The American sunglass industry has done a good job of regulating itself, although some of their advertising is a bit grandiose. Still the sunglass industry has not stepped beyond those claims made by plenty of other industries.
In this article I address how sunglasses can help with reflections. Some sunglass producers tout elimination of 100% of reflections from water, ice, glass, stainless steel, sterling silver, your uncle’s bald head, and possibly even reflections of poor personal character.
Reflections can only be canceled by polarization. That’s not to say that other suppression of reflected light are impossible, but complete elimination of reflections from wet roads can only happen with polarization.
Light is composed of waves coming at you in all directions, 360 degrees. So if you could see normal light wave fronts approaching you it would look like a star with an infinite number of points.
When light is reflected it becomes polarized, oscillating in only one direction – not an infinite number of directions. A lens polarized in the opposite direction can eliminate that wave of directional reflected light.
There is an interesting caveat. Total elimination of reflected light from a surface only happens at one exact angle of reflection, and that angle is different for every surface material. This means glass has a different “polarization angle” than water, which is different than plastic also different than metal.
So how well can Polaroid lenses work if they are only functional at one angle of reflection for each kind of reflective surface? There is partial polarization for every other angle proportional to the distance from the polarization angle. Ninety degrees from the angle there is 0% polarization. At 45 degrees there is 50% polarization. A polarized lens will cancel at the same percentage. Kind-of-a confusing concept, but it’s logical to estimate that polarized lenses get rid of about 50% of all reflection. Now if you add to that the suppression of light provided by coloration of the lenses then one can understand that polarizing lenses are very beneficial in high reflection situations. As a fly fisherman it can mean the difference between a good day and bad. If you are driving on wet March highways at the rate of 90 fps the distance lost in a blink is 13 yards. The distance of “flash recovery” from a blast of reflected sunlight can be 30 to 90 yards – possibly the difference between life and death.