How Sunglasses Work

Sunglasses

Sunglasses work by taking a lens material and modifying it to limit the amount of UV (Ultraviolet Radiation) that will reach the eyes of the wearer.

Today modern sunglasses have lenses made of many different materials, the most common being Glass, CR-39 Organic Plastic, Polycarbonate and Nylon.

Far and away the best lenses are made of glass because of it's distortion free quality and it's natural ability to block some UV radiation.

One of the draw backs of glass, however, is the fact that it is heavier than the other materials.

CR-39 plastic lenses come in second because of their ability to absorb tints to any degree desired. The scratch-resistant version of CR-39 is also an excellent choice for prescription lenses because of it's cost.

Polycarbonate lenses are more commonly used in sunglasses for those who participate in active sports like sport shooting, skiing and so on.

Nylon is a new entrant to the market and has many of the properties of the other lens materials.

 How Sunglasses Work

Sunglasses work by limiting the amount of UV light which is allowed to reach your eyes through the lenses.

Lenses need to be modified in different ways to achieve the desired performance desired.

For example, if you want lenses that are polarized you will modify them so that when the lens is rotated 90 degrees left or right it will eliminate 100% of the light reaching your eyes. But polarized lenses work very well for people who work near the water, snow or areas with buildings that have large glass fronts on them.

This is because those elements reflect the sun's rays at an angle which can pass right through a non-polarized lens and cause glare to irritate your eyes.

Lens Coatings

An example of coatings placed on sunglasses lenses

Sunglass lenses start as a lens puck that has been manufactured and is then placed into a curve generator to grind out the lens according to the manufacturer's specifications.

The lenses are then coated with a variety of wafer like sheets that have a number of different properties. For example the lens will normally have the following layers placed on it:

  • An anti-reflective back: this is a layer placed on the lens's back to protect your eye from the glare of light behind you;
  • A tinting layer: various lens tint choices are available; however the very best sunglasses tint is gray because is is best for viewing true colors;
  • A UV coating: this is perhaps one of the most important layers as it will filter our UVA and UVB ultraviolet radiation preventing them from reaching your eyes;
  • Another anti-reflective coating: this coating is placed on the front of the sunglasses lens to reduce glare and in some cases to even repel water;
  • A scratch-resistant coating: this coating is usually made from ultrathin Teflon polymer which is a durable type of plastic that prevents scratches on the surface of the lens;
  • A polarizing filter: if you spend a great deal of time on the water, snow fields or the desert than polarized sunglasses are a necessity for you.

Glare Reduction

Sunglasses work to reduce glare from entering your eyes and causing you to be distracted by by placing anti-reflective coatings on both the front and back of the lens.

This coating is different and separate from other coatings like lens tint etc.

Glare comes from many different places and is usually temporary in nature as you move.

High end sunglasses will have both of these coatings on them; however, there are no industry standard requirements for manufacturers regarding these anti-reflective coatings, and inexpensive sunglasses will likely not have them because of the additional costs.

Sunglasses Lens Tints

Sunglasses manufacturers can tint sunglasses lens with any color imaginable; however when it comes to understanding how sunglasses work you need to consider what your goal is in purchasing a pair of sunglasses.

Generally speaking sunglasses with tints like reds, blues, etc. may provide you with a great fashion statement; however, those tints may not provide much in the way of visual acuity for seeing things clearly.

Neutral Gray is always the best choice in lens tint because it allows true colors to pass through the lens and reach your eyes.

Sometimes you may need more than one pair of sunglasses because different lens tints work best for different lighting conditions.

For example, for normal conditions neutral gray will work best; however, for snow, fog or rain a tan or yellow tint will perform better. Copper, orange, yellow and brown lenses tints will enhance contrast in low light conditions.

What Sunglass Lens Tints Don't Do

Lens tint or darkness has nothing to do with how well your sunglasses protect your eyes from ultraviolet radiation.

The tint simply determines the amount of light that will reach your eyes and not the intesity of the UV radiation reaching your eyes.

This is another thing to think about when considering how sunglasses work.

So How Do Sunglasses Work?

Now that you understand how sunglasses are made we can discuss how sunglasses work.

Basically sunglasses work through the use of various coatings on the sunglasses lenses which perform different tasks from filtering out light waves and protecting your eyes from dangerous ultraviolet light rays.

In addition to the proper coatings being applied to the sunglasses lenses the way glass lenses are ground and the material they are made of are important in terms of how well the visual acuity is for you the wearer.

Mineral glass lenses are the best for glass lenses but they are slightly heavier than polycarbonate lenses. In addition, glass lenses will reflect heat while polycarbonate lenses absorb heat making glass lenses cooler to wear for long periods of time.

An Excellent Choice

When it comes to high quality sunglasses that meet all of the requirements above I recommend either AO Original Pilot Sunglasses or Randolph Engineering Sunglasses.

The bestuse mineral glass lenses, have the proper coatings, and have great style, comfort and performance. Take a few moments to look through our website at the various choices of Randolph Engineering sunglasses we offer, and in particular the Randolph Aviator Sunglasses.

Keep your eyes cool and protected today my friend! 

 John M. White a/k/a JetAviator7

How Sunglasses Work

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