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.
Types of Binoculars
Fixed focus
and
zoom
binoculars are alternatives to standard binoculars, which traditionally
offer magnification in one set power only, with a wheel or knob used to engage the focus mechanism.
Fixed focus
binoculars cannot be adjusted and are usually fixed at an average distance for use in
concerts, opera, or any situation in which variable focusing on objects is not required.
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