Whether it’s an Indian Ocean passage you’ve got in mind or a quick jaunt across your local estuary, one truth remains irrefutable: Your senses are still the best navigation aids, and the tools that help those helpers serve us best. For hundreds of years, marine binoculars have enhanced sailors’ most important sense–sight–and still they remain one of our most viable tools. Using them, you can examine the local scenery, inspect rigging at the masthead, or locate and identify navigational aids.
Todays marine-binoculars market is saturated with quality instruments in every shape and size, many of which were developed by companies that honed their optics know-how on cameras.
Many modern marine binoculars even allow you to take a bearing or calculate your boats distance from shore. Finally, a relatively new breed of binoculars–one thats image stabilized–is available, and these compensate for the seas unstable conditions.
Breaking Down the Numbers
Sorting through the morass of glass can be intimidating, but once you understand the terminology associated with marine binoculars and determine your own needs, it’s much easier to choose an instrument that suits both the type of sailing you do and your pocketbook. Most of us have heard the term “7×50.” These two numbers refer to the level of magnification or power (7) and the objective-lens diameter (50) of the glasses. When looking through a pair of binoculars with 7x magnification, an object will appear seven times larger than it is. Or, considered another way, an object viewed at 700 feet will appear to be 100 feet away. The objective-lens diameter is the width in millimeters (mm) of the binoculars’ front lenses. Larger objective lenses transmit more light to your eyes and generally deliver a brighter image.
Consider also field of view–the width of the area visible through the binoculars at 1,000 meters or yards. This area is also referred to, in degrees, as the arc of vision. As magnification increases, field of view decreases. Most 7x binoculars have an arc of vision of 7 degrees. At 1,000 yards, each degree represents 52.7 feet. Because we usually see the world through a 180-degree arc of vision, this limited field of view explains why objects are sometimes difficult to locate with binoculars.
Finally, theres a figure for exit pupil. The exit-pupil value describes binoculars performance in low-light conditions. Exit pupil is the width in millimeters of the shaft of light that travels through the pair of binoculars and enters your eye. The exit-pupil value is determined by dividing the objective-lens diameter by the magnification: in our example, 50 divided by 7 equals 7.1 millimeters. The pupil of the human eye will close to about 2 millimeters in harsh sunlight, but it dilates to around 5 millimeters at dusk and even 7 millimeters at night. To be effective in most conditions, the exit pupil of a binocular, which accounts for image brightness, should measure at least 5 millimeters. Anything smaller renders a dark or incomplete image in low light.
Sailors require marine binoculars that display a large field of view for scanning the horizon, minimize glare off sun-speckled water, transmit maximum light in twilight, and do this without being too bulky–a tall order. Aboard a sailboat thats often bobbing, its difficult to hold binoculars steady, and too much magnification is undesirable. The extremely low arc of vision associated with greater magnification can cause eye strain and makes it difficult or nauseating to keep the object in sight as the boat pitches and rolls. For all these reasons, most cruising sailors choose binoculars with no higher than 8x magnification.
Clarity and Light
Having discussed the significance of magnification and lens diameter for binoculars in marine use, let’s examine a few other features available on today’s market. The ability of the lenses to provide a sharp, detailed image is called resolution. While it’s difficult to quantify on paper, it’s easy to judge in practice. Try the following test: Focus your binocs on an object that’s difficult to see with the naked eye, then adjust the lenses until a clear, crisp image appears. Now move the image to the edge of your field of view. Does it blur along the edges of the lens? It shouldn’t. Now test them at dawn or dusk. To calculate an instrument’s twilight factor, or its ability to perform in low light, multiply the magnification by the objective lens diameter and take the square root of the product: 7 times 50 equals 350; the square root of 350 is 18.7. Binoculars used in low-light conditions should have a twilight factor of at least 15.
While low-light conditions separate the merely good binoculars from the excellent, the majority of your sightings will occur during the day. To this end, manufacturers employ lens coatings that enhance their binoculars performance during the harsh midday sun. A good lens coating should both cut down reflection–internally and externally–on sunny days yet also enhance light at twilight. Since the inherent light-loss of an untreated lens is up to 8 percent, and some binoculars use 18 different lenses, the cumulative effect of inferior lens coatings can be dramatic. Beyond their ability to effectively transmit light, quality coatings also protect the lens. A good coating is harder than the glass to which its applied. But dont be fooled by manufacturers claims: “Fully coated” lenses in a pair of 7×50 binocs can deliver low-light images that lack the clarity and brightness of 7x35s constructed using superior coatings and optics. Despite being optical instruments, binoculars will sometimes be treated like winch handles–especially during Where-are-we? drills. The housing should be rugged, waterproof, and rubber-coated.
These days, binoculars are available in a wide variety of makes and models and in nearly every price range. Where should you begin your search? Marine chandlers are your best bet: Their staffs are generally more knowledgeable about optics than the summer help at your local department store, and they’ll likely stock more binocs suitable for marine use than the local hunting outfitter. Camera shops are another viable option. If you already know what you want, you can take advantage of the low prices offered by discount department stores or mail-order or online marine suppliers, whose catalogs offer a wide range of products.
Once you find a place that offers a suitable array, choose several models that feel right ergonomically–they should feel as though they were designed especially for your hand. Make sure theyre solidly constructed, shockproof, spray-proof (if not actually waterproof), and rubber coated to prevent slippage on a wet deck. Take them outside. Looking through a store window wont do. Binocs will magnify imperfections in the window and should be tested under natural-light conditions. Check for blurring at the edge of the optics, and adjust the barrels so the image merges into one perfect circle. If it doesnt, this will cause undue eye strain. Next, turn the focus mechanisms–they should turn smoothly without feeling loose–and note whether theyre individual or center focus. Most binoculars have individual-eye focus. While its easier for manufacturers to waterproof this style, its more difficult for the user, who has to adjust each barrel of the instrument each time the focus is altered. Center-focus binoculars use a central wheel, or lever, that quickly focuses both lenses. Todays center-focus outdoor binoculars are usually waterproof and nitrogen-purged (to further prevent the entry of moisture), and one of the lenses can be adjusted individually to accommodate visual differences in your eyes.
Now focus on an object for several minutes. Do your eyes or arms tire? Do the eyecups put undue pressure on your face? Do flashes of light or glare appear as the binocs are moved from side to side? Any one of these problems is a good reason to move on. Next, focus on vertical and horizontal straight lines–smokestacks, roof lines, building corners. Do they remain straight when magnified? Finally, determine the eye-relief factor, or the maximum distance in millimeters that your pupils may be away from the oculars (the small lenses) without reducing the field of view. This distance generally ranges anywhere from a few millimeters to almost an inch, which explains why the manufacturers of lower-priced binoculars rarely mention it in their literature. For sailors with nearly perfect vision or those who prefer to remove their sunglasses before using binoculars, eye relief is of little consequence; to those who wear prescription glasses or sunglasses and who prefer to leave them on, eye relief is extremely important. For the bespectacled among us, eye relief should not be less than 15 millimeters. All binoculars provide eyecups of either rubber or plastic that roll down, twist out, or snap up, but the degree of efficiency among them varies widely. Eyeglass wearers beware: Even the brightest, sharpest optics may provide dismal tunnel vision if theyre not eyeglass-friendly.
Beyond excellent optics and ergonomics, many contemporary marine binoculars come equipped with a built-in compass and range-finding scale. Both are visible while looking through the instrument: the compass in the lower portion of your field of view (if its mechanical) and the range-finding reticle (a series of horizontal and vertical hashmarks) in the line of sight. The compass is handy for quick bearings on a marker buoy or landmark, while the reticle–during relatively calm conditions–allows you to calculate distances using the known height of an object and a simple formula.
We Kick the Tires
We were surprised at the sheer volume of makes and models available. When the smoke of initial inquiries finally cleared, 17 manufacturers had supplied us with over 35 pairs of binoculars. No list in a field this large is ever completely comprehensive; we included the manufacturers who are most familiar to the sailing community, and probably a few that aren’t (yet!).
Reviewing optics is a subjective exercise, one thats prone to the likes and dislikes of the persons using them as well as to preferences dictated by their hand sizes, face shapes, and gripping styles. Five editors took 35 binoculars out onto Narragansett Bay for evaluation. Although our approach might have delivered wildly diverse results, in fact, our individual assessments were very much in line.
To break the binoculars down into workable subcategories, we first established three price ranges: Lowriders (under $300), Middletown ($300-$600), and Big Dogs (over $600). Take the prices with a grain of salt: Manufacturers suggested retail prices (MSRPs) are often higher than the street price, and allowable markdowns vary greatly from company to company. For instance, the msrp for the Fujinon 7×50 Polaris FMTRC-SX we tested is $1,160. West Marine sells the same model for $630.
Our reviewers rated each instrument according to three subjective criteria: Image (sharpness, brightness, and center-to-edge focus), Feel (ergonomics, weight, ease-of-focus, and diopter adjustment), and Eyeglass-friendliness (the degree of tunnel vision caused by wearing eyeglasses, the quality of the eyecups, and their ease of use). Each reviewer wore either prescription glasses or sunglasses and tested with them both on and off. Based on these criteria and on a consideration of price, the reviewer ranked the models within each price category in terms of how likely he or she was to actually buy them. Above, binoculars within each price group are listed in the order of our editors preferences.
How They Shook Out
Lowriders: To establish a baseline and ensure a fair test, we looked through each instrument at least once before picking up our pencils and looking through the binoculars again. The level of quality in this least-expensive category was amazing; several of us wondered out loud (after the evaluation in this group was over) how the image quality could get any better in the higher-price ranges. It would get better, of course, but not before wed declared the Canon 8×32 binoculars our overall favorite in this category. The popularity of these binoculars began a trend that wed soon recognize: As a group, we preferred roof-prism binoculars (lenses in line; more compact) and center focus over porro-prism (lenses offset; bulkier) and individual-eye focus, even when smaller optics couldnt guarantee the same light-gathering capacity as 7x50s. By the time wed finished with this group, wed also developed a healthy aversion to rubber eyecups. Nearly every pair in this category had them, and rolling them down to accommodate glasses was tedious. On the plus side, rubber eyecups–even rolled down–provide better cushioning for the eye in heavy seas, and many professionals feel they do a better job cutting out peripheral light.
We also preferred light, solidly built binoculars. Its no coincidence that the Canon 8x32s were the lightest in their price category. At 26 ounces, they were a full pound lighter than the Navy One glasses, which weighed in at a beefy 42 ounces and had flared rubber eyecups that wouldnt roll down. The Canons–despite a lower twilight factor than the 7x50s–seemed like theyd still get you into that dark and stormy harbor. Other favorites in the category were traditional porro-prism binoculars by companies youd normally associate with cameras: the Olympus 7×50 EXPS Pathfinder, the Pentax 7×50 PCF V, and the Minolta 7×50 Activa. The scoring among these three was extremely tight, and given their close pricing, any one of them would be a good buy. In the same price range and just out of the top four was the only model that came with a built-in compass and range-finding reticle, the West Marine 7×50 Sea Search.
Middletown: The real dogfight occurred in this midpriced range. In the absence of roof-prism binoculars, the Bushnell and Nikon models we tested reigned: They delivered incredibly crisp images in housings that just felt ergonomically right. The built-in compass in the Nikon was easily viewed and relatively stable. Nikon was edged out, however, by a Cinderella named Bushnell. The optics of its Marine 7x60s were truly stellar, and their consistently high marks in feel and eyeglass-friendliness enabled them to edge out an excellent Nikon model that was lighter and that came with a built-in compass and reticle. While you might not want the nearly 3-pound 7x60s around your neck all day, they delivered the brightest, sharpest image in a group of binoculars that all seemed to have exceptional lenses. The Fujinon 7×50 Mariner WPC-XL and Steiner 7×50 Navigator II binoculars delivered fine optics, but they were bulky, and their internal compasses were difficult to read. At the lower end of the spectrum, the Tasco 7×50 Off Shore 54 binoculars had a feature that was unique to all three categories: Built into one of the lens casings is a clever dial that enables the user to make quick and easy range-finding calculations.
Big Dogs: After the first two difficult rounds of evaluations, and seeing names like Zeiss, Steiner, Fujinon, and Swarovski in the final grouping, we thought that deciding among the final participants would be nothing short of Mission: Impossible. It was hard to imagine that the optics could improve from what wed seen. Wrong on both counts. The level of optics increased, and deciding between them was by far the easiest of any price range. Leading the pack was Swarovski. These roof-prism binoculars combined all the features we liked: crystal-clear, easy-to-use optics (with or without eyeglasses), center focus, and solid, twist-out eyecups. The snap- and twist-out solid eyecups featured on five of the instruments in this category were big hits among the reviewers. They were easy to use and consistently held the most field of view when wearing glasses. Three of the top-rated binoculars in this group (those from Swarovski, Leica, and Bausch & Lomb) were 7x42s, while the fourth was a porro-prism Fujinon 7×50. All were solid instruments that seemed capable of long voyages aboard a boat, where theyd be expected to survive the usual rough-and-tumble use in a salt-sprayed environment. The heavy porro-prism instruments supplied by Zeiss, Steiner, and Fujinon, while optically impressive, seemed awkward to use, and all made use of rubber eyepieces. And while one of the reviewers aptly pointed out that the heavier instruments were built to last a lifetime, I wondered how much time theyd spend on deck. It was easy to picture the slightly smaller, fun-to-use roof-prism instruments being happily passed around while the heavy instruments sat in their cases below.
Given our united preference for the roof-prism configuration, I contacted Steiner, Zeiss, and Fujinon and acquired from each a pair of their roof-prism binoculars. All three center-focus models–the Steiner 8×42 Predator, the Zeiss 8×56 B T* DesignSelection, and the Fujinon 7×42 CD–were optically outstanding and featured the heavy rubber armor and nitrogen-purged lenses that make their porro-prism brothers so desirable to the serious sailor. Zeiss even provides a transferable lifetime guarantee for their binoculars that can be passed from generation to generation in the same family. While the Steiner Predators make use of angled rubber cups that match the contour of the face (and thus block out more light), we still preferred the snap- or twist-out solid cups that were standard issue on most of the other roof-prism binoculars.
Gone are the days when only a few manufacturers made quality optics and buying a pair meant taking out a second mortgage. Each price range we evaluated showcased fine instruments that were easy to use, durable, and made use of high-quality lenses. Our advice is to first establish your budget, then determine the power, weight, and specification ranges that best suit your needs. After that, go out and test as many models as you can get your hands on: It’s the only way to decide what’s right for you, and it’s fun.
Bob “Squints” Muggleston is a CW associate editor.