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 & 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 as
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 1,000 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 two
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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