15x Binocular Review

May 18, 2019
Gun Review: Kimber Mountain Ascent Subalpine
May 18, 2019

15x Binocular Review

In wide-open terrain, the performance offered by high-quality, large binoculars are worth their weight in gold. 

By Eric Martin, WHJ Gear Editor

When I look back on the collection of all the skill sets I have learned, developed and honed over my last quarter century afield in the West, it is easy to identify the techniques and pieces of equipment that have had the greatest impacts on everything from scouting terrain and animals, to putting little white packages in my freezer.  

There is an ever-expanding myriad of clothing, knives, scents, calls, gadgets and doodads that are continually presented as the sure-fire critical component to which success is dependant. Advanced clothing can make time spent afield much more comfortable. Precision ammunition can produce astounding accuracy. Packs made to haul meat could also handle the rigors of an Everest summit. Detailed mapping software can allow for effective scouting of hunt units and terrain hundreds of miles away from the comfort of your recliner. These, and countless other pieces of equipment, no doubt provide benefit to hunters of all likes, but when it comes to hunting the vast open expanses encountered on many Western hunts, the biggest hurdle a hunter must overcome, is simply spotting game. 

Personally, stepping up my glassing game was the single most beneficial component for finding consistent success hunt after hunt. Like most hunters, I carried binoculars and would use them to stop and glass at times throughout a hunt, but I never really focused effort, or equipment, on mastering glassing. I relied on smaller, compact, lower magnification optic styles which produced a quick, wide field of view; stopping to quickly scan an area for easily identifiable (i.e., broadside, in the open) animals. After a few minutes, I’d continue on with my hike, stopping occasionally to repeat the process.

This all changed after spending some time in the hills with friends who literally made their living finding animals. “Glass first, hunt later,” they exclaimed, while sitting behind tripods topped with binoculars much larger than anything I had ever carried on a hunt. Their logic was simple: Spare your body the fatigue of hiking miles of terrain, and stay stealthy by not spooking animals out of the country with unneeded movement in the hunt area. Instead of quickly scanning for openly visible animals, as I had done for so many years, they slowly and methodically picked apart the landscape in segments, using the advantage of increased magnification to search not for entire animals, but for pieces — an ear, a tail flicker, sun glinting off an antler. 

While many may feel the need to pack a spotting scope for such glassing situations, relying on larger 12x, 15x, and even 18x binoculars can kill two birds with one stone, eliminating the need to carry multiple sets of optics. For many, binoculars prove to be more user-friendly; producing less eye fatigue, a more comfortable field of view, greater depth of field, ease of focusing, and a more compact overall size. Target acquisition is also easier with binoculars, especially on moving targets, and unlike spotting scopes, large magnification binoculars can be handheld or used with a tripod. 

Like most people, I have found the process of selecting a standard pair of binoculars to be to be a bit nerve racking, especially when done in the confines of a retail store, or worse, over the internet. There is such a wide range of construction and materials that options, prices and ultimately performance vary wildly. I liken it to trying to test drive cars, but being restricted to slow speeds under uniform residential settings. You only scratch the surface as to what may be under the hood. Even when you’ve done your due diligence on making a selection, issues and disappointment often arise once you put it through its paces in a real word environment. 

Thankfully, selecting larger magnification binoculars is much less stressful; at least once you get past the price tag. With optics, shortfalls in performance such as lack of sharpness, color distortion, darkness and eye strain are intensified as magnification increases. Coupled with the higher costs of construction from larger lens and prism elements, places a great degree of pressure on manufacturers to either make it perfect, or don’t bother making it at all. The result: available large magnification models in the retail setting are at the pinnacle of performance. This is not to say that you can select any model at random and expect it to perform optimally for your specific needs. To do so, one must have some knowledge of construction details, and how they relate to overall function.

Binocular design has shifted towards roof prism construction as all the glass elements and prisms are in a straight line producing a sleek, streamline body design which is easier to pack and hold versus the wide, offset Porro prism designs many of us grew up with. A downside to roof prism design is they are more labor intensive to build, which results in a larger price tag than a Porro design built with identical components. 

One of the biggest drivers of both price and performance is the quality of the glass and prism elements being used. While all glass appears clear, lower quality glass will have tiny imperfections which bend and distort the way light passes through, affecting everything from brightness and correct color representation to sharpness of focus. As white light impacts a lens, the varying wavelengths (colors) will be refracted at different rates producing a rainbow, called dispersion. In larger binoculars, high quality crown (borosilicate BK-7, barium Bak-4), fluoride, ELD (extraordinarily low-dispersion), ED (extra-low-dispersion), or UL (ultra-low-dispersion) glass is most commonly used to minimize dispersion. If a lens fails to refocus all wavelengths back to a single point of convergence, chromatic aberration will occur. This produces fringes of irregular color around the contrasting edge of objects in the field of view.

Roof prism binoculars can be constructed using a variety of prism designs which may or may not be denoted by the manufacturer in specification guides as you do your research. Popular systems are Abbe-Koenig, Amici and Schmid-Petchan. Designs such as Schmidt-Petchan are less costly to produce, and are shorter in overall length, thus shortening the length of the binocular; however, they must be treated with special coatings, ideally dielectric coatings, to maximize light reflectivity off their surfaces for maximum light transmission. Abbe-Koenig systems are longer, harder to manufacture and produce the highest degree of light transmission and are typically seen on the most premium of binoculars. When it comes to materials used, look for models which use barium crown BaK-4 prisms such as Schott BaK-4 versus BK-7. Any easy way to check is to turn the binocular around and look through the objective end from a distance of about a foot. If the view has a perfectly round appearance, they are likely BaK-4; if a squared off image can be seen, they are BK-7.

For hunting situations, performance in low light is paramount as these are the situations when animals are most active. A variety of factors play into low light performance including glass quality, lens coatings, prism types and coatings, and exit pupil. On untreated glass, a percentage of light is reflected off the surface, absorbed as it passes through, and then again reflected off the rear surface. Multiply this by all the lens elements in binocular construction, and the potential for significant light loss is easily evident. Specialized films and chemical coatings reduce light loss due to absorption or reflection, and allow more light to reach your eye. They can also help to correct details such as color rendering and contrast. Coatings can be as minimal as a single layer on one air-to-glass lens surface (Coated), a layer on the front and back of air-to-glass surfaces (Fully Coated), or multiple layers on all glass and prism surfaces (Fully Multi-Coated). These coatings are costly but absolutely worth it if you want optics that won’t fail you in low light. Look for models that are multi-coated, or fully multi-coated. 

The size of the exit pupil at the ocular lens is also a light limiter. Hold binoculars at arm’s length in front of you and the small circle of light visible in the ocular lens is the exit pupil. It is simply a factor of the objective diameter divided by the magnification. A 56mm binocular with 15x magnification equals 56/15, or 3.73mm exit pupil. The human pupil fluctuates between 2mm and 8mm depending on how it dilates in ambient light. Any time the optic exit pupil is smaller than your pupil diameter, light reaching your eye is being reduced. So, all models with the same sized exit pupil produce identical light transmission, right? Not even close. This is where the coatings on the lens elements play a huge role. Even with the same size exit pupils, better glass with better coatings will transmit more light. 

It is also important to not only compare models on their field of view, but also on the edge-to-edge performance of that view. Field of view is simply the viewing range at various distances. It may be specified in linear measurements such as X feet per X yards, or in terms of the angular field of view expressed as degrees to a 360-degree circle. For reference sake, a field of view over 60 degrees is considered a wide field of view. A wide field of view allows you to cover more terrain as well as quickly acquire moving animals.

A common technique with larger optics is to set the view via a tripod, then without moving the optics, methodically look over everything in the field of view, edge-to-edge, rather than pan back and forth across a piece of terrain while focusing your attention to just the center of your field of view. To do this effectively, you must be able to see clear, sharp detail across the entire field of view. This is where poor quality optics with lesser-grade glass will come up short. The edges will start to blur, colors will skew, or the image may distort or stretch. When evaluating a potential purchase, don’t just judge performance by the clarity and color of the center of the viewing area, pay attention to the edges.

In terms of overall construction, any hunting binocular should be waterproof and filled with an inert gas such as nitrogen or argon to prevent internal fogging or fungus development of the lenses. Rubberized outer coatings are common and provide both warmth and grip when wet. Handle models when possible to make sure the size and shape of the body fits well in hand while allowing easy manipulation of the focus adjustment. Focus knob tension should be light enough to allow precise fine adjustment without feeling so loose that you roll in and out of focus on fine adjustments, or so snug that minor adjustments are difficult. Adjustable eye cups are standard with most models to allow for use with the naked eye or with glasses; however, some models feature a series of adjustment stages that allows precise fitting to your vision needs rather than a smooth, continuous in/out setting that can be bumped out of adjustment during use. 

The diameter of the eye cups is also important. I struggle achieving a good fit to my eye if the eye piece is too bulky. Dioptric adjustment, typically a ring on one ocular, allows custom tuning to your specific eye characteristics, but not all models offer the same amount of adjustment range, so if you have a strong prescription, you may need to look into specifications closely. Look at features such as the attachment points for a neck strap, and how easy it is to mount a tripod adapter, or if a model requires a specific style of adapter. Recessed neck strap attachments are less likely to snag on clothing or pack straps, and also are less prone to breaking.

The construction needed to produce a high performing pair of large magnification binoculars results in a noticeably heavy final product. Bear in mind, these styles of binoculars are not intended for simply slinging them around your neck and hitting the hills for a 10-mile hike, or for use in thicker vegetated areas where visibility is limited. They are meant to be utilized from vehicles or key vantage points of the terrain where you can sit for long periods and cover miles of ground with your eyes, not your feet. They are most comfortably carried in a chest harness system or in your pack, and performance is optimized when matched with the stability of a good tripod. 

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