Waterproof Binoculars

Story and photos by Tim Farmer

This review originally appeared in Canoe & Kayak magazine in August, 2005.



We had just put in on the rocky Shenandoah when my paddling buddy Doug said he’d heard a splash, like something had fallen from my kayak. Everything appeared to be in order after a quick self-check, but a second look revealed that something was missing: my new binoculars! Evidently they had tumbled from the rear hatch cover of my kayak, where I’d absentmindedly left them after stowing my gear. We began to systematically search the area, drifting across the waist-deep water for what seemed like forever but was probably more like 10 minutes.
The binoculars were on the bottom, but a floating strap with an embroidered logo caught my eye and saved the day. I retrieved them and still use those binoculars today, but one thing I learned from that experience is that you get what you pay for in a good pair of binoculars. A lesser pair would have been ruined.


ALL ABOUT WATERPROOF BINOCULARS


Bushnell, Leica, Swarovski, Swift, Vortex, Olympus, Nikon



The lens
A binocular lens is a little like a telephoto lens for a camera. Each is made up of a series of glass surfaces arranged to capture and transmit light. Manufacturers constantly strive to improve materials and production techniques in search of optical perfection. As new developments in binocular technology come along, they eventually filter through the market. The result is that features once seen only in premium, high-end binoculars are today available to consumers in binoculars that cost a lot less.
“That’s great for consumers,” says Adam Vrotsos, marketing manager for Eagle Optics, one of the largest retailers. “Our job is to help you find the one that fits you.”
Deciding which pair of binoculars is right for you is a very personal matter, he adds. For paddlers, of course, nothing but waterproof binoculars will do. Look for nitrogen-filled binoculars to ensure fogproof performance. (All of the binoculars here are nitrogen-filled.)


The price
Since it’s probably going to come down to how much you have to spend, price is a good place to start comparing binoculars. Decide how much you can afford, Vrotsos suggests, and then look for binoculars with the features you want in your price range. The price of a pair of binoculars generally reflects the quality of the components and the level of precision in the manufacturing process. If you want the best optics and the best construction, expect to pay top dollar. If you want to save money, expect to sacrifice a measure of optical precision or construction quality.
For most people, the right pair of binoculars will probably fall somewhere in the middle. Beyond that, the choice really comes down to what feels comfortable in your hands and is most compatible with your situation. Eyeglass wearers, for example, will want binoculars that offer longer eye relief, the measure of the distance from the eyepiece to the point where the entire image is visible. The choice of a pair of binoculars is so personal that, if you can’t select a model in person, be sure to buy from a knowledgeable retailer with a generous return policy so that you can return a pair if it just doesn’t seem right for you.


The prism
Binoculars come in two basic design styles: roof prism and porro prism. When light passes through a lens, the image becomes inverted; binoculars have prisms to correct this. Porro prisms are distinct because the eyepiece (the ocular lens) is offset from the front (objective) lens. In roof-prism binoculars, the ocular and objective lenses are in a straight line so the design is sleeker and more compact. However, the roof-prism design requires stricter manufacturing tolerances and is therefore more expensive to produce with precision. Two common types of glass are used in prisms: BaK-4 glass is formulated to reduce distortion, resulting in a better image but a higher price tag; BK-7 prisms are less expensive but can darken the edges of the image. All the binoculars selected for this review feature roof prisms and BaK-4 or better prisms.


The numbers
Generally, binoculars are listed according to their magnification and the diameter of the front (objective) lens, e.g., 8×20 or 9×25. The first number refers to the power of magnification; a higher number means greater magnification. An object appears 8 times closer with an 8x binocular than with the naked eye. And while it’s tempting to go for greater power, higher magnification makes it harder to hold the binoculars steady, and magnification above 10x generally requires a tripod. Greater magnification also reduces light transmission and makes it harder to follow a moving object because it narrows the field of view.
The second number is the diameter of the front (objective) lens, listed in millimeters. A higher number here represents a wider-diameter front lens, increasing the binoculars’ ability to gather light but also adding to the weight (and price if it uses high-quality glass).
Divide the objective-lens diameter (the second number) by the magnification power (the first number) and you arrive at what’s called the “exit pupil.” This is the diameter of the image that hits the eyepiece (the ocular lens), and it is one measure of the amount of light that reaches your eye. A larger exit pupil is critical for twilight viewing but less important for daylight use. Ideally, the exit pupil should be equal to or greater than the diameter of your eye’s pupil while you are using the binoculars. It’s no accident that many popular binocular configurations produce a 5-millimeter exit pupil, such as 7×35 and 8×40. That’s roughly the size of the human eye’s pupil at maximum dilation. In normal light, the eye’s pupil constricts to about 2.5 or 3 millimeters, while at twilight it dilates to 5 millimeters or more. A larger exit pupil also helps to keep the image centered in the eye’s pupil if the binocular is moving a bit, such as when you are bobbing in a boat.
The exit pupil is a physical measure, and doesn’t take into account factors such as the quality of the components or lens coatings that increase contrast, color accuracy, and image clarity. “Fully multicoated optics” means that multiple coatings are applied to all optical surfaces, while “coated,” “fully coated,” and “multicoated” designate lesser levels of optical coatings. Phase-correction coatings are designed to provide the best color and light transmission. Lens coatings vary by manufacturer.


Which binoculars for you?
First, decide how much you want to spend, because most manufacturers offer a range of price levels. Then think about magnification, size, and weight. Consider how you will use them. Will you take them along on other activities in addition to paddling? Will you use them backpacking, where size and weight are primary concerns and other factors are secondary? Or are you a birder who demands the finest optical resolution? Any of these binoculars would be appropriate for paddlers, but there are others worth considering. Use this as a starting point because in the end it’s a matter of your lifestyle and your budget.




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Buyer's Guide