Filters

Filters used for photographic purposes are camera accessories that consist of an optical film which can be inserted in the optical path. These filters are screwed in front of the camera lens. They allow the photographer to better control the images that are produced. In some cases, filters are used to make subtle changes to the images; sometimes, it is not possible to take the image without the appropriate use of the filters. The Wratten number is used to identify the number of filters. Filters for camera lenses are usually circular in shape and encased in metal or plastic ring frames. Though less common, filters in rectangular or square shapes are also available. They are mounted in a holder accessory.

Photographic or camera filters can be classified according to their intended use. The different types of filters (classified according to their use) are clear and ultraviolet, colour correction, colour subtraction, contrast enhancement, infrared, neutral density (graduated ND, solar filter), special effects (graduated colour, cross screen, diffusion, sepia tone, spot, close-up) and polarising filters. Clear and ultraviolet filters are transparent. Though, technically, they are not filters, they are generally used to protect the front of the lens. Polarising filters are used in both colour as well as black and white photography. These kinds so filters can be used to darken overly light skies as well as to increase colour saturation. Polarising filters are often used while dealing with situations involving reflecting surfaces like water and glass.