A lot of photographers keep UV filters on their cameras almost all the time to protect their lenses. If you're one of those photographers, you should use a multicoated UV filter, which helps curb any additional image degradation, or flare, that you might otherwise get from the sun or reflective light sources. Multicoating can ensure that 99.7 percent of the available light gets into the camera -- that is, just about everything except for what you're deliberately trying to block [source: Sholik].
But even if you choose not to use a UV filter for lens protection, there are some situations in which you'll definitely want to attach one to improve or alter the quality of your images. Veteran photographers Stan Sholik and Ron Eggers recommend using a UV filter in certain environments, such as in the mountains or out in the ocean, where large amounts of UV radiation are found [source: Sholik]. Additionally, photographer Ross Hoddinott advises using a UV filter for aerial photography. You also can use a UV filter to boost the contrast when you're shooting outdoors in the shadows or on an overcast day. But you should be aware that UV filters won't reduce every type of atmospheric distortion -- they won't eliminate haziness resulting from mist or fog, for example.
Manufacturers offer various grades of UV filters, which enable you to choose one that best fits the conditions in which you're shooting. Tiffen, for example, offers a range: from a basic UV filter, which blocks only a minimal amount of UV radiation and is mostly intended for lens protection, to the Haze 2A, which absorbs virtually all UV [source: Tiffen].
Using a UV filter isn't very difficult. Usually, you just screw it onto your camera lens. If you're using a multicoated filter, you probably don't need to adjust your aperture or shutter speed to compensate, since the filter will reduce the amount of light by only a fraction of a percent [source: Hoddinott].