The most common filter used in photography is designed simply for protection. There are three kinds of protective filters on the market-- UV, skylight and haze.

While there are small differences between the UV, skylight and haze filters, their main purpose is the same-- protecting the investment in your lens. In essence, these filters are a clear piece of glass designed to cover the front element of your lens, acting as a shield against the dangers of the outside world.

As you clean your lens over time, you may damage the glass and coatings. While dirt particles and other contaminants can certainly scratch the glass itself during the cleaning process, the lens coatings are even more fragile and susceptible to damage.

Lens manufacturers put coatings on the lens to control reflected light so the camera can gather more color and light information for better images. Often, the coatings are actually evaporated onto the lens which means that it does not take a lot to damage them.

By placing a filter on the lens, the lens always remains free of dirt and contaminants. While the filter will need to be cleaned and, eventually, replaced; it is easier and cheaper to get a $20 filter than it is to replace a $400 lens.

In addition, these filters can protect your lens against impact damage and other mishaps. Filters are designed to absorb the force of an impact to protect the lens in much the same way a car is designed with crumple zones to protect the occupants in a crash. If you bump up against something or drop your camera, the filter ring will bend and the glass in the filter will break. Often, this is enough impact absorption to save the lens and camera.

Functionally, UV, skylight and haze filters share more in common than not. However, there are several minute differences between them.

The most important of these differences is the color of the filter. UV filters will eliminate some of the blue tones inherent in UV light as a result of the way they process the light rays, but the filter itself is clear. Skylight filters have a mild pink cast which has a slightly greater warming effect than a UV filter. Finally, haze filters have a yellow cast which tends to cancel the blue tones produced by UV light.