HOW TO CHOOSE THE RIGHT MARINE BINOCULAR There are many different kinds of binoculars available for on-the-water
use. Selecting a marine binocular that’s right for you will depend
upon your specific requirements, budget and other variables. If your
goal is to spot distant diving birds or floating kelp paddies, for example,
chances are you’ll need a higher level of magnification than you
would for general safety use. When choosing binoculars for boating or
fishing, there are some important general features and functions you’ll
want to look for. While a traditional model may fit the bill, serious
boaters and anglers may want to spring for advanced innovations such
as "gyro-stabilization," which provide significant advantages
for marine use. Regardless of what you have to spend on marine binoculars,
the following tips will help make a better-informed purchasing decision.
Magnification
Most experts agree that 7x (seven times) magnification is the most appropriate
for marine use. This level is generally considered to by the maximum
strength for use at sea, primarily due to boat movement. Boaters also
need to decide on an objective lens (the wide lens at the far end of
the binocular) that’s best suited for the job. For most marine
assignments, a lens with a 50mm diameter is best. These two elements
form a basis for the size of most binoculars designed for marine use
(7x50). A 7x50 combination allows for a steady image as well as the
maximum diameter of transmitted light that can be accepted by the human
eye. Smaller objective lens sizes are available, but while these may
be fine for daylight use, they do not provide the same capability for
distinguishing objects and colors in lower light conditions.
Waterproofing
Just because a binocular has a rubber coating, doesn’t make it
waterproof. A rubber covering simply help make the unit easier to grip
and protects it from wear and tear. To be totally waterproof, it must
be nitrogen-filled. This is typically indicated on the binocular. For
boating situations, waterproof binoculars are a must. If your binoculars
are not completely sealed and waterproof, they will be extremely vulnerable
to the sea-spray and moisture of the marine environment. Any water that
gets inside will lead to mildew on the lenses and prisms, severely affecting
overall performance. Waterproof binoculars keep out the surrounding
air and moisture, stabilizing conditions within and preventing condensation.
While binoculars with waterproofing may be more expensive, the extra
investment is definitely worthwhile for serious boaters and fishermen.
Field of View
Your field of view, which refers to the extent of the view you have
through the glasses at a distance of 1000m, is also an important factor.
Generally speaking, better binoculars will show you a circle with a
diameter of about 300 to 400 feet at this distance. This is important
because, when you bring the binoculars up to your eyes, you don’t
want to spend a lot of time searching around for your target. The greater
the field of view, the easier it is to scan the horizon or view moving
objects, such as a distant school of game fish chasing bait.
Gyro-Stabilization
This innovative system removes up to 98% of the motion due to platform
vibration or hand tremor-a common problem associated with high-power
binoculars. If you are a serious boater or angler, the higher price
tag for waterproof, gyro-stabilized binoculars may be justified. Equipped
with this feature, you’ll be able to zero in on targets more easily
as you motor along, despite the swells and chop. When vibration and
motion are present, gyro-stabilized binoculars allow the target to be
viewed easily with less fatigue. This is possible thanks to special
internal prisms on free-swinging and rotating gimbal frames, held stable
with high-speed gyro motors. Gyro-stabilized binoculars are available
in different sizes and with varying magnification levels. The price
tag is considerably higher for a gyro-stabilized model, but for serious
anglers seeking to zero in quickly on far-away signs of game fish, these
binoculars are well worth the investment.
Exit Pupil
The exit pupil it the measure of the aperture that lets light through
to the eye. A large exit pupil allows for a bright image that’s
ideal for viewing under low light conditions, such as those at dawn
or dusk. By dividing the objective lens diameter with the magnification
level of the binoculars, the exit pupil is obtained. For example, a
7x35 binocular has an exit pupil of 5 millimeters (35/7 =5). In simple
terms, you’ll want to purchase marine binoculars with an objective
lens diameter that is between four and five times the magnification.
Lens Coatings
Whereas early binoculars only transmitted about 50% of the light
received, today’s most advanced models allow up to 95% light
transmission. This means that of the light that hits the objective lens,
95% is passed through to the viewer's eye. Generally speaking, most
quality binoculars on the market today deliver a light transmission
of 70 to 80 percent. Some binoculars also feature special lens coatings
that reduce stray light (reflection) within the binoculars for a brighter,
sharper image. There are also lens coatings available that filter out
harmful UV and IR radiation.
Prism Systems
Binoculars are available with two different types of prism systems-the
traditional Porro prism system and the roof prism system. Since brightness
is a key consideration for on-the-water use, models with Porro Prism
Systems (which let in more light) are better for marine applications.
While roof prism models are typically light and compact, they don’t
function as well in low light conditions.
Bk-7 and Bak-4 Glass
These designations refer to glass quality. Bk-7 glass-the industry standard-is
typically used in simple binocular models. While this type of glass
can provide a quality image, Bak-4-which is composed of carefully selected
and machined Barium Crown glass- provides even better resolution of
details and a brighter image with high color fidelity.
Compasses
Many marine binoculars incorporate a compass reading into the view.
Such models typically feature a compass scale that’s viewable
at the top or lower portion of one of the lenses as you look through
the binoculars. This feature allows you to take a bearing while you
are looking at a buoy or marker.
If You Wear Vision-Correcting Glasses
Because vision-correcting glasses offset the distance of the eye to
the binocular lens, boaters that wear such glasses should choose binoculars
featuring soft rubber eyepieces that can be pushed in or folded down.
This will enable the "relief"-the distance between the ocular
lens and the user’s eye-to be correct, allowing for proper clarity
and sharpness. |
