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Anti-reflective Coating
A common problem with sunglasses is called back-glare. This is light that hits the back of the lenses and bounces into the eyes.
The purpose of an anti-reflective (AR) coating is to reduce these reflections.
It consist of several layers of metal oxides applied to the front and back lens surface. Because of the layering effect, AR coatings sometimes have a hint of
green or purple colour, depending on the individual manufacturers process. Each layer is calculated to block reflected light resulting in a reduction in glare,
annoying reflections and halos around light sources. These coatings are particularly effective for reducing eye fatigue for computer operators and
anyone driving at night. And, of course, AR lenses enhance appearance by removing all distracting reflections.
Scratch-Resistant
Light weight hard resin lenses can be more easily scratched than glass lenses. Special coatings have been developed to help protect lenses
from normal scratching, and most of the newest lens materials include scratch resistant coating.
Mirror or Flash
Well with mirrored lenses they have a reflective effect to give a mirrored look the lenses have a very thin reflective coating,
which is sometimes called half-silvered surface, the half-silvered surface will reflect half of the light that strikes its surface,
while letting the other half go past straight through.
The mirrored lenses can absorb anywhere from 10% to 60% more light than uncoated lenses and additional protection from light
straight ahead, they are good for altitudes, sand, water and snow, to help with high reflections and reduces a large amount of light that reaches your eyes.
The mirror coating is sometimes applied as a gradient colour that gradually changes from top to bottom, darker to lighter, sometimes the gradually
colour is only made put on half of the lense, sometimes called bi-gradient, so your eyes are protected from light above and below so you can see more
clearly at the bottom.
With mirrored lenses the main problem is that the coatings are easily scratched, this is because as the manufacturers have not
been able to successfully apply a scratch-resistant layer on top of the reflective coating, the only way it can be done at the moment is by applying
the scratch-resistant coating first to protect the lenses then the reflective coating.
Photocromic sunglasses
Sun-sensitive lenses are also called “photochromic” and “transition”.
These are lenses that darken as you go from indoors to outdoors. They are available in glass, hard resin and polycarbonate.
Originally made to darken to a moderate shade, new versions are available that darken to a true sunglass. Ask for a demonstration of these lenses.
Use note: Because photochromic lenses react to UV light and not to visible light, there are circumstances under which the darkening will not occur.
A perfect example of this is when you're in your car. Because the windshield blocks out most of the UV light, photochromic lenses will not darken
inside the car. For this reason, most sunglasses with photochromic lenses also have a certain amount of tint already applied to them.
Polarized sunglasses
These are the exciting sunglasses that eliminate reflected glare. They are especially appropriate for drivers, fisherman, hunters and all
types of outdoors activities. Light reflected from surfaces like a flat road or smooth water is generally horizontally polarized. This horizontally polarized
light is blocked by the vertically oriented polarizers in the lenses. The result: a reduction in annoying and sometimes dangerous glare.
The bottom line is that whether you spend your time boating or waterskiing, in-line skating or mountain biking, driving at night or jogging at noon,
polarized sunglasses are an excellent choice for sun wear.
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