Gadget Bag: Compact Binoculars

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Binoculars are often overlooked, yet very useful tools for outdoor photographers, and not just for wildlife specialists. For the latter, of course, it’s a lot easier to pick up a pocketable 10-ounce pair of binoculars to scan for subjects than to pull out a two-plus-pound DSLR with a seven-pound 500mm supertelephoto lens. (Of course, if you do scan with your camera, you can just push the button to record an image when you find something interesting.) The binocs provide a sense of depth, due to their two-eye viewing, as well as a generally brighter image that makes it easier to spot near-hidden critters. But the binoculars also give the landscape shooter a different way of seeing scenes than the usual unaided-eye view—the narrow field of view tends to focus your attention on smaller segments of the landscape, as well as letting you see details you’d miss with the eye alone. You’ll discover different pictures with binoculars than you would with your naked eye.

Binoculars come in a wide range of sizes and powers, but the 10×25 is a good choice for the outdoor shooter, as it’s truly compact, yet provides ample magnification and usable brightness. The first number in a binocular’s designation is its magnification; the number indicates how much closer a subject will appear than if viewed with the naked eye. In the case of our 10×25, that’s 10 times closer, or 10 times larger, if you prefer to look at it that way.

Celestron Nature DX 10×25

The second number is the diameter of the front lens (the objective), in millimeters. Our 10×25 binoculars provide 10X magnification and have front elements that measure 25mm in diameter. All other things being equal, the size of the front element determines how much light your eyes receive when viewing with the binocs: the larger the objective, the brighter the image. Obviously, a brighter image is better, especially in dimmer light. But large-diameter objectives make for larger binoculars, and when binocs get too big, you tend not to carry them on photo outings. We think 10×25 is a good balance of portability, magnification and brightness (10X, by the way, is about the highest magnification that can be readily handheld).

Binocular specs can list relative brightness in a number of ways, but you can quickly calculate it yourself from the unit’s designation. First is exit pupil diameter. If you divide the diameter of the objective (front lens) by the magnification, the result is the diameter of the beam exiting the eyepiece, one measure of the unit’s brightness. In the case of our 10×25 example, 25/10 = 2.5. In bright light, the eye’s pupils contract to 2.5-3mm, so a unit with an exit pupil of 2.5-3mm will produce an image that looks fine. In dimmer light, the eye’s pupils can dilate to 7mm or more, in which case the image of a binocular with an exit pupil of 2.5 will look dimmer than one with a larger exit pupil. But the 2.5mm exit pupil of our suggested 10×25 unit should work well throughout the shooting day.

Swarovski Pocket Traveler 10×25

Another measure of relative brightness is, well, relative brightness. This is determined by squaring the exit pupil. In the case of our 10x25s, 2.5 x 2.5 = a relative brightness of 6.25. Yet another measure is twilight factor, determined by multiplying the magnification by the objective diameter, then taking the square root of the result. For our 10×25 example, 10 x 25 = 250; the square root of 250 (and thus the twilight factor of our unit) is 15.8. Note that all of these brightness measures are just guides. A really good binocular with great optics and coatings will provide a brighter image than a cheap pair with lesser optics and coatings.

Field of view is the width of the area shown by the binoculars at a given distance. Usually, this is given in feet at 1,000 yards or in meters at 1,000 meters. Wider fields make it easier to find subjects when you bring the binocular up to your eye, but wide-field units also generally cost more than normal-field ones.

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Zeiss Victory Compact 10×25 T*

Another consideration for wildlife shooters, but not so much for landscape specialists, is minimum focusing distance. If you’re going to be looking for little birds perched in relatively nearby trees, be sure to get binoculars that can focus close enough. Speaking of focusing, some binoculars have a focusing unit on each eyepiece, some on just one. With the former, adjust each tube for its eye. With the latter, use the central-focusing knob to adjust the nonadjustable tube until it’s sharp, then use the focusing unit on the other tube’s eyepiece, if necessary, to make that eye’s image sharp, as well.

All of the binoculars featured here are roof-prism models, meaning the prisms are configured so the front lenses are basically aligned with the eyepieces. This makes for a more compact unit. There are also porro-prism designs, in which the front lenses are offset outward from the eyepieces. This provides better “3-D” depth, but results in bulkier units.

If you work in rain, fog or mist, you should opt for waterproof/fogproof binoculars. They have all the moisture removed using nitrogen, with O-rings to seal against the elements. Otherwise, treat your binoculars like your camera in terms of exposure to the elements. Rubberized armor coating protects against impacts, but doesn’t necessary imply waterproofing.

Like cameras and lenses, better binocs tend to cost more, but provide better performance and longer life. BaK-4 barium crown glass produces brighter, sharper images than BK-7 borosilicate glass.

Pentax DCF SW 10×25

A Sampling Of 10×25 Binoculars
A number of companies offer 10×25 compact binoculars; here are some with the kind of image quality OP readers are likely to appreciate. All prices are estimated street prices.

Low-priced, but full-featured, the Celestron Nature DX 10×25 ($99) is waterproof and nitrogen-purged to eliminate fogging, and features a polycarbonate frame. Field of view at 1,000 yards is 315 feet; minimum focusing distance is 6.5 feet. Dimensions are 4.3×4.5×1.6 inches; weight is 12.1 ounces. www.celestron.com

Kenko’s 10x25DH ($229) is a waterproof model with a large focusing knob for easy use. Field of view is 87.3 meters at 1,000 meters; minimum focusing distance is 6.6 feet. Dimensions are 4.3×4.2×1.5 inches; weight is 13.8 ounces. www.thkphoto.com

Leica‘s Ultravid 10×25 BR ($749) features a rubberized exterior; there’s also a BL model with a leather exterior. Nitrogen-filled to prevent internal fogging, the binoculars are waterproof to depths of 16.5 feet, have a field of view of 270 feet at 1,000 yards and can focus down to 10.5 feet. Dimensions are 4.4×4.4×1.5 inches; weight is 9.0 ounces. www.leica-camera.com

Featuring a rugged ABS body with waterproof rubber coating, the Minox BD 10×25 BR ($199) has a field of view of 264 feet at 1,000 yards and can focus down to 9.8 feet. Dimensions are 4.4×2.6×1.7 inches; weight is 10.2 ounces. www.minox.com

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A familiar name in photography, Nikon offers a line of binoculars. The Premier LXL 10×25 ($469) is nitrogen-filled and waterproof, and features Nikon’s Eco-Glass optical system. Field of view is 283 feet at 1,000 yards, and minimum focusing distance is 10.4 feet. Dimensions are 4.4×4.3 inches; weight is 10.5 ounces. www.nikonusa.com

The Olympus Magellan 10×25 WP ($149) is a nitrogen-filled, waterproof, fogproof model with a field of view of 285 feet at 1,000 yards and a minimum focusing distance of 9.9 feet. Dimensions are 4.4×4.5×1.7 inches; weight is 12.2 ounces. www.getolympus.com

The Pentax DCF SW 10×25 ($115) is waterproof to a depth of 3 feet, nitrogen-filled to eliminate fogging and rubber-armored. Field of view at 1,000 yards is 261 feet and minimum focusing distance is 9.8 feet. Dimensions are 4.3×4.1×1.6 inches; weight is 10.6 ounces. www.pentaximaging.com

Swarovski’s Pocket Traveler 10×25 ($829) is waterproof and rugged, with a field of view of 285 feet at 1,000 yards, a minimum focusing distance of 16 feet and individually adjustable eyecups. Dimensions are 4.6×2.3×1.5 inches (folds to 2.2 inches wide); weight is 8.1 ounces. www.swarovskioptik.us

The Zeiss Victory Compact 10×25 T* ($629) nitrogen-filled binoculars are fog- and waterproof, have a field of view of 285 feet at 1,000 yards and focus down to 13.1 feet. Dimensions are 4.3×3.8 inches; weight is 8.8 ounces. www.zeiss.com

Vixen‘s new roof-prism Foresta HR binoculars are available in several sizes. We like the 10×32, which is slightly larger than the 10×25 models that we’ve spotlighted in the rest of this article. As Vixen’s top-of-the-line roof-prism line, the Foresta HR binocs feature the company’s reflection-enhanced coating on the prism to render a crisp image in a variety of conditions. Like all of the models in the Foresta HR line, the 10×32 model is waterproof, and it has the “open-hinge design,” which makes it easy to hold and focus with just one hand. www.vixenoptics.com