| Miscellaneous | Binoculars: A Buyer's Guide The right optics can bring the beauty of the natural world closer. But it is very important to find the optics that are right for you. This guide will help you find binoculars that are just the right fit. Visit our Audubon Shop for information about a variety of optics and accessories.
STYLES
Porro prism binoculars are the traditional style, where the lenses you look through (ocular lenses) are close together, and the larger lenses (objective lenses) are further apart. Thus, the two lenses do not line up. This style is less expensive to manufacture and repair, but is also more prone to damage in the event of a mishap.
Roof prism binoculars are a newer style, with the ocular and objective lenses lined up, tube-like. Roof prisms are expensive, but can often withstand an accident that would damage porro prism binoculars.
MAGNIFICATION
Each pair of binoculars is marked with a set of numbers such as "8 x 42," which refers to the magnification (8) of the binoculars and the diameter of the objective lens (42). The magnification used by most birders is usually between 7 and 10, but don't make the mistake of thinking bigger is better. A smaller magnification usually means you can see a wider area, and it is easier to keep the image steady. With larger magnification, you can see more detail. If you are inexperienced in using binoculars, it is often best to go with a smaller magnification.
BRIGHTNESS
The second number in the formula on binoculars (i.e., the "42" in 8 x 42) refers to the diameter of the objective lens. The higher this number, the more light can enter the binoculars, and, theoretically, the brighter the image should be.
There is another element, however, that affects the brightness of the image, and that is coating on the lenses. Every time light hits a glass surface, such as a lens or prism, it reflects away (and loses) some of the light. Since binoculars have many glass surfaces, this loss can be significant. Lens coatings eliminate much of the light lost by reflecting off uncoated surfaces. "Fully-coated" means that all the glass surfaces are coated. Multiple coatings reduce light loss even more, so "fully multi-coated" is even better.
EYE RELIEF
If you use eyeglasses when you look through binoculars, this may be one of the most important issues you consider. With a short eye relief (under 15 mm), it can feel like staring down a drain pipe, so be sure to select binoculars with over 15 mm of eye relief.
FIELD OF VIEW
This measurement tells you how wide an area you can see through your binoculars. The more you can see, the easier it is to follow a fast flying bird, or catch movement to the side. This is measured either in degrees or in feet per thousand yards. Look for a minimum of 6 degrees, or 300 feet at 1,000 yards.
BINOCULARS THAT ARE RIGHT FOR YOU
The most important feature in choosing binoculars is finding a pair that feel right to you. Pick them up, and hold them, and notice how they feel. If your eyes are close together, do they fold down enough for your eyes?
Focus on the closest object you can. Is this distance going to be close enough for you? For example, if you are going to look at butterflies as well as birds, a close-focus of 15 feet may be much too far away.
Play with the focus knob, and decide if this is a natural movement for you. Is it easy to locate and focus on an item in the distance, or is the focus finicky? Binoculars an an investment that you can enjoy for a lifetime, so be sure you are comfortable with them.
The Audubon Shop, located at Mass Audubon's Drumlin Farm Wildlife Sanctuary in Lincoln, MA, has a fine selection of compact and full-sized binoculars, scopes, tripods, and accessories from Swift, Bushnell, Bogen, Nikon, Pentax, Zeiss, and Swarovski.
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