A UV filter is a clear glass filter that attaches to the front of the lens. Its primary function is to block ultraviolet radiation, which is invisible to the human eye but can be detected by a camera’s sensor. Under specific conditions—such as in high mountains or by the sea—this radiation can cause a slight bluish tint and a slight reduction in contrast in photographs. The filter reduces this effect, contributing to a cleaner and sharper image. In modern digital photography, however, its second function is more commonly used: as permanent mechanical protection for the front lens element. It protects the expensive lens element from scratches, dust, moisture, and fingerprints, and replacing the filter is significantly cheaper than repairing the lens.