If it's a bright, clear day outside, you may instinctively reach for your sunglasses when you head for the door. And you probably do it without much thought about them. But you probably do think about sunglasses when you go to buy a new pair -- whether you walk into the discount store or the Sunglass Hut at the mall, you are immediately struck by the bewildering array of choices before you! For instance, there are differences between tinted, reflective, photochromic and polarizing sunglasses. The style of the frame and size of the lenses also make a difference. Is that $200 pair of Serengeti sunglasses really any better than a $10 pair from the flea market?
Now, we'll take the mystery out of sunglasses and help you understand what to look for when you buy a pair. We'll analyze the different styles and look at the technology behind the different lens compositions. You will also learn how light works and see why light, in certain situations, can make sunglasses absolutely essential. You will be amazed at how complex and sophisticated a simple pair of dark glasses can be!
There are four things that a good pair of sunglasses should do for you:
- Sunglasses provide protection from ultraviolet rays in sunlight. Ultraviolet (UV) light damages the cornea and the retina. Good sunglasses can eliminate UV rays completely.
- 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 reflecting off of snow, the result is damage to the retina. Good sunglasses can block light entering the eyes by as much as 97 percent 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. Good sunglasses can completely eliminate this kind of glare using polarization (we'll discuss polarization later).
- Sunglasses eliminate specific frequencies of light. Certain frequencies of light can blur vision, and others can enhance contrast. Choosing the right color for your sunglasses lets them work better in specific situations.
So there is a difference. Buying the right pair of good sunglasses for the conditions in which you use them gives you maximum protection and performance.
The sidebar shows some of the top sunglass manufacturers. Manufacturers of other products sell sunglasses, too. From Nike and Timberland to Gucci and Kenneth Cole, many big brands include sunglasses among their product lines. Many sunglass manufacturers make huge claims about the features and special qualities of their products. Prices can range from less than $20 to several hundred dollars depending on the features and the name.
Then there are the imposters. You go to a discount shop or a flea market and see vendors offering sunglasses that look exactly the same as the high-dollar brand names for a fraction of the cost. Are you really paying that much for a name or are there fundamental differences between the look-alike sunglasses and the brand-name ones?
The biggest problem with cheap sunglasses is in the way the lenses are made. Inexpensive sunglasses have lenses made of ordinary plastic with a thin tinted coating on them. While the tint color and a similar frame design may make them look like Oakley X-Metal Romeos or Ray-Ban Predators, the actual lenses are very different. You will learn exactly how different they are, and how important the differences are, in the following sections.
- Lens material - There are several types of lens material. CR-39 is a plastic made from hard resin that meets optical quality standards. Polycarbonate is a synthetic plastic material that has great strength and is very lightweight. These lenses tend to be lighter and are more impact-resistant. Glass lenses are heavier but are much more resistant to scratches. There are several other materials, such as Oakley's Plutonite plastic, that have been developed by specific manufacturers.
- Lens quality - Optical-quality polycarbonate and glass lenses are free of distortions, such as blemishes or waves, and have evenly distributed color across each lens. Here's an easy way to tell if the lenses in a pair of sunglasses are of good quality. Find a surface with repeating lines, like a tiled floor. Hold the sunglasses a short distance away from your face and cover one eye. Look through one of the lenses at the lines while moving the sunglasses slowly from left to right and then up and down. The lines should stay straight as you look at them. If they wiggle or waver in any way, then the lenses are not optical quality and will distort your vision. Distortion is extremely common in cheap sunglasses.
- Lens darkness - What you plan to use the sunglasses for determines the darkness of the tint. For outdoor sports such as mountain climbing and snow-skiing, you want a tint that blocks most light. (You can buy sunglasses that block up to 97 percent of light!) For most purposes, like going to the beach or driving, look for a tint that absorbs or blocks 70 percent to 90 percent of light. Tints that offer less than 60-percent blockage are mainly good for fashion since they offer only mild protection.
- Special coatings or features - Anti-reflective, waterproof, mirror and scratch-resistant coatings improve the functionality of the sunglasses but also add cost. Many of the more expensive sunglasses use specific technologies to achieve increased clarity, better protection, higher contrast or to block certain types of light. The section on sunglass technologies discusses all of these features in detail, including polarization, tinting and anti-reflective coatings.
- Frame and lens design - Normal frames similar to prescription eyeglass frames filter the light coming through the lenses but offer no protection from ambient light, direct light and glare from other angles. Wrap-around frames, larger lenses and special sidereal attachments can keep this extra light from your eyes.
- Frame material - The material used to make the frames is often a huge factor in cost and durability. Most inexpensive sunglasses use simple plastic or wire frames, while name-brand sunglasses by companies like Revo, Maui Jim and Serengeti use high-strength, light-weight composite or metal frames. Also, the better sunglasses usually have features like tension springs that connect the arms to the face instead of just screws.
- Brand recognition - The simple truth is that a brand name does add cost. Just like shoes and suits, people associate certain brands with quality and extravagance. Some companies spend huge amounts of money to advertise a brand and create an identity. That cost is often passed on to the consumer in the product's price. If "brand name" is important to your image, then buying a brand name is important. However, it is possible to find high-quality sunglasses that don't have a brand-name price. A place like REI often sells store-brand glasses of good quality at a much lower price.
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