Jul

28

How polarized sunglasses work

Filed Under Eyewear Knowledge 

Polarization is the principle of glare moving on horizontal planes. Essentially, light is reflected horizontally. For example, look at the surface of a calm lake on a sunny day, often the lake will appear white, and you cannot see the stones and fish beneath the surface—this is caused by horizontal polarization.

polarized

Polarized lenses are unique in that they reduce light from glare without decreasing the intensity of your entire line of site, meaning you’ll more easily be able to see below the surface of the lake. Polarized lenses block all types of glare, from water to mirrors to windows to the reflection of light on metal (cars, for example). Therefore, polarized lenses are especially helpful when driving, fishing or playing any sport where there is metal that could potentially direct a blinding glare into your eyes (golf, tennis). Because they block glare they are also much better for your eyes, and offer a clearer overall image.

An additional benefit of polarized sunglasses is that they do not simply block the amount of light reaching your eye—instead they block harmful reflections and glare while only minimally tinting your vision (though still around a 50% light reduction). Therefore, a clear, beautiful day with polarized lenses will block unwanted glare and reflections, but may also slightly darken the overall image.

            Arguments abound about the safety of polarized lenses in snow sports. Some claim that the lenses reduce glare to such an extent that it becomes difficult to distinguish between snow and ice. Other arguments hold that glare on the surface of choppy water helps sailors and fishermen gauge how dangerous the waves are, and how rapidly wind is changing based on the glare changes in wave ridges. However, one would simply advise the fishermen to wear them on calm waters (to see below the surface) and remove them on choppy seas.

            Additionally, there have been reports that LCD lights are hard to see or invisible when wearing polarized sunglasses. One wonders why anyone would watch TV in the sunshine. However, this does apply to LCD screens mounted in your car, which could be quite annoying.

polarized            There are several ways to tell if your sunglasses are polarized. You can consult the company of origin, naturally, or you can test your sunglasses manually. Look through your lenses (holding them in your hands away from your face) at a window, TV screen or lake with intense glare. Rotate the glasses in a circle facing the glare. The intensity of the glare should change when you rotate your glasses. This is because glasses are meant to be worn in a certain way (on your nose) so the lenses are intentionally polarized vertically, which is how horizontal glare is reduced. When you rotate your lenses you are moving a vertical polarization off its vertical axis, and thus decreasing the efficiency of the polarization.

            It is highly recommend that people suffering migraines or eye aches from exposure to light purchase a pair of polarized sunglasses. Often, light-eyed people complain of glares and reflections that are sudden and piercing, but dark-eyed people hardly register the flash or light. These splashes of light can be detrimental to the health of your eye, and indeed, reoccurring headaches caused from outdoor light can be greatly reduced with polarized lenses. 

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