Photographic filter
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In photography and cinematography, a filter is a camera accessory consisting of an optical filter that can be inserted into the optical path. The filter can be of a square or oblong shape and mounted
Four photographic filters (clockwise from top-left): an infrared hot mirror filter, a polarizing filter, and a UV filter. The larger filter is a polarizer for Cokin-style filter mounts.
Markings on Hoya multicoated skylight filter, identifying size and equivalent Wratten number (1A)
An extreme case: a Nikon D700 with a smashed filter which may have saved the Nikkor lens beneath. Usually, all that can reasonably be expected is protection from scratches, nicks and airborne contaminants.
Infrared filters
Wratten number
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Wratten numbers are a labeling system for optical filters, usually for photographic use comprising a number sometimes followed by a letter. The number denotes the color of the filter and its spectral
Photographic filter
…be necessary to avoid vignetting when using wide-angle lenses. There is no universal or reliably standard naming or labelling system for filters. The Wratten numbers adopted in the early twentieth century by Kodak, then a dominant force in film photography, are used by several manufacturers, including B+W, but the…
Kodak Wratten filter 80A in its original packaging