Binoculars Information - How to Understand the Numbers on the Binoculars?
This page is a supplement to our How to choose binoculars article. | Binoculars
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BINOCULAR MAGNIFICATION (POWER)Binoculars are often referred to by two numbers separated with an "x". For example; 8x32. The first number is the power or magnification of the binocular. With an 8x32 binocular, the object being viewed appears to be eight times closer than you would see it with the unaided eye. We do NOT recommend to use binoculars with magnification over 10x without a tripod - if you go with too much magnification in a hand-held binocular, your image will be very shaky! Also, many people ask - How far can you see with a binocular? - we always answer - You can see as far your eyes can see, but the objects will seem to be closer - magnified by the power of your binoculars. Please see this page for some sample digital pictures taken through giant Oberwerk binoculars with 25x and 40x magnification. | |||||||
OBJECTIVE LENS SIZE (APERTURE) The second number in the formula (8x32) is the diameter of the objective or front lens. The larger the objective lens, the more light that enters the binocular, and the brighter the image.
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| Coated Optics
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| PC-3? Phase Coating | |||||||
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| Exit Pupil Refers to the size of the circle of light visible at the eyepiece of a binocular. The larger the exit pupil, the brighter the image. To determine the size, divide the objective lens diameter by the power (an 8x32 model has an exit pupil of 4mm). | |||||||
| EyeGlass Wearers - Eyecups Binoculars come with Twist-Up, Pop-Up or soft rubber Fold-Down eyecups which go down for eyeglass wearers. These options allow everyone to see the entire field of view. | |||||||
| Eye Relief The distance a binocular can be held away from the eye and still present the full field of view. Extended or long eye relief reduces eyestrain and is ideal for eyeglass wearers. | |||||||
| Field of View (F.O.V.) The side-to-side measurement of the circular viewing field or subject area. It is defined by the width in feet or meters of the area visible at 1000 yards or meters. A wide angle binocular features a wide field of view and is better for following action. Generally, the higher the magnification, the narrower the field of view. | |||||||
| Focusing SYSTEMS
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| I.P.D. (Inter-Pupillary Distance) The distance between the eyes differs from person to person. The adjustment for this difference is accomplished by opening or closing the hinged portion of the binocular to bring the eyepieces closer together or father apart. | |||||||
| Light Transmission Refers to the efficiency of an optic, or its ability to deliver the maximum amount of the light entering the objective lens to the eye. | |||||||
| Magnification (Power) Binoculars are often referred to by two numbers separated with an "x". For example: 8x32. The first number is the power or magnification of the binocular. With an 8x32 binocular, the object being viewed appears to be eight times closer than you would see it with the unaided eye. | |||||||
| Objective Lens Size The second number in the formula (8x32) is the diameter of the objective or front lens on binoculars. The larger the objective lens, the more light that enters the binocular, and the brighter the image. | |||||||
| Near or Close Focus The shortest distance at which the binocular is capable of providing a sharply focused image of an object. Especially of interest to birdwatchers and nature buffs. | |||||||
| Prism Glass Most optical prisms are made from borosilicate (BK-7) glass or barium crown (BAK-4) glass. BAK-4 is the higher quality glass yielding brighter images and high edge sharpness. | |||||||
| Prism SYSTEMS The prism system of a binocular reduces the size needed to provide focal length and turns what would be an upside-down image right-side-up. There are two types of prism systems, roof and porro.
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| XTRTM technology As light passes through the many prisms and lenses of a roof-prism binocular, some light is usually lost along the way. Bushnell's exclusive XTR technology - utilizing 60 layers of coating on each prism - conserves, harnesses and optimizes the available light. XTR delivers an amaizing 99.73% light transmission of 90%, making binocular the brightest in its class. | |||||||
| Resolution Resolution, or definition, is the ability of a binocular to distinguish fine detail and retain clarity. | |||||||
Waterproof/Fogproof
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| Zoom Binocular A binocular with a variable power range, for example: 8-20x. Magnification is changed with a convenient lever or knob allowing you to increase the magnification when you want to get in close for detail from a distance. | |||||||
| Bushnell Binoculars Manual is available for download here | |||||||






OBJECTIVE LENS SIZE (APERTURE) 





