WHAT
TO LOOK FOR WHEN BUYING BINOCULARS:
Binoculars are used for a multitude of outdoor
& indoor activities. From sporting events, to bird-watching,
no matter what activity you use them for, they will always
be used to improve your view of distant objects.
How you plan to use your binoculars, and when
and where, are critical to the selection process. It's important
to evaluate binocular features so you may determine which
are important to you.
Magnification:
Every pair of binoculars has a reference number
that tells you its magnification power. An example would
be 8 x 42. The number "8" refers to how many times
the binoculars will magnify an object; in this case, it
will appear 8 times closer than it actually is. As a general
rule, higher magnification will make it more difficult to
pick up moving objects.
Lens Diameter:
The number "42" of 8 x 42 indicates the diameter
of the front of the binoculars, or the "objective lens".
The objective lens gathers the light that will eventually
reach your eyes. In general, a larger objective lens means
more light will be let in the viewing area, also known as
the field of view. A larger lens diameter, however, does
mean a heavier pair of binoculars.
Brightness:
Binoculars come with a variety of brightness levels; this
is essentially the amount of light your binoculars let in.
The primary deciding factor in determining brightness is
the size of the exit pupil, which is the size of the beam
of light your binoculars allow in. A larger exit pupil will
allow light to enter, which is a benefit if you plan to
use your binoculars in lower light conditions but not desirable
if they will be used outdoors in the sunshine. To determine
the size of the exit pupil, divide the lens diameter by
the magnification power.
Field of View:
This is the measure of how much you can see through your
binoculars at 1000 yards. Generally, the higher the magnification,
the less the field of view.
Prisms:
The purpose of a prism in binoculars is to correct the inverted
and reversed images you would see in their absence. The
prisms are located inside the binoculars and they transmit
light from the objective lens to the eyepiece. Binoculars
come in prism designs: "porro" prism and "roof"
prism. A "porro" prism offsets the eyepieces from
the objective lens to allow more brightness to be let in.
However, this makes the binoculars larger. A "roof"
prism aligns the lenses in a straight configuration, which
makes the design smaller. This preferred size is a consideration,
but the image is not as bright as with a "porro"
prism.
Focus:
There are generally three focus features on each pair of
binoculars. Some binoculars offer fixed focus, which is
convenient but loses the ability to alter the focus for
personal needs. A center knob lets you focus both barrels
at the same time. The right diopter ring, located on the
right eyepiece, allows you to customize your focus for each
eye. Binoculars are also ranked on near-focus distance,
which is simply how far away you must be from your subject
before it can be properly focused. The general range is
10-40 feet.
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