Sunglasses Essentials – How do you choose?Posted by Whole Earth | 05.10.2018
So you’re ready to buy a pair of good quality sunglasses, but now that the search has begun, it’s become quite confusing. Sunglasses look fairly simple – frames and lenses, some colorful, others, not so much. But as you study the matter more closely, you discover a gaggle of new terms that are not necessarily self-explanatory. Fear not, Whole Earth is here to shed light on the terminology and give you a few pointers on choosing a pair of sunglasses for your life outdoors.
Let's start with lenses.
The most popular materials used to make sunglass lenses are glass, CR-39, and polycarbonates.
Glass has the best optical quality, is heavier, more resistant to scratches, and under impact can “spider.”
CR-39 has good optical quality, is half the weight of glass, can scratch, but has strong impact resistance.
Polycarbonates have good optical quality, weigh even less than CR-39, can scratch, but have the most impact resistance. This is a good choice for outdoor sports and activities.
Z-Resin is derived from castor bean oil and replaces traditional plastics in some sunglass frames and lenses.
ANSI is the American National Standard Institute. The organization oversees the development of standards for products sold in the US. Sunglasses standards are written by the Vision Council. When you see ANSI Z80.3…. in sunglasses descriptions, they refer to these standards.
Polarized lenses reduce reflected glare, the dazzling sunlight that bounces off hard, shiny and reflective surfaces like water and glass. Polarization results in sharper vision, more vivid color and greater depth perception.
Polarchromatic or photochromatic lenses darken or lighten in response to the intensity of the light. The changes are gradual allowing the eye to adjust. Polarchromatic lenses are polarized. Photochromatic lenses are not.
Gradient lenses fade from a darker tint on top to a lighter tint on the bottom allowing for comfortable vision over a wide range of distance and lighting conditions. They reduce glare for distance viewing while allowing you to see clearly for reading or close-up work.
Color lenses determine which portion of the light spectrum passes into the eye and can be especially useful under certain light conditions.
•Gray, blue and green lenses maintain true colors and are considered neutral lens options. They are best for bright sunlight.
•Copper colored lenses are good for medium and high light as they enhance contrast without significant color distortion. These lenses are often used by fisherman.
•Orange and yellow lenses increase contrast and depth perception, but also increase color distortion. They work well in low light situations or on stormy days. These lenses are often used by pilots, fisherman, hunters, marksmen and boaters.
•Rose colored glasses are not just for optimists. They work well in low light conditions and add a bit of contrast in flat light
Mirror coated lenses add a reflective coating to tinted lenses to further reduce the amount of light passing through to the eye. They are useful in very bright light conditions like sunlit snow.
UV protection is essential. Look for sunglasses that block 100% of UVA and UVB rays. Sometimes you will see this labeled as UV 400. All sunglasses sold by Whole Earth meet this standard. The color and darkness of sunglasses are not related to the ability to block UV. UV rays are not blocked by clouds, so sunglasses provide protection even on cloudy days.
VLT or Visible Light Transmission is a measure of how much light enters the eye. The higher the percentage of VLT, the lighter the tint. Low VLT, 8-15%, limits the direct light and glare from bright sun on snow and water and results in less eye strain. Higher VLT, 45-80%, would be useful in low light conditions.
Coatings are often added to more expensive sunglasses. These coatings can include hydrophobic and oleophobic coatings to repel water and oils, anti-scratch coatings for increased durability, anti-reflective coatings to reduce bounce back glare and angled light, and anti-fog coating for humid conditions or high-energy activities.
What about frames?
Frames are generally made of cellulose acetate, blended nylon, metal or a metal alloy.
Cellulose acetate is extremely lightweight and can be easily colored or dyed.
Blended nylon is strong and lightweight and is used for sports and performance frames. They are resistant to hot and cold and remain flexible, yet stiff. Wraparound frames are usually made of blended nylon.
Metal frames are more durable than cellulose acetate or blended nylon.
•Monel is a mixture of a broad range of metals and is the most widely used material in the manufacture of eyeglass frames. It is malleable and mostly corrosion-resistant, but can react to some skin chemistry types.
•Titanium is lightweight, durable, strong, corrosion-resistant and hypoallergenic. Sometimes frames are made of Titanium alloys and cost less than 100% Titanium frames.
•Beta-Titanium is created by heating Titanium to 860 degrees, making it denser, stronger and three times more expensive and standard Titanium frames.
•Beryllium frames are a lower cost alternative to Titanium. They are lightweight, strong and flexible and available in a wide variety of colors. They resist corrosion and tarnish making them an excellent choice for salt water environments.
•Stainless and surgical steel are also alternatives to Titanium. They are lightweight, strong, and if Nickel-free, hypoallergenic. They are readily available and reasonably priced.
•Flexon is a Titanium based alloy called a memory metal. Frames made of Flexon return to their original shape after twisting, bending or crushing. They are lightweight, hypoallergenic and corrosion-resistant.
•Aluminum frames are lightweight and highly corrosion-resistant and most often used in high-end frames. Pure Aluminum is soft, so frames are made of an alloy that contains small amounts of Silicon and Iron for strength and durability.
Hopefully, now that you have some familiarity with the terminology and benefits for quality sunglasses, you’re feeling more comfortable about choosing a pair that’s right for you. Need more help? Stop by one of our Whole Earth stores. We’d be glad to assist you.