Selecting the perfect pair of binoculars can be a tricky task, given the sheer number of types and styles available, and finding high quality binoculars online depends upon many factors, one of the reasons why many people need the specifications of binoculars explained. For example, an astronomer needs a powerful pair of binoculars to observe distant heavenly bodies, whereas a hunter or ornithologist is best served by a lightweight option that magnifies without losing color or clarity.
Too many people rush out and buy the most powerful, expensive binoculars they can find, without realizing that bigger is not always best. For example, high-magnification binoculars are great for spotting far off birds, but they are too heavy to use without a tripod and lose many of the vivid, beautiful colors that make ornithology such a rewarding pastime.
Choosing the best binoculars involves understanding a little behind the science of optics – you don’t need a degree in physics, but knowing what all of the numbers and specifications mean will prevent you from wasting your money on an unsuitable pair.
Top Compact Binoculars
Binoculars Explained – Magnification and Aperture
A pair of binoculars always carries a set of numbers, such as 15×70 or 10×30, stamped somewhere on the casing, and this is the most important factor determining your ultimate best binocular choice.
The first number is the magnification of the binoculars, simply telling you now much larger an object will appear. For hand-held use, 8x – 12x magnification is enough, because higher magnifications exaggerate any shaking, requiring a tripod for effective use.
The second number is the diameter of the objective lens, measured in millimeters, with a larger lens affording much more clarity, light and detail. Smaller lenses are great for maximum portability, but they can lose a lot of light and color, making them a poor choice for overcast days and low light conditions.
Dividing the second number by the first gives you the exit pupil size, and a larger number is better. For low light conditions, you should look for a pair with an exit pupil size of over 5mm, and for everyday use in broad daylight, you will get away with 4mm. Because of this, and to avoid losing clarity and detail, higher magnifications should be coupled with larger objective lenses, but this means that you will have to carry around an unwieldy tripod or monopod.
Some manufacturers use the ‘Relative Brightness Index,’ by squaring the exit pupil measurement, with an RBI of over 25 suitable for low light conditions, such as dawn and dusk.
Binocular Field of View
The third number is the field of view, given as an angle or as a measurement in feet or meters. If the field of view is given as an angle, multiplying this number by the magnification gives the apparent field of view in degrees. For example, a pair of 10x binoculars, with a field of view of 7o,has an apparent field of view of 70o, with anything over 650 is considered ‘wide view.’
Some manufacturers give the FOV as the width of the scene visible 100 yards away, in feet, such as 252 feet over 1000 yards. Roughly speaking, 1-degree apparent field of view is roughly equivalent to seven yards. To complicate matters further, non-US manufacturers use metric measurements, in visible meters over a 1000-meter range – 7m is roughly equivalent to 1-degree.
The importance of this is largely down to personal preference; a large apparent filed of view is great for looking at landscapes, sporting events, or entire flocks of birds, but it is not as important for looking at individual objects.
Other Factors Influencing the Best Binoculars
Special Coatings – Glass is reflective and light bouncing from the lenses can intensify the darkening effect associated with low exit pupil sizes. In addition, reflective lenses can create flashes of light that can spook animals, undoing all of your hard work in getting into position. If you intend to use your binoculars frequently, specially coated binocular lenses are ideal, but you will pay a little extra for this.
Some of the coatings are:
Coated Binoculars: At least one lens surface has a coating, to reduce glare.
Fully Coated Binoculars: All of the lens surfaces in contact with the air are coated, to reduce glare and improve contrast
Multi-Coated Binoculars: At least one lens surface is coated with multiple layers, reducing glare and increasing clarity, contrast, and color intensity.
Fully Multi-Coated Binoculars: All air-to-glass surfaces are coated with multiple layers, giving the maximum improvements in clarity, contrast and intensity
Phase Coated Binoculars: High quality roof prism binoculars can be coated, giving excellent glare reduction, light intensity, contrasts, and clarity, but they are expensive and unavailable for Porro prisms.
About Binocular Prisms
Porro Prism Binoculars
Porro prisms are the traditional prisms used in binoculars, creating the familiar ‘shoulders’ found on standard binoculars, and they bend the incoming light and send it to the eyepieces. Despite the popularity of other, more portable binoculars, Porro prism binoculars are still a great choice, because they are cheap and extremely durable, especially if you look for a rubberized binocular casing, which ensures that the prisms will not be knocked out of alignment if you drop your binoculars.
Roof Prism Binoculars
Roof prism binoculars incorporate small prisms in the roof of the casing, giving high magnification without sacrificing portability. Roof prisms are perfect for portable binoculars that can fit into a pocket, but the smaller aperture means that they lose some clarity, and roof prisms tend to be a little more delicate than the Porro prism. A high quality, rugged set of roof prism binoculars can a little too expensive for occasional use.
High Quality Binoculars
Other Binocular Specifications
Eyecups and Adjustability – If, like a large proportion of the population, you wear spectacles, try to find a pair of binoculars with roll-down, rubber eyecups. A good pair of binoculars will allow you to fine-tune the eyepieces individually to take into account the fact that eyes generally have a slightly different focus and strength. Many binocular manufacturers use the term ‘Long Eye Relief Binoculars,’ showing that they are suitable for spectacle wearers.
Tripod Mount – For larger, heavier binoculars, make sure that they have a standard tripod mount, allowing you to provide a stable platform for maximum stability.
Nitrogen Filled Binoculars – In cold, wet conditions, condensation inside the case of the binoculars caused fogging on the inside of the lenses, rendering them unusable until you returned home and dried them out for a few hours. High quality binoculars are injected with nitrogen gas, inside a waterproof, hermetically sealed casing, preventing fogging. Of course, the downside of this is that nitrogen binoculars are expensive, but they are perfect for the hardcore hobbyist or professional in damp, temperate climes.
Bird Watching Binoculars vs Astronomical Binoculars
Bird-Watching Binoculars and Hunting Binoculars
Ideally, a pair of binoculars for spotting should be light and portable, with a decent magnification and objective lens, giving a large field of view and maximum color capture. If you intend to use them frequently, roof prisms are a great option, although you may sacrifice clarity and light intensity. For bird watching and hunting, anywhere between 8x and 12x magnification is perfect, unless you intend to carry a tripod.
Most astronomers use a tripod, so portability is not as important, allowing them to really go for the high-mag binoculars and pick up faint objects. For astronomy, high magnification and large objective lens size are usually essential, allowing the amateur astronomer to pick up faint objects.
Generally, astronomers need a large pair of binoculars, such as a 20×80, but the weight can render them unusable, so make sure that the pair that you buy can be mounted on a tripod.
The Voice of Experience – Ask the Experts About Binoculars
If you are still a little unsure about how to find the best binoculars online, ask experience hunters, ornithologists or hunters what type they use. Through trial and error, they will have found the best type for the job, finding the perfect balance between budget, practicality, portability, durability and magnification. Once you find the perfect compromise, buying binoculars online is easy.
Personally, I always carry two types of high quality binoculars for birdwatching: A small, portable pair of roof prism binoculars for catching a fleeting glimpse of birds, and heavier, Porro prism binoculars for maximum clarity and magnification. Hopefully, with a little knowledge and the principles behind binoculars explained, you will be able to find the perfect pair and indulge your passions.
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