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Basic binocular terminology – Carson Makalu 10x42 Binoculars User Manual

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Basic Binocular Terminology:

Binoculars are commonly identified using 2 sets of numbers. The most common size is
8x21mm. The “8” is the magnification and the “21” is the diameter of the objective lens
in millimeters.

Magnification:

Typically, binoculars range from 5x to 12x power. A 5x binocular means

that the image you see through the binocular is 5 times larger than it would be when
viewed with the naked eye. There are larger power binoculars available, and most
higher power binoculars are usually the variable type, also known as zoom binoculars.
A 20x–80x zoom binocular, for instance, has a magnification range from 20 to 80 power.

Objective Lens:

The objective lens (front lens) diameter is listed in millimeters. The

larger the lens, the more light can enter the binocular and the brighter the image will be.
However, binoculars with smaller lenses are more compact and portable.

Field-of-View:

(Also known as FOV) is the total width of the viewing area through your

binoculars from left to right. It is often measured in feet at 1,000 yards. For instance, if
you see “358 ft @ 1000 yds”, that means an object that is 358’ wide and a thousand
yards away will take up the entire viewing area of the binocular image you see.
Sometimes this measurement is listed in degrees and is referred to as Angle of View,
i.e. 8°. To convert to feet, multiply the number of degrees by 52.5 and you will get the
FOV. Example: If Angle of View is 8°, Field of View is 8 x 52.5 = 420’ @ 1,000 yds.

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