how to buy binoculars

Binoculars are essentially 2 small telescopes placed side-by-side, each consisting of a pair of lenses to bring distant objects closer and a pair of prisms in each chamber to orient the image right-side-up.
Most binoculars have glass lenses, which generally provide better image quality, but often cost more than plastic lenses.
Most binoculars have their main lenses spaced wider than the eyepieces, thanks to the Porro prisms they use.

Many binoculars today utilize prisms which bend the light as it enters the objective lens and helps to magnify the image as it passes through the frame.
Binoculars are often specified by a set of numbers such as 7×35 or 8×40, the first number indicates the strength of magnification (how many times closer the subject is to you, 5 times closer, 7 times closer, 10 times closer) and the second number is the size of the objective lens measured in millimeters going across the lens.
When considering zoom binoculars remember that a larger objective lens would fair better giving you the greatest amount of light gathering, however they will be bigger and heavier also.
So if you are looking at a pair of binoculars that have 7x magnification, then you might want to consider a lens size of 35mm or a pair of binoculars listed as 7×35.
For example, a binocular that is listed as 10-22x50mm means the zoom portion is capable of viewing at 10x power minimum and can be adjusted up to 22x power and the 50mm would be the objective lens size ( the larger lenses at the opposite end of the binocular ).
So if you intend on using the binoculars during low light conditions or at night choose a pair with a similar value exit pupil.
The exact size can be measured by dividing the objective lens by the magnification of the binoculars.
Exit Pupil stands for the measurement of the circle of light that appears when you look through the binoculars holding them at a short distance away from your eyes.
While looking through the binoculars at a stationary target about 30-50 feet away, close your right eye and focus using the center wheel until the image is clear for your left eye.
In roof prism binoculars the prisms overlap closely, allowing the objective lenses to line up directly with the eyepiece.
If you hold binoculars away from your eyes and up to the light, you will see a bright circle in the center of the eyepiece.
Phase coated prisms take it one step further, the coating process enhances the resolution and contrast of images coming through the binocular and are generally applied only on more expensive binoculars.
Do identical exit pupil size numbers produce identical brightness levels? Manufacturers of high-end binoculars say no, asserting that a variety of refinements—prism type, lens elements, component quality and optical coatings—all affect relative brightness.
If you anticipate regularly using binoculars in low-light situations—at dawn, dusk, within dense tree cover or while observing the night sky—seek out models with a high exit pupil number, preferably 4mm or higher.
Exit pupil size (measured in millimeters) is calculated by dividing the diameter of the objective lenses by the magnification number.
Example: For 7 x 35 binoculars, 35 divided by 7 equals an exit pupil diameter of 5mm.
If you have 2 binoculars with exactly the same specifications except for objective lens diameter, those with the larger diameter objective lenses will capture more light.
The wider the diameter of the exit pupil, the more light that can pass through, resulting in brighter, easier-to-see images when lighting is poor.
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Binoculars can be used for a host of outdoor and indoor activities, from bird watching to football games, to concerts.
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Individual Eyepiece Focus Binoculars – An individual eyepiece focus binocular requires you to focus each eyepiece when looking at an object, but once focused for your eyes, objects from 40 yards away to infinity are always in focus and require no additional focusing.
We do NOT recommend to use binoculars with magnification over 10x without a tripod – if you go with too much magnification in a hand-held binocular, your image will be very shaky! Also, many people ask – How far can you see with a binocular? – we always answer – You can see as far your eyes can see, but the objects will seem to be closer – magnified by the power of your binoculars.
As with exit pupil and relative brightness, twilight factor should not be taken too literally, since it treats all binoculars, regardless of lens coatings and optical quality as if they are the same.
No Focus, or Focus-Free Binoculars – This is an economy version of an individual eyepiece focus binocular, but the eyepieces are locked and set at the factory and cannot be adjusted.
As with exit pupil, relative brightness should not be taken too literally, since it treats all binoculars, regardless of lens coatings and optical quality as if they are the same.
Zoom Binoculars – A zoom binocular allows the user to increase the magnification in order to focus in on the details.
Compact binoculars with a wide angle are great for concert and theater viewing using a binocular.
Exit pupil should not be taken too literally, since it treats all binoculars, regardless of lens coatings and optical quality as if they are the same.
The larger the objective lens, the more light that enters the binocular, and the brighter the image.
Choosing the right binocular for your specific application can be a challenge and this guide is intended to help you understand binoculars better.
They increase the size of the image you are viewing, and they let in more light than your eyes can, making images appear brighter in low light conditions.  Binoculars consist of two optical systems that are connected by a hinge sharing a common focus system.  Using a Binocular An image can be projected simultaneously for both eyes providing a realistic perception of depth.
Of course, a tripod will be needed for the larger binoculars due to the size, weight, and magnification.  Choose a binocular that has 5mm of Exit pupil or more for best viewing pleasure.
Zooming binoculars might have a perfectly acceptable exit pupil diameter under low magnification but one that’s somewhat small under high magnification.
For example, say you’re looking at a ship that’s 1,000 yards away; binoculars with a 330-foot field of view would show you 330 feet of the ship, measured horizontally.
But a 10×25 pair of binoculars has just a 2.5 mm exit pupil diameter, which is smaller than the pupil of the eye most of the time and will be harder to see through clearly.
Unlike an ice pack for a black eye, eye relief for binoculars takes the form of eyecups that block extraneous light and eliminate glare, and also keep the viewer’s eyes a specific distance from the eyepieces.
So a 10×42 pair of binoculars has a 4.2mm exit pupil diameter.
Using 10×42 as an example, the 10x means that the binoculars offer 10x magnification power; in other words, things appear 10 times closer than they do with the naked eye.
I am looking for a pair of binoculars that has great magnification, for viewing on the water, but is pretty lightweight.
Both terms describe the amount of scenery, measured horizontally, that is visible when looking through a particular pair of binoculars.
It’s the same with binoculars; the larger the objective lens, the more light gets through and the brighter and more detailed the image will be.
Imagine standing in the middle of a giant pizza pie; binoculars with a 6.3-degree angle of view would show the viewer a 6.3-degree “slice” of the 360-degree pie, looking outward.
It is always good to have a broad viewing area, so decide how much eye relief is necessary for you and buy the binoculars that otherwise give the widest field of view.
It helped me understand the terms easily and helped me buy a pair of binoculars best suited for my needs.
Rangefinder binoculars contain battery-powered circuitry and a laser that’s used to measure distance from the binoculars to the object that’s in focus.
That’s because the physical appearance and size of a pair of binoculars is determined by the type of prism they use.
Excellent article and guide with simple and rich contents, helps to any buyer who may be completely unknown to binoculars and terms connected to it.
Binoculars are two identical telescopes ganged together so that a person can look through them with both eyes simultaneously, providing a three-dimensional image similar to what would be seen without the use of binoculars.
If you aren’t able to test out a pair of binoculars before buying, the best you can do is research the brand, look for user reviews and ask questions before you buy.
Stabilized binoculars might contain a gyro that requires power to provide stabilization or perhaps a pendulum-type device that provides stabilization without being powered.
Like a zoom lens, zooming binoculars offer variable magnification.
Binoculars with dioptric correction will have an adjustment on one of the eyepieces that is used to compensate for differences between the two eyes.
Finally, when hiking or orienteering, binoculars will be very useful, but it is important to note that optics are very fragile, and so plastic lenses over glass ones, and a rugged case are probably going to be more important than high power, or the ability to use them at night.
The lack of superfluous casing makes them easy to carry, and substantially lighter than traditional binoculars, however the price tag for higher power models tends also to be more substantial than for the traditional type of a similar magnification.
Understanding this will help you to understand the different factors that will affect price and the features that are available – usually these revolve around optical quality, magnification power, and portability – before moving on to look at different price categories and justifications for buying a more expensive pair depending on what they will be used for.
Bird watching binoculars need to be good in all light conditions, from dawn to dusk, and even have limited night vision.
The first is the type of lens and coating that is used; glass lenses, which are coated on each side with multiple layers, will produce a picture at high magnification which is substantially clearer and brighter than that produced by plastic lenses.
Guy Lecky Thompson is a successful freelance writer offering guidance and suggestions for consumers regarding how to choose binoculars, telescopes , night vision and spotting scopes .
Plastic lenses, on the other hand, tend to make the binoculars lighter, but will be substantially more expensive for the same grade of picture quality.
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Orion Resolux 10×50 Waterproof Astronomy Binoculars provide spectacular views of the night sky with a pleasing flat field of view.
Orion Giant View 15×70 Astronomy Binoculars provide bright, high magnification views of starry skies.
Selecting the right pair of binoculars is a matter of picking the best combination of features for your particular needs, including magnification, bulk and weight, brightness, field of view, optical quality, and cost.
Birding enthusiasts will appreciate a slightly larger model with 36-42mm objective lenses as they provide brighter views with more detail visible than smaller binoculars.
For a given magnification, larger objective lenses yield a brighter image in dim light, but also result in a bulkier, heavier pair of binoculars.
In general, porro prisms provide brighter views, but are often bulkier than roof prism binoculars.
And once you’ve purchased your new binoculars, you’ll need to know how to keep them in good condition, and how to adjust (or "calibrate") them for your eyes so you can get the sharpest view possible.
Yet price is a good measure of craftsmanship and materials, and a wise purchase will give you much pleasure and, with care, should last a lifetime.
Binoculars are a must for watching birds, but choosing which model to buy can be bewildering.
Why does the diameter of the exit pupil matter? It doesn’t as long as there is enough ambient light so that the pupils of your eyes are smaller than the exit pupils of your binoculars.
(You will find telescope information on my Photography & Astronomy Page.) Each side of a pair of binoculars has a prime focal length, an objective lens, an ocular (eyepiece), an exit pupil, and so forth.
Divide 25 by 8 and you get 3.1 (25/8=3.1). So the exit pupil of 8×25 compacts is only 3.1mm. A lot less light reaches your eye from compact binoculars than it does from standard size binoculars.
Ideally, human eyes in excellent condition can achieve about a 7mm pupil opening, so a 3.1mm exit pupil from your binoculars can be quite limiting in dim light.
Read more about this under "Exit pupil." Of course, a large front objective makes for larger, and heavier, binoculars.
Close the right eye (or cover the front of the right tube), and focus the left side of the binocular to your left eye using the center focus control, which is concentric with the pivot shaft between the binoculars.
But the 7×50 binoculars in the first example above have 7.1mm exit pupils, as large as young, fully dark-adapted human eyes, so they never limit what you can see, even at night.
Now let’s figure the exit pupil of a pair of compact 8×25 binoculars.
Divide 50 (the diameter of the objective) by 7 (the magnification) and you get approximately 7.1 (50/7=7.1). 7.1mm is the diameter of the exit pupil for 7×50 binoculars.
But when the ambient light gets dim, and the pupils of your eyes adapt by enlarging, the exit pupils of your binoculars may become the limiting factor.
This is very important information, because the larger the diameter of the front objectives, the more light can enter the binoculars and be focused to your eyes.
For field applications a 4mm to 5mm exit pupil is usually satisfactory and 6×30, 7×35, 8×30, or 9×35 binoculars are probably the most useful compromise for hunting.
(Note: the left eyepiece itself does not focus on center focus binoculars.) Next, close your left eye (or cover the front of the left tube), and focus the right eyepiece to your right eye.
Binoculars are commonly described by using a pair of numbers, as in "7×50" or "8×25." The first of these numbers refers to the magnification offered by the binocular.
For instance, Celestron computes the twilight factor of 7×50 binoculars as 18.7, and the twilight factor of 10×50 binoculars as 22.4, even though the former has a 7.1mm exit pupil, and the latter only a 5.0mm exit pupil.
Individual eyepiece focus means that to focus the binoculars to your eyes, you simply focus the left eyepiece to your left eye and the right eyepiece to your right eye.
Important mechanical considerations include the material the lens barrels themselves are made of, the construction of the lens barrels (one or two piece), the way the lenses and prisms are mounted and retained in place (by sticky tape, glue, or threaded retaining rings), the focusing mechanism, and the outside finish of the binoculars.
Higher power binoculars are hard to hold steady without external support and objective lenses of 40mm or larger tend to make for heavy and bulky binoculars that are a burden to carry.
With the 8×25 compacts in the example above, when it gets dim enough for the pupils of your eyes to exceed 3.1mm in diameter, the binoculars are restricting the light available to your eyes.
Specialty astronomy shops, camera stores, and sporting goods stores (the traditional kind that sell guns, fishing tackle, and binoculars, not the kind that sell apparel and shoes) are usually the best sources for both good quality binoculars and good information.
Thus, other things being equal, you can see better in dim light with binoculars that have large front lenses.
A pair of the common 7×35 size binoculars is probably about as good for all-around field use as any.
Roof prism binoculars have straight tubes (the front/objective lens is in line with the rear/ocular lens), and are therefore more compact, an important consideration for the sportsman.
Porro prism binoculars have a single pivot between the two halves of the binocular, and are therefore easy to adjust for the distance between your eyes.
Thus in "7×50," the "50" means that the front lenses of the binoculars are 50mm in diameter, which is large for hand held binoculars.
So whether you want to get a better view of the local football game, or find a big buck across a canyon, a good pair of binoculars is often indispensable.
For example, 7×35 binoculars have a 5mm exit pupil (35/7=5).
Center focus is faster and easier to use than individual eyepiece focus, once you have initially set the binoculars for your eyes.
The exit pupil can be seen by holding the binoculars at arm’s length and looking through the eyepieces.
Roof prisms are essentially in line inside the optical tubes, and make for a more compact set of binoculars.
A good pair of binoculars is one of the handiest accessories for the astronomer, hunter, sportsman, traveler, birdwatcher, and nature lover.
Quality control costs the manufacturer (and you) money, but it is worth it because the result is a better performing pair of binoculars that can last a lifetime.
A product that is well made of high quality components is "good," and it is always worth the extra money over shoddy "popular priced" binoculars.
That includes what the body is made of, whether or not it is water proof, if it’s adjustable to be eyeglass friendly, the armor coatings for protection and comfort, the lens caps for the eyepieces as well as the objective lenses, a case to hold the binoculars and if they can be attached to a tripod.
In this review site, you’ll find side-by-side comparisons and detailed reviews of some of the best all-round use, standard Binoculars, along with a few tips to help you get the pair that will benefit you the most.
Binoculars are commonly used with these and other activities because sometimes, being able to really enjoy nature or spot the game you’re hunting, binoculars can be a great help.
For hunting binoculars, you typically want a little higher magnification, and for star gazing, much more.
Activities like stargazing require binoculars with much higher magnification than ones for bird watching.
This particular site reviews general purpose binoculars that aren’t specialized to any single activity.
For that reason we took in to consideration the size and weight, as well as whether the binoculars come with a neck strap to help ease the burden of carrying them.
It is measured in millimeters, and the larger the objective lens, the more light the binoculars let in and the brighter the image will be.
Magnification: It is the measurement of how much larger an object appears when viewed through a lens; on binoculars, the magnification is given with a number followed by an "x," such as 7x or 12x.
Binoculars contain prisms that flip objects over to the way you would expect to see them down here on Earth, "right-side up." There are two types of prisms, roof and porro, and each type affects the size and shape of the binoculars.
From watching larger animals, like deer and bear, to watching delicate birds or raptors in flight, a pair of binoculars is an important accessory.
Focusing methods: Many binoculars focus with a central knob to adjust both sides at one time; however, some binoculars have a fixed focus, also known as "focus free," so they will not have a focusing knob.
Larger magnifications can also make it harder to hold the binoculars steady enough to focus; use a tripod for anything over 10x.
Different activities often need different types of binoculars with different binocular features, such as magnification, size of the objective lens and field of view.
If you choose to use binoculars in low-light conditions, such as sunrise or sunset, then binocular features such as exit pupil, light transmission and objective lens diameter are important.
Binocular type Description Full-Size or Standard Typically large binoculars with either a 35 mm diameter or larger objective lens.
Zoom A good choice when more power is needed, zoom binoculars allow viewers to enjoy a wide range of magnification choices.
Objective Lens Diameter: This is the second number used to rate binoculars, and refers to the size of the lenses in diameter.
These premium grade 8×42 binoculars are made in Japan using all the top end components and coatings you expect including ED Glass Lens Elements, Fully Multi-Coated Optics, Phase Corrected Bak-4 Roof Prisms with Dielectric Coatings on the reflective prism surface.
Mid-size fog & waterproof binoculars featuring an lightweight alloy open bridge body with ED glass, phase corrected BAK-4 Prisms containing Dielectric Coatings.
High quality optics including extra low dispersion glass, phase correction coatings on Bak-4 roof prisms wrapped in a tough, lightweight, water & fogproof body.
A very lightweight and compact open bridge body that is tough as well as fog and waterproof do a great job of protecting the high quality optics contained inside these Snypex binoculars.
Designed & made in Germany by MINOX in conjunction with Volkswagen Design, these premium quality, hand finished binoculars come with HD glass, phase correction coatings and a full 30 year warranty.
Perfect as astronomical binoculars, the Celestron Skymaster Binoculars (Celestron 15×70) feature high quality BAK-4 prisms and a tripod adapter bringing you excellent performance at a great price.
A fully sealed Magnesium alloy body, with metal twist-up eye-cups protect high quality and fully multi-coated optics that include phase and dielectric coated BaK-4 prisms to offer a performance that easily surpasses their price tag and thus almost all of their direct competition.
Binoculars with a wide field of view are recommended for viewing a broad area.
Choosing binoculars featuring waterproofing is recommended so there is no need to worry about them if there is a sudden shower or spray of water.
High-eyepoint binoculars with eye relief of 15mm or longer are recommended for eyeglass wearers.
15mm or longer eye relief binoculars are recommended for eyeglass wearers.
If the magnifications are identical, the larger the value of real field of view, the wider the field of view.
Generally, the higher the magnification, the narrower the real field of view.
When selecting binoculars, it’s easy to get bogged down with prism type, magnification, field of vision and an assortment of technical specifications.
I was recently in the market for a new pair of binoculars and when I first started shopping around, I was bewildered by the vast number of makes and models available these days.
These factors differ from one model of binoculars to the next and influence what you get out of your binoculars in terms of image quality, viewing conditions, comfort, ease of use, and price.
Since I received my first pair of binoculars as a more than twenty years ago, I lacked experience shopping for the gadgets myself.
Buying binoculars means considering many different options and tradeoffs.  Photo © Daniel H.
We’ll get to the nitty gritty of these trade-offs later, but for now, remember that when it comes to binoculars, to gain something usually means you have to give up something else.
To temper my own confusion, I decided to put together a summary of the information I gathered from various sources (you’ll find a complete list of my sources at the end of this article, each is well worth checking out).