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The Basic Science:
Color is determined by a combination of
reflection and absorption of light
(either sunlight or artificial light).
Black would be maximum absorption while
white is maximum reflection. Bright sun
light (being reflected basically white)
bouncing off objects will hit our eye
from horizontal angles and can be too
much glare for our eyes to process. Flat
horizontal surfaces are reflecting
tremendous amounts of white glare. Water
is an almost flat horizontal surface
with the possibility of waves which can
act as many multiple horizontal surface
angles and even increase the glare.
When light strikes a surface, it
becomes polarized, which means
that the photons in the light
are all vibrating in one
direction, instead of in random
directions. The light waves
travel from "pole" to "pole"
along that plane. This
phenomenon is what causes the
glare reflected from a car
window or chrome, or from a wet
pavement. This glare distorts
the true color of objects and
makes them harder to
distinguish. It also causes a
mirror-effect on wet surfaces,
so that objects below the
water's surface cannot be
clearly distinguished.
How Polarized Sunglasses Work:
Think of the blinds on a window
at home. You can tilt the blind
at different angles to filter
the amount of light coming
through your window. The
polarized lens is designed with
filters at a 90 degree angle to
reduce vision of only the glare
but not the object.
Polarized lenses have a
laminated surface containing
vertical stripes. Similar to the
window blind, polarized
sunglasses will redirect and
scatter the glare making it
easier for you to see the
object.
Tradeoffs When Using Polarized Lenses: Although
polarized lenses do an incredible job of cutting
the glare in many outdoor activities, they do
have some minor drawbacks. When driving or
riding a motorcycle the light filtering
properties make seeing the readout on an LCD
instrument difficult. This can also include the
readout on cell phones, GPD devices and bank
teller machines.
In cases where instant decisions
need to be made and vision is
key in the decision like seeing
an instrument polarization can
become a problem. Another
unique example of this would be
downhill skiing where
immediately seeing the glare
from an ice patch and avoiding
that spot is critical. However,
there are very few examples that
I can imagine where cutting the
glare wouldn’t be more important
then being able to see it.
Quality Issues:
So what’s the difference between polarized
sunglasses and why do the prices vary so widely?
First, I would like to say that you don’t have
to purchase $200 polarized sunglasses to enjoy
the benefits of polarized sunglasses. I have
owned $15 polarized sunglasses that allowed me
to see well into the water and catch more fish
as a result. However, those $15 sunglasses did
have a few issues that I would have not had to
deal with if I had known a bit more about the
subject.
The first polarized lenses were made of a
polarizing film that was sandwiched between two
flat sheets of glass. Because glass lenses are
so heavy, however, the advent of plastic and
polycarbonate materials, which are lighter and
thinner, made the glass lenses less popular.
One of the problems with early polarized
sunglasses was referred to as “delamination”,
when the polarizing film separated from the
pieces of glass or plastic. This problem has
been solved with modern lenses, as the plastic
can be melted and poured into a mold in which
the polarizing film has been suspended. The
plastic then hardens around the film, creating a
solid material, rather than a layered one.
Polycarbonate lenses are created in a different
manner, since polycarbonate lenses are injection
molded and the heat from the process would
destroy the polarizing film. For polycarbonate
lenses, the polarizing film is applied to the
front of the lens and covered with a
scratch-resistant coating. This process means
that polarized polycarbonate lenses are the
thinnest and lightest polarized lenses
available.
Options:
I would like to offer these options for you to
consider when you are selecting the correct
polarized sunglasses for you. Only you can
determine how much you intend to wear these
polarized sunglasses, how critical seeing with
them might be and how careful you are with your
sunglasses. Taking these options into
consideration will help you determine how much
you will be willing to spend.
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