UV filter
Encyclopedia
- See also: UV water disinfection
UV filters are individual compounds or mixtures to prevent ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
(UV) light from getting through. UV filters are used in sunscreens to protect skin or in photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
to reduce the level of ultraviolet light that strikes the recording medium.
A typical UV filter in photography is transparent to visible light while filtering out shorter ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
wavelengths. Historically, some photographic films were sensitive to UV light, which caused haziness or fogginess, particularly with a blue hue. However, newer photographic film and digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
s are highly insensitive to UV wavelengths. UV filters are sometimes referred to as L37 or L39 filters, depending on the wavelength of light that they filter out; an L37 filter removes ultraviolet light with a wavelength shorter than 370nm, whereas an L39 filter eliminates light with a wavelength shorter than 390nm.
Many photographers still use UV filters as protection for their lenses, due to their low cost and lack of effect on the exposure of the shot. However, UV filters (in particular filters lacking optical coating
Optical coating
An optical coating is one or more thin layers of material deposited on an optical component such as a lens or mirror, which alters the way in which the optic reflects and transmits light. One type of optical coating is an antireflection coating, which reduces unwanted reflections from surfaces, and...
) may introduce lens flare
Lens flare
Lens flare is the light scattered in lens systems through generally unwanted image formation mechanisms, such as internal reflection and scattering from material inhomogeneities in the lens. These mechanisms differ from the intended image formation mechanism that depends on refraction of the image...
and have an adverse impact on contrast and sharpness, especially when a strong light source is present.