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In order to assist you with sizing your new sunglasses purchase you will find in each advert 4 dimensions which relate to the 4 key sizes shown below.
A The overall external width of these glasses from hinge to hinge including frame
B The width of the lens excluding the frame plan view
C The height of the lens including frame
D The length of the leg from the hinge joint to the tip of the leg
Choosing The Right Lens Type
There are four things a good pair of sunglasses should do for you.
Lens Material and Quality. There are several types of material for lenses. Polycarbonate is a synthetic plastic that has great strength and is very lightweight. There is however two grades of polycarbonate the better being optical quality polycarbonate which is free from distortions of blemishes and have evenly distributed colour across each lens. Cheap sunglasses usually employ the lesser grade polycarbonate.
Lens Darkness. What you plan to use the sunglasses for determines the darkness and colour of the tint. For outdoor sports such as mountain climbing and snow skiing, you want a tint that blocks most light. For most purposes, like going to the beach or driving, look for a tint that absorbs 70-90% of light. Tints that offer less the 60% blockage are only good for fashion since they offer only mild protection.
Tints.
- Grey Tints. Are great all-purpose tints that reduce the overall amount of brightness with the least amount of colour distortion? Gray lenses offer good protection against glare, making them a good choice for driving and general use.
- Yellow and gold. Reduce the amount of blue light while allowing a larger percentage of other frequencies through. Blue light tends to bounce and scatter off a lot of objects and can create a glare called "blue haze". Since yellow eliminates blue light it has the effect of making everything bright and sharp. However this tint distorts colour perception, which makes it inappropriate for any activity that relies on accurate colour recognition.
- Green. Filters some blue light and reduces glare. Because green tints offer the highest contrast and greatest visual acuity of any tint, they are the most popular.
- Purple & Rose. Offer the best contrast of objects against a green or blue background. They make a good choice for hunting and water sports.
- Mirroring. Reflective sunglasses often have a mirrored look. The lenses in these have a reflective coating applied in a very thin layer. The surface will reflect about half of the light while allowing the other half through. They are good in very bright conditions and allow for good colour recognition with minimum distortion.
- POLARISED. Boaters and fishermen have used polarized sunglasses to reduce glare from the water that they spend so much time on. In the past few years, however, the benefits of polarized sunglasses have been realized by a variety of other outdoor sports enthusiasts as well as by drivers and general use wearers. The popularity of polarized lenses has increased dramatically, as has availability.
Besides boaters, people that benefit most from polarized sunglasses include skiers, golfers, bikers, and joggers, who enjoy a clearer view and elimination of glare. These sunglasses can be used for driving and in fact can reduce the glare that comes off a long, flat surface such as the hood of the car or the surface of a road. Polarized sunglasses can also be used indoors by light-sensitive people such as post-cataract surgery patients or by those exposed to bright light through windows. 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.Several of the most serious eye problems can be linked to one cause, UV light. UV is often separated into two categories based on frequency and wavelength of light; UVA & UVB.
Ultra-Violet Coating.
As a natural protection mechanism, the cornea of your eye absorbs all the UVB and most of the UVA light. But over time, this absorption can lead to cataracts. The small amount of UVA that gets past the cornea can eventually lead to macular degeneration, the leading cause of blindness in people over 65. Intense and prolonged exposure to UV radiation can cause either cancer of the eye or photokeratitis, which is basically sunburn of the eye. A good UV coating on your sunglasses can eliminate UV radiation and you should always look for 100% protection, which you get as standard on Red Frog products..
- Sunglasses provide protection from Ultraviolet rays in sunlight. Ultraviolet (UV) light damages the cornea and the retina of the eye. Good sunglasses can eliminate UV rays completely. For more information see our section below on (UV). Red Frog Sunglasses eliminate 100% of UVA & UVB . Sunglasses provide protection from intense light. When the eye receives too much light, it naturally closes the iris. Once it has closed the iris as far as it can, the next step is squinting. If there is still too much light, as there can be when sunlight is reflected off snow or water, the result is damage to the retina. Good sunglasses can block light entering the eyes by as much as 97% to avoid damage.
- Sunglasses provide protection from glare. Certain surfaces such as water can reflect a great deal of light and the bright spots can be distracting or can hide objects.
- Sunglasses can eliminate specific frequencies of light. Certain frequencies of light can blur vision and others enhance contrast. Choosing he right colour for your sunglass lenses lets them work better in specific situations (see the section on tints below)
