Buyer's guide to sunglass lenses
Choosing the right sunglasses
Once upon a time, choosing which sunglasses lenses to buy was straightforward, but the sheer range of options today requires careful consideration before making that crucial choice.
Sunglass lens technology has advanced significantly in recent years, and new materials are continually entering the market, driven by significant advances in lens coatings.
Tinted lenses come in many colours, each with advantages and drawbacks in different lighting conditions.
Enhancements can include gradient tinting to help make lenses more dual-purpose and photochromic lenses that change shade to match various lighting levels.
Polarised lenses and specialist coatings increase the range and effectiveness of sunglass lens tints.
Tinted lenses can enhance vision
Tinted lenses are the most common choice and often the easiest to pick. Cosmetics will play a big part in your chosen lens shade. It is merely a matter of selecting the colour and tone depth that suits you best.
But there are some other considerations to take into account here. Much depends on the conditions in which you expect to wear sunglasses. Bright sunlight is the obvious candidate, but only sometimes. Individual colours can enhance vision under certain conditions, and the choice may not be purely cosmetic.
A light blue tint, for example, may look good outdoors, but it is not OK when glare is a factor, such as when sailing. A blue-tinted lens can increase glare outdoors, so choose this tint primarily for streetwear and city use.
For general outdoor holiday wear, brown-tinted sunglasses often make the best choice. Brown filters block blue glare from water and sky and can increase contrast. Brown is a popular choice for standard holiday sunglasses and general outdoor use.
Neutral grey is a popular choice
Grey is an excellent alternative to brown, retaining decent colour differential and reducing outdoor glare. A neutral grey tone is usually the most popular choice for the big outdoors and night driving.
Many also prefer a green-tinted sunglasses lens. Green lenses tend to be darker and are favoured by those with sensitive eyes. They can deliver the highest contrast and the right colour balance despite blocking out significant glare.
Yellow and orange tones are the most popular choices for snow sports, such as skiing and snowboarding. Yellow-tinted sunglasses soften the harsh white-blue light of pure snow while increasing colour contrast and depth perception.
Pink and rose-tinted sunglasses can help relieve eyestrain and are often used by people who spend long periods at computer screens. Colour perception may not be as accurate as other tints.
Graduated tints for reading
Many sunglasses carry a graduated tint in any of the above colours. The colour is strongest at the top of the lens, with graduated tones that fade progressively until it is nearly clear.
Graduated tint lenses are suitable for reading or for tasks requiring clarity when looking downward, while providing plenty of shade when the eyes are raised.
Photochromic gets a reaction
This type of sunglasses lens has a special coating that reacts to sunlight. Often referred to as transition lenses, they automatically darker as you move into the bright light and lighten when you head out of the sun.
The reaction time of photochromic lenses varies, but the transition typically begins within 60 seconds. They continue to darken or lighten for several minutes until they reach the optimal tint for the lighting conditions.
The coating is usually activated by ultraviolet light, which is invisible, so the darkening and lightening effect occurs even on cloudy days and depends only on the amount of UV light that reaches the lenses.
Photochromic lenses usually retain a small degree of tint, even in dark conditions. They can be useful for people moving between varying light conditions, such as indoors and outdoors. They are not used much for driving because headlights pass too quickly for them to react.
Even in daylight, the car windscreen can block UV light, so the photochromic lenses may be far less effective when driving.
Polarised lenses cut out glare
Popular with drivers and sailors, polarised lenses are particularly useful for reducing glare from large surfaces such as the sea and sky, with little or no loss of definition.
Unlike standard tint lenses that reduce light at any angle, polarised lenses block horizontal light waves while allowing vertical light waves to pass through. Polarisation reduces glare and improves depth and colour perception.
Vertically aligned light is more visually critical than horizontal rays, the central component of glare. The sun's glare on the sea and other flat surfaces can be highly polarised. In some conditions, it can be almost entirely horizontally polarised.
Likewise, the most reflected light is horizontal, and images appear clearer when this is filtered out by polarised sunglasses. They are especially suitable for driving, as bright reflections produce horizontally polarised light.
Polarising lenses provide clearer vision when driving, reducing dazzle and reducing eyestrain. However, take care when choosing. Cheap polarised lenses tend to block more light, sometimes as much as 10%.
