UV is annoyingly present when doing landscapes and aerial photography. It records as a haze that blocks the clear view of distant mountains and it veils the land when imaged from high altitudes. A UV blocking filter can be very helpful under these circumstances. The UV filter and a cousin called a “Skylight” filter gained popularity. The “skylight” is tinted pink, so this UV filter also warmed up cool feeling blue-sky type vistas. Special note: The UV filter only benefits when the subject is distant and shrouded by water vapor. Camera store salesmen, eager to pad a sale, generally advised, a UV filter will protect your precious, costly lens. The popularity of the UV thus soared.

With the onset of the digital camera, the need to mount a UV filter diminished because electronic photography raises different issues. The imaging sensor requires trimming with filters or it will fail to deliver a faithful image. The surface of the digital sensor is covered with an array of tiny photosites. These capture the image, but the chances that artifacts with spoil it are high. Most noteworthy is image noise. This is akin to grain in film photography. There are a plethora of these annoying artifacts.

Enter the digital camera’s protective cover glass. The surface of the digital image sensor is fragile, it is covered by a flat glass overlay. This cover glass lends itself to have a dual purpose. Some subject types will image with bizarre results. These are called “demosaicing artifacts, often seen as a moiré. To avoid, the cover glass is also a optical low-pass filter better known as a anti-aliasing filter. This filter slightly blurs fine detail that is finer than the native resolution of the senor. Additionally the cover glass will act as an infrared filter that blocks these frequencies otherwise they will record as false colors

The UV continues to be sold and mounted to protect our precious lenses.