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Several factors determine the optical performance of a
binocular. They perform to the maximum only when all
these parameters are optimally calibrated and in harmony
with each other.
Magnification
The value indicates how much closer an object appears
through the binocular. The higher the magnification, the
closer the object appears. However, similar to a photo-
graphic zoom lens, a higher magnification narrows the
field of view. With an 8x44 binocular, objects will appear to
be eight times closer than with your naked eyes.
Objective lens diameter
This number affects the objective lens surface area through
which light enters the binocular. The larger the objective
lens, the more light that is able to get into the binocular. Your
image will be brighter in low light conditions. With an
8x44 binocular the objective lens diameter is 44 millimeters.
Field of view
The size of a binocular's field of view is stated in feet or as
an angle and uses the value of reference at 1,000 yards. If
your binoculars offer you a field of view of 390, then you
will be able to see a 390 feet wide image at the distance of
1,000 yards.
exit pupil
Look through your binoculars and then move it about
12 inches away from your eyes. You will see a bright circle
within the oculars. This dictates how much light that gets
to your eye. The exit pupil is measured in millimeters (mm)
and is a crucial indicator for low-light performance of a bino-
cular. A human pupil can open up to 7 mm in low light and
accordingly, binoculars that are used in low-light condi-
tions should
offer a large
exit pupil.
getting the MOst FrOM yOur steiners
formula for Exit pupil:
Exit pupil =
Objective lens Diameter
Magnification
