UV or clear glass filter placed over the front element to protect against dust, scratches, and moisture — optically neutral.
Technical Details
Multi-coated protection filters reduce reflections to below 0.5% per surface, compared to 4% for uncoated filters. High-quality filters use Schott B270 crown glass or equivalent optical glass with planarity under 30 arcseconds. Slim versions with 3-5mm frames prevent vignetting on wide-angle lenses from 24mm focal length. Waterproof filters conforming to IPX7 standard can withstand 30 minutes submerged at a depth of one meter.
History & Development
Kodak introduced the first mass-produced UV filters as protection filters for 16mm Bolex cameras in 1954. Tiffen established multi-coating technology for film productions in 1961, after NASA requirements had led to the development of corresponding coatings for space missions. Digital cameras since 2005 no longer require UV filtration, as CCD and CMOS sensors already integrate UV-blocking filters. B+W introduced nano-coatings in 2010, which facilitate cleaning by 60%.
Practical Use in Film
Emmanuel Lubezki deliberately omitted protection filters for "The Revenant" (2015) to ensure maximum sharpness, but replaced damaged front elements of three Zeiss Master Primes for $18,000. Underwater shots in "Life of Pi" (2012) utilized waterproof protection filters in front of $150,000 Panavision optics. VFX-heavy productions prefer filter-free shooting, as additional glass surfaces can amplify lens flares and ghosting artifacts. Location shoots in dusty environments – such as "Mad Max: Fury Road" (2015) – fundamentally employ protection filters, as lens repairs cost shooting days.
Comparison & Alternatives
Protection filters differ from ND (Neutral Density) filters by not reducing light and from polarizing filters by having constant transmission. Lens hoods offer mechanical protection without an additional glass surface, but do not protect against frontal impacts. UV filters reduce haze in analog film recordings, while clear filters serve exclusively a protective function. Modern nano-coatings are increasingly replacing classic multi-coatings, as they reduce dirt adhesion by up to 80% and minimize cleaning effort.