Not everyone is familiar with optics systems. Binoculars are more than just two tubes taped together, and there are many factors that determine their quality and functionality. So, if you’re in search of good binoculars, what should you look for? Hopefully, this article will inform you how to choose binoculars and explain some of the mumbo-jumbo.
It’s a lot to digest, but all very important to consider. We dive further into each of these aspects in some of the specific product review pages found over here.
Magnification is how much larger objects appear to the viewer through the binoculars rather than without the binoculars. The larger the magnification, the further away one can view objects. With that said, magnification isn’t everything. Some people may believe that higher magnification is always better, but there are many factors that determine how appropriate a set of binoculars is for any particular purpose.
Say, for example, a coffee junky wants to go bird-watching one day and decides to get the highest-magnification binoculars money can buy. He then tries them out, only to find he can’t focus on any birds. His hands are not stable enough to focus on objects so far away, so the binoculars are useless to him. He probably should’ve gone for something more around the 7-10x range. Or, perhaps he should’ve found binoculars with a tripod adapter.
Objective Lens Diameter
Objective lens diameter determines how much light can be absorbed by the binoculars. Generally speaking, larger lens diameters lead to brighter images with better contrast. However, objective lens diameter also determines how large the binoculars are going to be, with larger diameters leading to significantly larger optics to haul around. Most standard binoculars have objective lens diameters between 30 and 50mm, with lower sizes being considered compact and larger sizes being used for stargazing. While objective lens diameter plays a role in how bright and heavy your binoculars may be, it is not the only determining factor.
Exit pupil is simply a ratio of objective lens diameter to magnification, so a pair of binoculars rated as 8×40 will have an exit pupil (in millimeters, mm) equal to 40/8, or 5. It is important to note exit pupil determines how appropriate any individual pair of binoculars will be for low light conditions. Larger exit pupils will be more appropriate in lower light conditions as they allow more light to be focused to your eyes. If you’re going hunting during the early morning hours while it’s still relatively dark, you’ll want to have as bright and clear an image of your target as possible. However, do note that smaller exit pupils are great in broad daylight, as your eyes’ pupils shrink to accommodate the excess light that’s available.
Note that “Eye relief” ties in closely to exit pupil, in that eye relief determines how far from the viewing lens your own eye should be. Larger eye reliefs allow for greater distance from the exit pupil and usually more user comfort. In the case of users with poor eyesight, some binoculars come with very large eye reliefs to allow users to view into binoculars through their own glasses. Most common users can focus binoculars to their eyesight using the internal focusing systems however.
Field of View
Often labeled as “feet @ 1,000 yards / meters”, this determines how large a “picture” you see in your binoculars. Usually, wider fields of view have inherently lower magnifications, and narrower fields of view come with higher magnifications. Field of view is often more a matter of personal preference than measure of binocular quality.
Porro Prisms and Roof Prisms
Prisms are what make modern binoculars so neat. The Porro prism, invented by Ignazio Porro, is made up of completely reflective surfaces and suffers minimal (no) light loss through observation, which is perfect for crisp and defined images. However, their design suffers from a naturally frail structure, and they occasionally need to be recalibrated to allow the user to focus properly. Binoculars which implement Roof prisms suffer from slight loss of light through a surface with less-than-ideal reflective abilities, though they compensate with various coating technologies (Phase, Mirror, and Dielectric for example). Because of their unique prism design, binoculars featuring the Roof system tend to be much smaller and reasonably sized. Depending on your intended use of the binoculars, you might prioritize the Porro prism’s crisp images over sleek design. Or, you might prioritize the roof prism’s lighter design for long journeys on foot.
When you read “Fully Multi-Coated” or “Dielectric Coated,” you might think it’s a marketing gimmick (or, at least I did at first). It turns out that these coatings are crucial to optics performance in binoculars. While not all manufacturers mention specifics about coating types, there are several you should be aware of if you’re in the market for a set.
- Anti-reflective coatings ensure the most light possible makes it through the binoculars to your eyes, which in turn ensure brighter, crisper images for your viewing.
- Phase-correcting coatings improve roof prism binoculars’ image contrast considerably, which will make it easier to determine where the tree stump ends and the turkey begins.
- Mirror and Dielectric coatings improve upon how much light makes it through roof prism designs, with the dielectric coatings usually exhibiting superior performance.
Note that there are differences between “coated,” “multi-coated,” “fully multi-coated,” etc. Generally, there is a several-percent difference in transmitted light between the non-coated and fully-multi coated designs. It may not sound like a lot, but trust me and the companies that bother with the technology; it makes a worth-while difference in image quality to go with multi-coated systems.
Binoculars often come with different methods to focus on images. Some come with independent focuses for each eye piece, as well as a central focus knob. Usually, the user focuses the image in the left eye piece and then matches the right eye piece accordingly. Then the central knob can be used to adjust in day-to-day use. Some binoculars, however, come with a single eye piece focus, or may only come with a central focus. These are meant more for convenience, and may or may not offer the best picture quality or the best comfort. Ask yourself, “Am I looking for convenience, or for comfort and the best picture?”
Last, but not least, in our explanation on how to choose binoculars is the general construction of the chassis. Find out if the binoculars are waterproof or water resistant, especially if you plan on using them in fog, rain, or in muddy terrain. Are they shockproof? Look for that quality for binoculars you’ll take hunting or around rocky terrain. A shockproof Porro prism design will usually hold calibration considerably well compared to its counterparts. Are they camo, or will they draw attention? And how heavy or awkwardly shaped are the binoculars? While they are generally pretty light, if you’re taking binoculars on a hike or hunting trip, an extra couple of pounds or a rigid design could become a nuisance and awkward to tote around.
I hope this article helps you determine how to choose binoculars that are right for you. If you’re looking for additional information on different sporting optics, feel free to check out our newest posts at ScopesHQ!