Our guide to affordable binoculars, a glossary of binocular terms, and the dos and don'ts of buying binoculars.
Published: May 4, 2006
To identify distant birds accurately, a binocular is essential. Two basic designs are available: Porro prism and roof prism. In Porro binoculars, the light-gathering objective lenses are set wider apart than the lenses you look through. For years Porro binoculars set the standard for everyday use, being rugged and less expensive than roof prism binoculars, in which the eyepieces and objective lenses are aligned with each other. Roof prism binoculars generally weigh less than Porro types and are more water-resistant, but they tend to cost more.
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A binocular's name is typically followed by two numbers separated by an "x." The first number refers to the magnification or power of the lenses. Most birdwatchers use binoculars with a magnification between 7x and 10x. The higher the magnification, the closer the object appears in the field of view - and the more noticeable vibration from hand shake becomes as you try to hold the binocular steady. The lower magnification allows better viewing at close range (watching warblers, for instance), while greater magnification works better for picking out birds from a distance. For general-purpose viewing, binoculars with 8x magnification are becoming the choice of many birders today.
In general, the more light transmitted by your binocular, the better you will be able to see birds. Here's where the second number on the binocular (the one after the "x") comes into play. Divide that number by the first to determine the size, in millimeters, of the image that the binocular delivers to your eye. An exit pupil of 7.1 millimeters (found in a 7x50 binocular) is about the highest useful number - any bigger and it would exceed the size of your own pupil - and an exit pupil of 5 millimeters (found in 10x50, 8x40, and 7x35 binoculars) is very good. Light transmission is also determined by the type of glass used for the lenses and the number of coatings that have been applied to those lenses - the more the better. The best and most expensive binoculars contain BaK-4 glass and are fully multicoated to reduce stray light and to increase contrast.
|Dos and Don'ts|
Many camera and birding supply stores carry quality birding optics, as do the American Birding Association, selected outdoor outfitters, and a number of online and mail-order vendors. Before buying a binocular, read a review or two, ask other birdwatchers about their binoculars, and try out several models. Find an instrument that feels comfortable in your hands, works well with your eyeglasses (if you wear them), and is light enough for you to hold up for half a minute or more without your arms getting tired. A birding binocular will cost between $150 and $1,500. Purchase the best you can afford, and be careful when buying binoculars less than $75 in price. The quality of the glass and the durability of such models can be quite low and they are rarely water-resistant.
When birding in the field, situations often arise where greater magnification is needed than binoculars can provide. Enter the telescope, or spotting scope among birdwatchers. Spotting scopes come with magnifications above 20x, and some have zoom eyepieces that can boost the magnifying power up to 75x.
A seabird in flight over the ocean may appear as a speck to the unaided eye, but training a spotting scope on it will reveal the shape of the bird and other identifying marks.
Shorebirds, which often feed in large groups along mudflats and shorelines, can not be approached too closely for fear of chasing them off. A spotting scope becomes the essential tool for picking up the birds' subtle differences.
Want to take it one step further? Learn all about the art of digiscoping (taking digital photographs through a spotting scope), by reading our online article, "Making the Connection."