Camera filters are transparent or translucent optical elements that alter the properties of light entering the camera lens for the purpose of improving the image being recorded. Filters can affect contrast, sharpness, highlight flare, color, and light intensity, either individually, or in various combinations. They can also create a variety of "special effects." It is important to recognize that, even though there are many possibly confusing variations and applications, all filters behave a reasonably predictable way when their properties are understood and experienced. Most of these properties related similarly to filter use in both film and video imaging. The following will explain the basic optical characteristics of certain types of camera filters, as well as their applications. It is a foundation upon which to build by experience. Textual data cannot fully inform. There is always something new out there.
In their most successful applications, filter effects blend in with the rest of the image to help get the message across. Use caution when using a filter in a way that draws attention to itself as an effect. Combined with all the other elements of image-making, filters make visual statements, manipulate emotions and thought, and make believable what otherwise would not be. They get the viewer involved.
Filter effects can become a key part of the "look" of a production, if considered in the planning stages. They can also provide a crucial last-minute fix to unexpected problems, if you have them readily available. Where possible, it is best to run advance tests for pre-conceived situations when time allows.