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Buying Binoculars

Whether you want binoculars for bird watching, general nature study, sports, or sightseeing, there are a number of factors to consider.

  • Magnification. How close the binoculars make a distant object seem is called "magnification." For example, magnification of 8X (often called "8 power") makes an object 80 feet away appear as if were only 10 feet away. Is more magnification better? Not necessarily. These is a downside to greater magnification:
    • Hand Tremor - no one can hold binoculars perfectly still. As magnification increases, you are more likely to notice that the image shakes. Windy conditions or on a boat (as in whale watching) only increases the problem.
    • Field of View - people with normal eyesight have a field of vision that radiates roughly 160 to 170 degrees in both the left-right and up-down dimensions. Most 7X binoculars have a field of under 9 degrees, which shrinks to about 5 degrees with 10X binoculars. With a smaller field of view it becomes harder to find an object, especially a moving one like a flying bird.
    • Depth of Field - people with normal eyesight (or good eyeglasses) can look off in the distance and see everything from a few feet away to the horizon with roughly equal clarity. With binoculars, once you focus on a distant object, other objects more than a few feet in front of or behind your subject will be out of focus. At greater magnification, the in-focus range usually becomes narrower.
    Therefore for most purposes, 7X or 8X binoculars are safer bets than 10X. Note, however, that field of view and depth of field can vary between instruments with the same magnification based on the quality of manufacture.
  • Size of Objective Lens. Binoculars are identified as "8X40" or "7X42" or "10X50," for example. The number before the X is the power, or magnification, and the second number is the diameter of the lens at the front of the binoculars in millimeters. The larger the front lens, the more light your binoculars will collect and the more detailed the image should be. Lens size around 40 is normally optimal. The largest you'll usually find is 50, generally in a 10X50 instrument. Compact binoculars with lenses smaller than 30 often give you too small an image to be worth considering.
  • Size, Weight and Comfort in Your Hands. Old-fashioned porro-prism binoculars (the lenses are set farther apart than the eyepieces) tend to be bulkier and heavier than roof-prism models (their lenses are aligned with the eyepieces). However, quality porros are are roughly one third the price of quality roof models.
  • Close Focus Capability. If you are interested in up-close views of small objects, like butterflies, look for binoculars that can give you a sharp look at things only a few feet away.
  • Weatherproofing. Higher-end models will be sealed from outside air that can fog interior surfaces in humid or rainy weather.
  • Eye Cups. To shade users' eyes against the sun, the eyepieces have either soft rubber or hard plastic cups. If you wear glasses, you must either roll down the soft rubber or push in the hard plastic to get your eyes closer to the eyepieces for an adequate view.
  • Other qualities to look for include
    • Ease of Focusing
    • Sharpness of Image
    • Trueness of Colors
    • Brightness of Image in Twilight
    • Glare-Reducing and Scratch-Resistant Lens Coatings
    • Durability (Shock Resistance)
Personal preference also plays a major role in choosing binoculars. After researching the features of binoculars, you are well advised to get some hands-on experience with various models, preferable out in the field, before deciding on which to buy.

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