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Binoculars for Birders
You are a person who enjoys watching birds and
this puts you in good company. In the estimates of the United States Fish and
Wildlife Service, over sixty million North Americans have
discovered the pleasure and challenge of birding. Chances are, you already own a
pair of binoculars--a pair you inherited or bought without much thought; a pair
that has served, but maybe did not excel.
But now your are ready to
move up to quality optics...binoculars that will make it easy to get into those
hyperkinetic warblers and treetop vireos. You need binoculars that are sharp
enough to resolve the details that separate lookalike flycatchers and bright
enough to disclose the facial pattern of an "olive backed" thrush
stalking the shadows. In short you are ready to buy a pair of "birding
Why won't just any binocular do?
Binoculars are the primary tool for bird
watching. Different "User Groups" (hunters, yachtsmen, backpackers,
concert goers) use binoculars as an accessory to their activity or sport. But
binoculars are not just an accessory to birding. Binoculars are the instruments
that define birding--the functional equivalent of the first baseman's glove, the
musician's instrument, the plow in the hands of the frontier farmer.
Every user group has its own peculiar needs
and constraints that binocular manufacturers translate into binocular makes and
models. Hunters, for example, demand rugged, durable, optically precise
binoculars that perform well even in the low light conditions of dawn and dusk.
Yachtsman require optics that are impervious to weather. Backpackers want optics
that are light and portable.
But birders demand all these
attributes and more. For binoculars to be birder worthy, they must not only be
durable and precise, but also weatherproof and portable. They must focus fast
and focus close. They must offer a generous field of view and provide
exceptional depth of field even at close quarters. This article has one
objective: to give you the information you need to choose true birder worthy
binoculars and spotting scopes.
Forewarned is Forearmed.
There are several things you should know even
before talking to a salesperson.
FIRST--As a bird watcher, you represent the
largest "user group" in the optics market. Over 30% of all binoculars
purchased are used for birding.
SECOND--The needs and constraints of birding
are well known to binocular manufacturers but they might not be known to the
sales person you deal with. Chances are, after reading this article, you
will know much more about birding binoculars than any non-birding salesperson
you will meet. Don't let them confuse you.
THIRD--All equipment, including binoculars, is
designed to compensate for a human short-coming. People should never be forced
to compensate for their equipment. If the binocular you are considering is
flawed in performance or design (i.e. they do not focus close enough...they do
not fit your hands...the ocular lenses cannot be adjusted close
enough to offer a single image...) do not buy them!. If
you do buy them, you will only replace them later.
FOURTH--There are very cheap binoculars and
very expensive binoculars. There are binculars that are good for birding, and
binoculars that are not good for birding. There are no good cheap
birding binoculars. it takes quality materials and sophisticated
engineering to craft birder worthy binoculars. Expect to pay a commensurate
price--three to four hundred dollars at least.
What are binoculars?
are twin barreled telescopes whose barrels are aligned to fall on the same spot.
They are superior to a telescope insofar as they can be used with both eyes
open--making long term viewing easier. Since binoculars are usually hand held,
they are also more portable and faster to use than telescopes.
Binoculars are divided into two basic design
classes: Porro prism and Roof Prism.
Porro prism or "traditional binoculars" are wide-bodied. The big lens
in front (the objective lenses) and the smaller one in the back (the ocular
lenses) are offset--i.e. not aligned along a vertical axis.
prisms, which became popular in the late 60s and 70s are longer and sleeker in
design with the objective and ocular lenses falling in alignment along the same
Both designs have advantages and
disadvantages. Because Porro prism binoculars have fewer internal
"elements" (lenses and prisms) and more generous tolerance specs, they
are generally brighter, less expensive to manufacture, and less expensive to
repair in the event of a mishap. Roof prisms, though more expensive, also tend
to be more rugged with elements more firmly anchored within the barrels. Many
people also find Roof prism binoculars easier to hold steady for extended
The important thing about binocular
shape is how they feel in your hands.
If you grasp a pair of binoculars and bring them to your eyes and your finger
does not fall comfortably upon the focus wheel, or if you have to shift your
grip to move the focus wheel, then the binoculars are poorly designed or too
large for your hands. Put them back on the shelf.
Likewise, if you bring the binoculars up to
your eyes but find that you cannot draw the eyepieces close enough to offer a
single image, put them back on the shelf. The minimum "interpupillary
distance" offered by some models is simply not close enough to accommodate
people with closely-set eyes.
Shape directly relates to how easily and
steadily bioculars may be held and this directly affects image quality.
"Mini" binocualrs, 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.
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: the optical elements, the body, and the
outer covering. High quality optics, made of barium crown glass (BAK-4), are
denser and heavier than optics makde 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.
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 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 systme 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 fifty 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.
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 referes to the diameter of the objective
lens in milimeters and will be discussed in the section dealing with "Light
Simply put, a 8x binocular (eight power) makes
distant objects appear eight times closer than they really are; a 10x binocular
makes the object appear closer still--ten times closer.
The tendency is to believe that bigger is
better--that the more "power" a binocular has, the better it will
perform. This is not necessarily so and there are several reasons for
First, although higher magnification will
increase the size of a distant bird and enhances the details that will be seen,
increased magnification also magnifies the effects of hand shake and heart beat.
The image may well be bigger but details, as measured by image perception, will
remain essentially the same.
Greater magnification also results in a
smaller field of view, a darker image, and a shallower depth of field--all of
which directly affect binocular performance.
Almost all active birders use binoculars that
offer between 7x and 10x. What magnification you choose hinges on a number of
considerations. In general, lower magnification is to your advantiage if: (1)
you are a beginning birder, unpracticed at locating birds with binoculars; (2)
you are a birder having difficulty holding higher magnifications steady; (3)
much of your birding is conducted at close quarters in woodlands or rain forests
or from the deck of a moving boat; (4) you are a highly skilled birder more
interested in speed than in seeing "field marks" of birds you
recognize by their JIZ (general impression and shape).
Ten power binoculars get the nod if: (1) your
hands are steady; (2) most of your birding is conducted over great distance and
open spaces; (3) you do not commonly include a spotting scope in your optical
If you are still undecided between 7x or 10x
binoculars, consider a compromise--like an 8x but NEVER BUY A ZOOM BINOCULAR!
They are optically inferior and even at the lowest magnification, offer a
comparatively limited field of view. If you look at the optic lines offered by
the finest optical companies or if you look at the instruments in the hands of
the finaest field birders, you will never see a zoom binocular. This
should send a clear message to the discerning consumer.
Light and brightness
Once--and not long ago; and not without
reason--much was made about binoculars and brightness and light loss. Guides to
purchasing optics expounded upon the mysteries ot the "twilight
factor," and "relative brightness," and "relative light
efficiency." Sales people who know little about binoculars except, perhaps,
how to read charts still expound upon these mysteries.
Certainly a bright image, offering sharp
contrast and accurate color rendition is important to birders--in fact,
it is essential. The fact of the matter is that since the advent of coated
lenses...and multi-coated lenses...and phase coated Roof prisms...all the old
rules governing glass and light have been bent. If you are willing to pay the
price for quality binoculars, you are virtually assured of owning binoculars
that offer superior brightness.
The problem used to be this. Every time light
strikes polished glass (like a lens; like a prism) 5% of it is lost, reflected
away. In every binocular there are 10-16 glass surfaces whose cumulative loss of
light equalled about 50%. The net result was a dark image.
In partial conpensation, binocular
manufacturers could increase the size of the objective lens. The size of the
objective lens is measured in millimeters and appears as the second number of
the legend stamped on binoculars (example: 7x42, 8x30, 10x50). Larger objective
lenses allow more light to enter the binocular, increasing the diameter of the
shaft of light that exits the binocular to fall upon the human eye. This shaft
of light, seen as the bright dot swimming in the center of the ocular lens is
called the "exit pupil" and is still an important consideration when
buying optics. Here's why.
The human eye has a pupil, too--one that opens
and contracts in response to light conditions. In bright light it can expand to
about 7 mm (depending on your age) thus establishing the functional limit of the
binocular's exit pupil--because any light falling outside the maximum limit of
the human eye serves for nothing.
Beginning in World War II, it was discovered
that a coating of reflection reducing material (like magnesium fluoride) applied
to the surface of glass could reduce light loss caused by reflection from 5% to
almost 1%. This coating appears as a blue, or purple, or green glaze on the
lenses. Later it was discovered that by applying multiple, thin coatings instead
of a single coating, light loss could be further reduced to a mere fraction of
Recently, several manufacturers of superior
quality roof prism binoculars have begun coating the "Roof prism" with
a material that compensates for the modest wave length shift inherent in the
roof prism design with the result that "phase-corrected" roof prisms
offer the same sharp image contrast found in Porro prism binoculars.
The important consideration when buying
binoculars is to make sure the optics are "fully coated" or, better
still "fully multi-coated." The operative word is "fully"
because this means that all air to glass surfaces both inside the
binocular and out have been treated to reduce light loss. Different
manufacturers use different, patented names to distingquish their coatings. The
important thing is to be sure that all glass surfaces, inside and out, are
single or "multi-coated" to reduce light loss.
The process used to coat binoculars lenses is
exacting and costly. It accounts for much of the price difference between
quality binoculars and less expensive binoculars. But a commensurate price can
also be your assurance that your are buying binoculars that are bright and sharp
enough to perform in the field.
Field of View and Depth of Field
Field of view is the measure of the distance
from one side of a binocular's image to the other as seen through a stationary
binocular. This measurement, either inscribed on the binocular or included in
the accompanying literature, may be designated in degrees of arc (ex: 6, 7);
feet at 1,000 yards (ex: 415 feet at 1,000 yards); or meters at 1,000 meters.
However the measurement is noted, a wide
field--one that offers no less than 6 degrees of arc (or a minimum of 300 feet
at 1,000 yards) is essential to birding. A wide field makes it easier to pick up
and identify fast flying birds. It makes it possible to scan a sky, an ocean, or
an open marsh quickly. It's also easier to locate birds at close quarters in a
maze of branches.
Birding binoculars should also offer good
depth of field--a sharp, adjustment-free image from near to far. A generous
depth of field assists when trying to locate a close-at-hand bird in a maze of
brances. A generous depth of field mitigates the need to make focus adjustments
every time a bird moves a little closer or a little farther away.
Both field of view and depth of field are
closely related to magnification. In general binoculars with lower
magnifications offer greater depth of field, and a wider field of view than
binoculars with higher magnification.
Very closely related to field of view, Eye
relief refers to the distance between the ocular lens and the human eye. This
distance is measured in millimeters. Eye relief is a very important
consideration for birders who use eyeglasses in the field and who do not
remove their eyeglasses when fitting binoculars to their eyes. Because
the eyes of eyeglass wearers are already set 10-15 mm behind a glass barrier,
they demand a very "high" eye point--a binocular that offers a minimum
of 15 mm of eye relief. With rubber eyecups rolled down or otherwise retracted,
eyeglass wearers can enjoy the same wide field enjoyed by non-eyeglass wearers.
NOTE: Just because a pair of binoculars comes
with rubber eyecups does not mean they offer good or even aequate eye relief for
eyeglass wearers. The test is in the lenght of the actual eye relief.
Weather Resistance / Water Proof
Birding is an activity conducted outside and
from the moment a birder takes his or her binoculars outside, the outside is
trying to get inside those binoculars. In general "Internal Focusing"
binoculars are better sealed against dust, pollen ,and moisture than
"external focusing" binoculars. The tell the difference, move the
focus wheel and see whether or not the ocular bridge moves.
A very few superior binoculars are waterproof
(not "water resistant," not "weather resistant," not
"splash proof"). They are waterproof--able to withstand complete
emersion and remain dry inside. This is a difficult (and expensive boast) and
binoculars that really are waterproof/submersible will
certainly tout this.
You need not bird regularly in pouring rain to
appreciate the benefits of well built, well sealed optics. The day you jump from
your air conditioned car into a steamy Florida afternoon and train you now
completely fogged binoculars upon the swallow-tailed kite soaring overhead will
make you a convert.
Other Important Condiderations:
Whether you are a World Series of Birding
combatant, a rock climbing hawk watcher or a casual backyard birder who is
meticulously careful with equipment--accidents do happen. All birding binoculars
should be able to shrug off the occasional bump and ding. Superior binoculars
are impervious to airline baggage handlers, children, and tumbles onto pavement
precipitated by a combination of motion, gravity, and a fall to the roadway
after being left on the roof of a car.
Well constructed, well sealed, armored
binoculars offer another advantage. They need so special care--they don't even
need to be returned to a case after use! Hang them up on the hood by the back
door. Put them under the front seat of the car. They are there when you need
them. Ready at a moment's notice without having to run to the closet...and grab
the box from it's place on the top shelf (out of the reach of the kids)...and
open the case...and remove the binoculars...and extracte the plastic plugs that
protect the lenses...and run back to the kitchen window...to study the vibrating
branch where the bird (that just left) had been perched.
Lens protection is important so most
manufacturers of quality birding binoculars include custom fitted rain guards
with their optics package. Rain guards keep things like rain drops, salt spray,
sandwich drippings and hot breath from obscuring optics in the field. They also
keep dust off lenses when the binoculars are not in use. Some binoculars also
come with protective cups for the objective lens.
Binoculars should come with durable, supple,
and adjustable neck straps. Leather straps are chic but crack and rot under
normal field use. Plastic straps loose their suppleness in cold weather and will
loop when binoculars are raised--invariably falling directly between the ocular
lens and your eye. Most quality binoculars now come with straps made of braided
nylon. Wider straps help distribute weight evenly, saving wear and tear on a
Speaking of wear and tear, perfection is an
ideal that optics manufacturers strive for. Filling the gap between technical
precision and ideal perfection is the manufacturers equipment warranty. Quality
optics come with a warranty that covers materials and workmanship. Again, a very
few superior optics offer lifetime warranties to the original owner--a special
bonus for those who purchase optics designed and built to last a lifetime.
In time, after the birds of woodland and field
have been mastered and savored, many birders feel compelled to reach for the
horizon. They turn their identification skills upon migrating hawks, wintering
seabirds or feeding shorebirds. This kind of birding involves careful study over
great distances for extended periods and in this arena, a spotting scope is
Spotting scopes rest upon a tripod, a shoulder
stock, or specially designed window mount. Thus stabilized they make higher
magnification possible, bringing birds on the horizon within reach. Popular
powers include 20x, 30x, 40x and 60x. Zoom eyepieces are popular and do not, as
a rule, suffer the short-comings inherent in zoom binoculars. In fact, a few
spotting scopes with zoom eyepieces offer exceptional optical performance.
Like binoculars, spotting scopes come in a
range of quality and price and also like binoculars, you get what you pay for.
The Bottom Line
Birding is an activity that offers challenge,
excitement, and a lifetime of pleasure. The better your optics, the less
frustration you will know and more pleasure you will get out of birding.
When buying binoculars (and spotting scopes),
the rule of thumb is simple. Buy the best binoculars you can possibly afford and
buy them as soon as you can afford them. If you can't immediately afford the
quality binoculars you want, tolerate the ones you have or borrow a pair from a
friend. Save for the optics you really want. If you settle for less, you
will only regret your half-step purchase until the day you replace them with the
binoculars or spotting scope that you really wanted all along.
Good Birding! P.D.
About the Author...
Pete Dunne, of
the New Jersey Audubon Society, is one of birdings better known figures and
authorities on the optical needs of bird watchers. He is author of The Feather
Quest, Tales of a Low Rent Birder, and Hawks in Flight. His regular colums
appear in American Birds, Birding, and Living Bird. He and wife, Linda, live
near Cape May, New Jersey.
Swarovski Optik North America thanks Peter
Dunne for his time and effort in helping bring this article to you and the
Copyrite © 1996 Swarovski Optik K.G.
Copyright © 2010
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