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Shape directly relates to how
easily and steadily binoculars
may be held, and this directly
affects image quality.
“Mini" binoculars, favored by
backpackers because of their
reduced size and weight, offer
little to anchor a shake-free
grip so birders generally avoid
them.
Large, bulky or “Marine"
binoculars force users to hold
their elbows high and widely
spaced, decreasing stability
and increasing muscle fatigue.
Birders avoid these, too.
Binocular Weight
Binoculars are literally a
weight around your neck. How
much you want to bear is up to
you, but in general, 20-30 oz. is
about as much as most people
care to consider.
The elements contributing to
the overall weight in a pair of
binoculars include:
s
the optical elements;
s
the body; and
s
the outer covering.
High quality optics, made of
barium crown glass (BAK-4),
are denser and heavier than
optics made of the cheaper
boro-silicate glass (BK-7). The
quality of the image you see is
directly related to the quality of
the optics.
To reduce overall weight,
quality binocular bodies are
cast out of aluminum or rugged
space age synthetics.
To help protect the internal
elements many binoculars are
“armored" – covered with shock
absorbing rubber or
polyurethane shell instead of a
leather-type or guttapercha
covering.
Focusing
Birding demands binoculars
that focus quickly. When
attention is diverted from a
close-at-hand warbler, to a
distant, fast disappearing
hawk, time spent spinning the
focus wheel to go the range of
focus is, well, time spent
spinning your wheels.
A binocular that can go
from close focus to infinity
quickly and smoothly is
invaluable in the birding arena.
Birding binoculars should be
center focusing binoculars. This
means that by moving a well
positioned wheel, both barrels
of a binocular are adjusted
quickly and simultaneously.
An individual eyepiece
adjustment ring (or knob) is
available to compensate for
the small differences that
exist between an individual’s
eyes. It is set once – then
never again.
Some military or marine
binoculars offer individual
eyepiece focusing – a system
that employs adjustable rings
that encircle both ocular
lenses. This system is slow,
cumbersome, and therefore, ill
suited for birding.
Some binoculars offer levers
instead of wheels for “quick
focus." These are appealing in
theory but in fact require a
two-handed grip and a bit of
dickering to get a sharp image.
They also tend to not be very
durable.
Some manufacturers also
offer permanent focus or non-
focusing binoculars. These would
be fine, if birds never
approached closer than 50 feet
– which is about as close as
permanent focusing binoculars
can offer a clear image.
But as birders know, birds do
appear closer than 50 feet. In
fact, sometimes – in cattail
marsh, dense woodlands, or
tropical forest, a bird might be
no more than ten feet away,
and because of poor light or
obstructing vegetation, an
identification cannot be made
with the naked eye.
At times like these a
binocular that offers super-
close focus may make the
difference between a Life Bird
or a shoulder shrug – which is
to say, all the difference in the
world.
Birding binoculars should be
able to focus down to 15 feet.
Binoculars that offer a close
focus down to nine or ten feet
are prized.
If you do a great deal of
woodland birding, or watch
birders coming to your feeders
at very close quarters, close
focusing binoculars are a must.
Magnification
Binoculars come in different
powers designated by the first
number of the binomial legend
etched on all binoculars
(examples: 8x30, 7x42, 10x42).
The second number refers to
the diameter of the objective
lens in millimeters and will be
discussed in the section dealing
with “Light and Brightness."
Simply put, a 8x binocular
(eight power) makes distant
objects appear eight times
