The choose and buy sunglasses?
Sunglasses, also called sunshade lens, and used as shade. People usually take in the sun by adjusting the pupil size to adjust the luminous flux, when more than the human eye light intensity adjustment ability, will cause harm to the human eye. So in the outdoor activity places, especially in the summer, many people are shading mirror is used to keep out sunshine, to relieve his eyes to adjust the damage caused by fatigue or strong light stimulation. When buying sunglasses must check whether this pair of sunglasses can absorb ultraviolet UV plus 99% film lens, and then to check the transmittance of visible light are in good condition, good transmittance glasses on the vision can make the scene look more clear. Many people think that the deeper the lens color can prevent ultraviolet damage to the eyes, but this view is wrong. If the color of the lens, through the less light is certainly, through the less the amount of light, the pupil will become the greater the amount of incident resulting in uv more. So the color depth of lenses is 75% ~ 80% is appropriate, color depth here refers to wear sunglasses after the extent to which others can see your eyes. If the lens color too deep, people are hard to see you in the eye. So, the color depth of lenses is 75% ~ 80%. From what has been discussed above, we can know that as long as wear glasses can check its quality.
related: sunglasses polarized sunglasses