UV filters are mainly used to protect the lens from dust, scratches, and potential damage from accidental lens drops. They filter UV light that can cause a bluish haze in your photos, as regular film is sensitive not only to visible light but also to UV. They are useful when taking photos in mountains or at the sea or any other place with high UV light. They will filter the blue haze that usually blurs the background of your photo. They are also very useful when taking photos in the snow, as snow is an excellent UV reflector.