Even the most sophisticated camera can't adjust to the nuances of light like the human eye and brain can. That's why it's such a shock when a photo image looks completely different from the image you've retained in your mind. Why does that finely-chiseled backdrop of mountains you admired with your eyes disappear into the off-white haze of the horizon in your photo?
The culprit is UV radiation, which is outside the range of visible light but still can affect photographic images by lowering their overall contrast. Don't despair. You can overcome the problem by using a UV filter. By reducing the amount of UV light, you can capture a photographic image that more closely resembles the image in the light table of your mind. If you're artistically minded, you can use a filter to subtly convey emotion, evoke memories and summon up other feelings that embellish and shape the way we see the world [sources: Sholik, Hoddinott].
When you look through a UV filter, the thin, clear piece of glass inside a plastic or metal ring doesn't seem to block any light at all. That's because you can't see UV, the sort of light that it filters, which has a shorter wavelength than visible light. The filtering occurs at the subatomic level. The particular arrangement of electrons in the atoms that make up the filter allows most frequencies of light to get through. But it hinders part of the UV range, which includes everything below 400 nanometers in wavelength [source: Chemistry Department, Michigan State University].
Some photography blogs and manuals argue that UV filtering isn't really needed as much as it once was, because of advances in both film and digital imaging. But UV filters also perform another valuable function. Because you can leave them on your camera pretty much all of the time, the filter protects your lens from being contaminated with dust or scratched while you're out on a shoot. Unlike a camera lens, which can cost hundreds of dollars, you can buy a UV filter for $20 or less, so it's much more expendable -- though, with a little care, it's fairly durable, as well [source: Hoddinott].
In this article, we'll discuss how UV filters work and which different varieties of UV filters are available, and we'll also give you some tips on how to use them and take care of them.
How to Use UV Filters on Your Lens
A lot of photographers keep UV filters on their cameras almost all the time to protect their lenses. If you're one of those photographers, you should use a multicoated UV filter, which helps curb any additional image degradation, or flare, that you might otherwise get from the sun or reflective light sources. Multicoating can ensure that 99.7 percent of the available light gets into the camera -- that is, just about everything except for what you're deliberately trying to block [source: Sholik].
But even if you choose not to use a UV filter for lens protection, there are some situations in which you'll definitely want to attach one to improve or alter the quality of your images. Veteran photographers Stan Sholik and Ron Eggers recommend using a UV filter in certain environments, such as in the mountains or out in the ocean, where large amounts of UV radiation are found [source: Sholik]. Additionally, photographer Ross Hoddinott advises using a UV filter for aerial photography. You also can use a UV filter to boost the contrast when you're shooting outdoors in the shadows or on an overcast day. But you should be aware that UV filters won't reduce every type of atmospheric distortion -- they won't eliminate haziness resulting from mist or fog, for example.
Manufacturers offer various grades of UV filters, which enable you to choose one that best fits the conditions in which you're shooting. Tiffen, for example, offers a range: from a basic UV filter, which blocks only a minimal amount of UV radiation and is mostly intended for lens protection, to the Haze 2A, which absorbs virtually all UV [source: Tiffen].
Using a UV filter isn't very difficult. Usually, you just screw it onto your camera lens. If you're using a multicoated filter, you probably don't need to adjust your aperture or shutter speed to compensate, since the filter will reduce the amount of light by only a fraction of a percent [source: Hoddinott].
How to Clean UV Lens Filters
You should clean your UV filter about as often as you would clean a camera lens -- not very often. Both filters and lenses can accumulate quite a bit of dirt before the imaging ability will be significantly degraded, and you're likely to inflict more damage with smudge marks from cleaning. Optical glass, while harder than most metals, is softer than sand and the silicate materials that make up most of the Earth's crust, so if you rub a tad too hard, you're likely to scratch your filter or lens. Instead, blow or gently brush dust off the optical glass.
If your UV filter does get really dirty, or it accumulates a residue of something like sea spray or an oily fingerprint that won't come off with blowing or brushing, then do what you must. Some camera manufacturers make special cleaning devices, such as Nikon's Lens Pen, which combines a brush and a microfiber pad for lifting greasy marks from optical glass. Zeiss and other companies also market special lens cleaning solutions that can also be used on filters. If you're going to use a cleaning solution, administer it with a special soft lens cloth, which itself should be washed between each use [source: Atkins].
For more information on photography dos and don'ts, visit the links on the next page.
- "Camera Lens Filters." Cambridgeincolour.com. (Jan. 3, 2011) http://www.cambridgeincolour.com/tutorials/camera-lens-filters.htm
- "Filters for Color and Black & White Imaging." Tiffen.com. (Jan. 3, 2011)http://www.tiffen.com/filters.htm?CID=exit&idhbx=tiffen-filters
- Hoddinott, Ross. "The Digital Photographer's Guide to Filters: The Complete Guide to Hardware and Software Filtration." David & Charles. 2007. (Jan. 3, 2011.) http://books.google.com/books?id=Dn3O0yhsW70C&printsec=frontcover#v=onepage&q&f=false
- "Photographic lens and filter cleaning." Bob Atkins Photography. (Jan. 3, 2011) http://www.bobatkins.com/photography/tutorials/lens_filter_cleaning.html
- Sholik, Stan and Eggers, Ron. "Photographer's Filter Handbook: A Complete Guide to Selection and Use." Amherst Media. 2002. (Jan. 3, 2011) http://books.google.com/books?id=zCjUxrFvAcQC&printsec=frontcover#v=onepage&q=UV%20filter&f=false
- "Visible and Ultraviolet Spectroscopy." Chemistry Department, Michigan State University. (Jan. 3, 2011) http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htm