Binoculars Explained

Yes, the view is razor-sharp. It's the little things, though, that make good binos truly great.

Jun 1, 2004
Outside Magazine
2004 Buyer's Guide : Binoculars Explained

   Photo: Illustration by Steve Stankiewicz

 •  Binoculars are classified with two numbers: 8x32, 10x40, etc. The first refers to the magnification—how many times closer an object appears. For most of us, seven or eight power is perfect; serious naturalists may want ten. The second number is the diameter (in millimeters) of the front, or objective, lens. The bigger the lens, the wider their field of view—and the more the binos weigh.

 •  What size lenses do you need? Compact binoculars have objective lenses in the 18-to-25-millimeter range. Midsize binoculars are 30 to 35 millimeters, great for all-around use. Full-size binos have 40-to-50- millimeter lenses, for the brightest views.

 •  The diopter control corrects any vision difference between your eyes. Look at an object, close your right eye, and focus the glasses normally. Then repeat for your right eye, using the diopter control.

 •  To maximize light transmission, the best binoculars have coatings on both surfaces of all their lenses. Such glasses are "fully multicoated." Better models are also sealed against rain, and the best are nitrogen-filled to eliminate internal fogging. Check the specs for "phase-corrected prisms"—they have a coating to enhance contrast and color accuracy.

 •  If you must wear glasses while using binoculars, look for a pair with at least 15 millimeters of eye relief—the distance you can hold the eyecups away from your face and still have a full view.

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