UV lens also known as Ultra Violet. It is usually colorless and transparent, but in some viewing angle will show purple or purple-red because some have added the antireflective film. Many people buy UV lens to protect the precious lens coating, in fact, this is just one of its subsidiary functions. The main function of UV lens is used to absorb the wavelength of ultraviolet radiation below 400 nm, while no filtering effect to the other visible / not visible light. It was able to filter the ultraviolet rays because the lenses contain lead, so UV lens is heavier than other lenses the same size and thickness.
UV lens is for environment such as the sea, mountains, snowy, and open areas to photography, because can weaken a result of UV-induced blue hue. At the same time for the digital camera is, you can also exclude the interference of UV on the CCD and help improve the clarity and color reproduction results.
Choosing UV lens, we need to note that the lens will not color cast, and the camera after installing the filter, in particular in wide-angle side, able to focus clearly. In addition, if only in order to protect the camera lens from harm, you can also purchase a special lens to replace the UV lens. As lens protection lens adopt the multi-layer lens coating technology, the transmittance is much better than most of the UV lens, and thus able to fully retain the original characteristics of the lens.
How to identify:
Identification of UV method of fine quality is very easy. Take the UV lens as mirror on a black background. It is a good lens if photos nothing. UV lens grade are low if be able to illuminate the shadow of their own.