Sunglasses are not trivial accessories, but are fundamental and essential in many situations: to the sea, in the mountains in the city. So not just for vanity, because their use is important to protect your eyes from the sun. For fashion or necessity, the glasses must have specific characteristics.
The Right Lenses
The main function of sunglasses, is to prevent risks and damage to the eye caused by light, such as conjunctivitis and cataracts. In fact, since 1995, it is imperative that the package of the glasses, owns the label that indicates the filtering power of the lens. This value must be understood in a scale ranging from 0 to 4.
The filtering power 0 is equal to zero, then follows the value 1, which protects glare. The power filter 2 and 3 are those of lenses for medium and high brightness, and then the value 4, recommended for situation’s brightness very strong, as for example, when you are on a glacier or on a white beach.
In addition to the filtering capacity of the sunglasses must have total protection, then protect not only from UVA, UVB but also by those, such as invisible, but they can cause a variety of ailments. The European Community considers that the lenses are more than just those that absorb 100% of the visible rays and 96% of UVB rays.
The eyes should be protected in all angles, so the prescription lenses, that dark above and light below, are not suggested. You have to know that the dark lenses do not necessarily guarantee superior protection and better than lighter lenses, and if they are under can also cause greater damage than the latter.
Then there are situations (such as driving a car) where, it is preferable to use sunglasses with a filter value is not too high, to avoid a distortion of the natural light.
Polarized Lenses
Polarized lenses are used to protect themselves from the phenomenon called polarization, where the light is reflected on the various surfaces, traveling in a two-dimensional (three-dimensional and not as usual), and troublesome due to the play of light.
The reverb, for example, is one of these, which causes an altered vision of colors fatiguing in this way the eyes. To construct these lenses using a technique that allows the passage exclusive of the vertical rays and blocks the horizontal ones, which are harmful for the view.
Polarized lenses improve the perception of contrasts and allow you to have a clear vision from afar, to give a greater color saturation so that the colors are perceived in a more natural and saturated. The view is less tiring and guarantee total protection from UV rays.
The abbreviation CR39 polarized lens is perfect because it means that parallel surfaces which do not alter the optical beam and are equipped with anti-reflective and scratch-resistant surface because they were built with very resistant material.
Most lenses are dark will most polarizing power and protection. The colors such as dark gray, dark brown and dark green are the ones that have a polarization ratio close to 100%.
This type of lens is used mainly by those who practice extreme sports, or skiers, snowboarders and sailors. Online you can find many brands of sunglasses with polarized lenses, but one that certainly have the best quality/price ratio is Polaroid.
The Materials Used
The sunglasses are differentiated from each other even for the material that is used in the lens and in the frame.
The lenses can be:
- Glass lenses : heavy but provide a much sharper.
- Plastic lenses : read and used in the majority of fashion eyewear, their weakness is that they scratch easily.
- Polycarbonate lenses : the most resistant to scratches and bumps.
The lens can then be of various colors :
- Gray lenses : attenuate the light and not deform.
- Lenses of brown and green : improve the contrast causing minimal color distortion.
- Lenses of orange color : those who have a better color contrast.
- Clear lenses : do not need to soften the light but to protect from UV rays.
As we have said before the lenses can be polarized and protect from UV rays, but there are also mirrored lenses with surfaces that reflect and are only partially filtered light. For the construction of the mount will use different materials:
- Metal frames : resistant and rigid.
- Nylon frames : lightweight, strong, and for this pie ghevoli They come to you or use you glasses sports.
- Plastic frames : lightweight, strong and flexible.
