One is to prevent ultraviolet :UV is the wavelength emitted by the sun is 200--400 nm radiation ， it is also one of the shortest wavelengths of sunlight ， these rays are invisible to our eyes ， but it can make photographic film and other photosensitive material phenomenon occurs ， reducing the subject image vividness of the colors . This time we will be able to use a UV lens filter out UV rays， reduce transmission to the photosensitive material of blue-violet light， so that a clear vision to improve the contrast and color saturation far views. In some special occasions， such as altitude ， extremely intense ultraviolet radiation ， plus a UV lens or necessary .

The second is to protect the DC lens:As the majority of DC lenses are exposed ， it can easily be contaminated by dust， water ， oil or finger prints ， etc. ， which we need to frequently clean the lens ， and DC lens is very delicate ， once the cause is wear mirror it is difficult to recover， which will undoubtedly seriously affect the clarity and quality of the screen， in addition to use in peacetime contact careless collision with foreign matter ， will have irreversible consequences . Therefore， the installation of a transparent UV protective lenses on the outside of the lens to protect the lens will not be directly affected by contamination or damage. In other special occasions， such as water， moisture a lot of space ， the unexpected scene of the accident ， especially in harsh shooting environment or sandstorm weather ， due to many uncertain factors could cause the lens contamination ， then UV lens with a lens can be well protected .