More about polarised sunglasses
Polarized sunglasses were first invented by Polaroid in 1935. They differ to standard, non-polarized sunglass lenses by using a special film, either sandwiched between two other layers of the lens or, on lower cost models, applied to the front of a lens. This polarizing film eliminates the glare that reflects off a surface like a pavement, road, water or snow. Lightwaves from the sun travel in all directions but when sunlight strikes a surface (including water), it becomes concentrated – it is this polarised light that causes harsh glare. Non-polarized sunglasses only reduce the amount of light entering the eye; they don’t block glare. Polarised lenses block glare and allow only useful vertical light to enter so you can see more clearly. Glare makes it difficult and uncomfortable to see and can cause eye strain. It also distorts the true colour of objects and makes them harder to distinguish. With polarised sunglasses you get glare-free vision, clear contrasts, more natural colours and reduced eye fatigue. Prolonged exposure to glare on the water can cause eye strain, in turn leading to headaches. Glare also causes a mirror-effect on water. As a polarised lens will eliminate glare on the water, for fishing enthusiasts it means they can see down below the surface. See also our fishing sunglasses.
Although polarised lenses provide lots of vision benefits it is important to note that the majority of polarised lenses used in models costing under £50 are made from a material called TAC which is relatively thin and does not provide impact protection. For sports such as cricket and shooting where impact protection is important a polycarbonate lens is required.
Are all polarised lenses the same?
The short answer is no. As mentioned above, the vast majority of lower priced polarised sunglasses sold (typically under £50) use TAC as the lens material and the polarised film is on the front of the lens. This means over time it can scratch and eventually lose some of its polarising properties. On higher priced polarised sunglasses (typically above £50) the lens material is likely to be polycarbonate (or a similar material called Trivex). Here the polarised film is sandwiched between two layers of polycarbonate meaning the polarised film can never wear out.