculars is to take in light through their front lenses and to use internal prisms and lens coatings to reflect the light within the binoculars and direct it to your eyes through the rear lenses. In the middle of this process, special prisms magnify the image by a certain number of times so that you can see bright, clear and magnified images through them.

How do you fix out of alignment binoculars

If you’re binoculars don’t appear to be working properly then the best thing to do is to contact the retailer that you purchased them from as they may still be under warranty so you’ll be able to get them checked and potentially repaired or replaced for free. If they’re not under warranty then we’d suggest trying to find a repair agent in your area. We’d never advise trying to fix your binoculars yourself as you may cause more harm than good.

Should I get 8 or 10 binoculars

Binoculars come in a range of magnifications to suit your requirements. The magnification of a binocular tells you how many times they will magnify the image you see compared to that of just using your eyes. So 8x binoculars will show things to be 8x closer than you would see with your eyes, and 10x will be 10x closer. In general, both 8x and 10x binoculars are great for hunting or bird watching and it all comes down to how far away you want to see.

What binoculars do I need for hunting

When you’re looking for binoculars for hunting we always suggest those with either an 8x or 10x magnification with around 42mm lenses. Ensure that they’re waterproof and have a durable construction to help protect them from damage in the bush. Make sure that you spend as much as you possibly can as with optics you always get what you pay for.

What to look for when buying binoculars for hunting

When you’re looking for binoculars for hunting it’s key that you make sure to research all of their key features and compare the specifications offered by one binocular compared to another. Binoculars that appear to have very similar specifications, for example both are 10x42’s, may differ hugely in their construction quality, lens quality and more. Ensure that you opt for binoculars that are as high a quality as you can, are waterproof and if possible have high definition lenses.

Explore Our Range Of Binoculars

When it comes to choosing binoculars there’s a wide range of factors that you need to consider to ensure that you buy the very best suited and value for money binoculars you can. We hope that our guide has helped to explain how some of these factors will effect the performance of binoculars and which binoculars will be best suited to hunting, bird watching, travel, marine and more. If you need any help at all with choosing your next binoculars then we’ll be happy to help. Our binocular range is extensive and has something for all activities and budgets. Browse our range now.

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