UV filter (photography)
Photographic films , but also the sensors of digital cameras (for example CCD ) are not only sensitive to the visible spectrum of light , but also to the invisible ultraviolet component. UV light can have two main disruptive effects when taking photos:
- Conventional camera lenses are only corrected for a certain range of visible light ; a high proportion of UV light can lead to blurring due to chromatic aberration ;
- If sunlight is scattered by the molecules of the air, the maximum intensity of the scattered light is in the UV range ( Rayleigh scattering ). This particularly "blue-heavy" scattered light (see picture) can cause a blue cast in color films .
The use of UV blocking filters effectively suppresses these effects, the photographs gain in contrast and sharpness, and color errors are avoided. A correction of the exposure settings is not necessary with UV blocking filters.
With modern cameras with multi-lens, coated lenses, the use of these filters is not necessary, as the overall thick glass of the lenses already blocks UV radiation sufficiently. If any other color filter or a polarization filter is used, an additional UV filter is superfluous and only reduces the imaging performance of the lens.
Many photographers see the main task of a UV blocking filter (similar to the skylight filter ) in protecting the lens from mechanical damage, especially scratches, as a filter is not only easier to replace than the front lens of a lens, but is also much cheaper. However, like all optical lens attachments, UV blocking filters have the disadvantage that they reflect light that is reflected from the front lens back into the lens and can thus lead to unsightly points of light in backlit images. Therefore, to protect the front lens lens hoods more appropriate.