UV filter

UV filters are individual compounds or mixtures that block or absorb ultraviolet (UV) light. Two major applications of UV filters are in sunscreens, where they protect the skin from sunburn and other damage, and in photography, where they are used to coat a glass disc which fits on top of the lens. These have become less necessary with digital cameras, as the medium is less sensitive to ultraviolet light. When exposed to UV light, these filters can undergo transformations into other chemicals that are less protective and possibly toxic. As a result, there are practical concerns about the choice of chemical to use beyond just which has the desired filtering properties. UV filters are individual compounds or mixtures that block or absorb ultraviolet (UV) light. Two major applications of UV filters are in sunscreens, where they protect the skin from sunburn and other damage, and in photography, where they are used to coat a glass disc which fits on top of the lens. These have become less necessary with digital cameras, as the medium is less sensitive to ultraviolet light. When exposed to UV light, these filters can undergo transformations into other chemicals that are less protective and possibly toxic. As a result, there are practical concerns about the choice of chemical to use beyond just which has the desired filtering properties. Historically, photographic films were mostly sensitive to UV light, which caused haziness or fogginess, and in color films a bluish hue. Therefore, as a standard, a UV (blocking) filter was used, transparent to visible light while filtering out shorter ultraviolet wavelengths. However, newer photographic film and digital cameras are highly insensitive to UV wavelengths. UV filters are sometimes referred to as L37 or L39 filters, depending on the wavelengths of light that they filter out; an L37 filter removes ultraviolet light with a wavelength shorter than 370 nanometers (nm), whereas an L39 filter eliminates light with a wavelength shorter than 390 nm. UV filters span the color spectrum and are used for a wide variety of applications. Ortho Red and Deep Ortho Red lights are commonly used in diffusion transfer, typesetting films/paper, and other applications dealing with orthochromatic materials. Yellow Gold, Yellow, Lithostar Yellow, and Fuji Yellow filters or safelights provide safe workspaces for contact proofing applications like screen printing and platemaking. Pan Green, Infrared Green, and Dark Green filters or safelights are commonly used in scanning applications, work with panchromatic film, and papers and x-rays. Many photographers and cinematographers still use UV filters as a protection for their lenses' glass and coating. However, UV filters, as with any filter may introduce lens flare and have an adverse impact on contrast and sharpness. Hoods offer some protection against impact and shade optical elements, preventing lens flare, but quality UV filters offer some protection against lens contamination while minimising the inherent additional distortion.