Perhaps the single greatest thing about optical filters—those transparent, usually round, usually glass light modifiers that screw onto your lens—is that they allow you to add creative effects easily at the moment of exposure.
In this day and age when you can apply a very realistic filter effect to an image in Photoshop (or, sometimes, even using in-camera software), is there still a need for optical filters? You bet! Applying filter effects can be time-consuming, while adding a filter in the field means you can capture the image you want, right in camera. You can see a filter's effects instantly by simply mounting the filter and looking through your SLR's optical viewfinder, or through the electronic viewfinder of an EVF camera or MILC.
Also read: Filter FAQ at the Adorama Learning Center
Adorama carries literally thousands of Optical filters, which you can find in the Camera Lens Filters, Video Filters and Accessories department. Optical filters can affect photos in very subtle to extreme ways. There are color balancing filters, diffusion filters, polarizing filters, and an endless variety of special effects filters. There is even one very useful filter—the UV protective filter--that has little visual effect--it just protects the front elements of your lens.
Yes, you can emulate some of the effects provided by many optical filters by using Photoshop-compatible plug-in-filters after you've taken the picture. But software filters can't emulate every optical filter. The effect of polarizers in controlling light rays cannot be duplicated in software--and software certainly can't protect your lens's valuable front element.
Polarizing filters: Enhanced color plus reflection control
Often described as the single most useful optical filter, a polarizer is a variable-control filter that lets you eliminate or minimize glare on many surfaces (e.g. water or glass, but not metal) by simply turning its front ring and observing the effect in the viewfinder. Browse Adorama's Polarizing Filters department.
Polarizing filters: Positives and negatives:
* Eliminates glare on glass surfaces
* Deepens blue skies
* Saturates vegetation color
* Slight loss of brightness
It works by selectively transmitting or blocking light waves depending on their direction of vibration. With a polarizer, you can eliminate the reflections in a store window and shoot a clear picture of the display behind the glass, or eliminate reflections on the water, revealing any fish swimming just below the surface.
More important, you can often achieve dramatic effects by enhancing the contrast of clouds against sky, or increasing the saturation (richness) of the colors in a landscape--all by turning the polarizer's front ring until you see the effect you want.
Circular vs. linear polarizers
Polarizing filters come in two main types, linear and circular. The linear type works fine with manual cameras, but may produce erroneous exposure readings with cameras that feature through-the-lens metering. Linear polarizers may also adversely affect the performance of some autofocus systems. Unless you have a manual-everything camera, get a circular polarizer--it works properly with all camera systems.
Polarizing filter rule of thumb
If you want to determine the area of sky that's most effectively polarized with a circular polarizer, point your index finger at the sun with your thumb extended at a right angle (90 degrees) to your index finger. While keeping your finger pointed at the sun, rotate your thumb around the axis of your index finger. The arc indicated by your thumb will point out the band of deepest blue from horizon to horizon.
Reflections be gone: Polarizers can be adjusted to reduce or eliminate reflections on glass, something Photoshop can't do. Photos by Mason Resnick.
Protective filters: First line of defense
Many photographers use UV protector or clear glass filters to protect camera or camcorder lenses against dust, moisture, fingerprints and other damage. They can be kept on your camera at all times because they have virtually no effect in ordinary picture taking, but will absorb ultraviolet radiation that's invisible to your eyes. UV may shows up as a slight bluish cast in images taken at high altitudes or over water, especially with film or video cameras.
Other filters used as lens protectors include the very light pinkish Skylight 1A, which adds a touch of warmth, or the Haze filter (available in different strengths) that absorbs more UV than a UV protector filter. Incidentally, none of these protective filters will adversely affect picture sharpness so long as they are high-quality filters made by reputable manufacturers.
Browse Protective UV & Skylight filters at Adorama.
Special-effects filters: Hollywood at your fingertips
These include an incredible variety of starburst and prismatic effects as well as soft focus filters ranging from slightly soft to very soft to variably soft (sharp in the center and increasingly soft toward the edges of the frame). There are textured, partially textured, and partially clear filters that give unique fog, mist, and diffusion effects, and even variable-color filters that change slowly from, say, red to blue as you turn the front ring, giving you an infinite range of in-between hues.
Seeing stars: The star effect filter is a simple tool that adds a cross-star to the specular highlights of your photos. Mandy Mullin saw this sunset and placed a Star Effect filter over his 18-55mm kit lens that he was using with his Canon EOS Digital Rebel XT. He turned the filter until the star lines were just right. Exposure, 1/200 second at f/5.6, ISO setting, 100. Photo © Mandy Mullin.
While some special-effects filters will only be used occasionally, they're great to have in your gadget bag when you want to shoot that special soft-focus romantic portrait or add a bit of starburst sparkle to a photo of a holiday display. Their prime attributes are simplicity and predictability--just screw them onto your lens and you know what effect you're going to get.
Browse Special Effect and Image Softening filters.
Go soft: To get capture ethereal glow in this still life with pear and grapes, photographer William Myers used a Tiffen SoftFX5 filter. Exposure, under window illumination: 7 seconds at f/16 with a Nikon D100 camera, unspecified lens. Photo © William Myers.
Graduated filters: A degree of expert image control
These filters are not uniform in color or tone, but of variable density (light transmission ability) over their surface. Their greatest asset is that they let you reduce the brightness ratio of a contrasty scene where your camera's image sensor (or film) cannot capture the brightest and darkest areas in a single exposure. It works by reducing the exposure in the brightest parts of the scene, while allowing full exposure in the darkest areas.
Graduated color filters allow you to add color selectively, while leaving the rest of the scene unaffected--for example perking up a warm sunrise sky without affecting the colors in the foreground.
Smokin' tobacco: Is this overuse of a filter, or just right? Often to use or not to use a filter is a matter of personal taste. To get this otherworldly effect in his photo of Stonehenge, Chee-Onn Leong used a tobacco-colored graduated filter along with a polarizer. The photo was captured with a Canon EOS 5 and 28-80mm lens on Fuji Velvia 50 film. Photo © Chee-Onn Leong.
Browse Graduated Filters at Adorama.
Neutral graduated filters are most often used to capture detail in a bright sky by reducing the exposure without affecting color accuracy. Graduated filters are available in different densities, and typically the transition from the maximum density area to the clear portion is gradual, giving a natural-looking effect rather than an abrupt transition.
Subtle effect: To achieve a rich colored sky in this dramatic sunset photo over a tidepool, Marc Adamus used a 3-stop Hard ND Graduated filter. Without this filter, the sky would have been too bright. Adamus carefully positioned the filter so the transition from clear to gray fell on the horizon line, so a casual viewer couldn't tell he used this filter. The photo was made with an unspecified Canon EOS SLR and Canon wide-angle zoom lens on Fujichrome Velvia 50. Photo © Marc Adamus.
Black-and-white contrast filters: Vintage effect made simple
How did Ansel Adams get those dramatic, almost-black skies against puffy white clouds? He used color filters when shooting his classic black-and-white shots. The medium yellow filter is great for enhanced cloud effects, while red filters produce dramatic dark skies a la Ansel. Light green is good for pleasing skin tones in portraits, and blue accentuates haze and fog. Of course the entire black-and-white filter range is still available brand new, and they're great for getting that retro look into your black-and-white images.
If you have a collection of old black-and-white filters, the good news is that you can still use them for black-and-white digital imaging. Just set your digital SLR to black-and-white mode screw the filter onto your lens, and start experimenting (unlike film photography, black-and-white digital cameras let you see and analyze your photos as soon as you've shot them.)
Browse Black & White Contrast filters at Adorama.
Color-conversion filters: For film shooters only
These filters are designed primarily for film cameras because digital cameras provide white balance controls for shooting under daylight-, tungsten-balanced (household lamps), or mixed illumination, and sophisticated digital cameras offer manual white balance control. But if you're shooting film, especially slide film, these filters are still very useful. Most popular are the 80A filter, that allows you to shoot daylight film with most standard tungsten lighting, the 80B filter which lets you do the same with photofloods, and the 85 and 85B which lets you shoot tungsten-balanced film in daylight.
Browse Color conversion filters at Adorama.
Fluorescent filters: Eliminate the "green meanies"
While most digital cameras do a reasonably good job of delivering natural-looking colors under the fluorescent lights often encountered in kitchens, office spaces, commercial buildings and factories, pictures taken under common cool white fluorescent lights (rather than more expensive daylight-balanced fluorescents) may still have a greenish cast that's especially noticeable in skin tones. If you do a lot of digital shooting under such conditions (or you use daylight-balanced slide film), try a daylight fluorescent filter, which looks magenta and often gives more natural-looking skin tones. Make sure to set your digital camera's white balance to daylight setting when using it.
Neutral density filters: You want less light?
As their name implies, neutral density filters add density--that is, they block some of the light entering the lens. They look gray to the eye and have little, if any, effect on the color balance of a photo. Why would you want to reduce the light striking the image sensor or film? It can be very useful when shooting in brilliant sunshine and you want to set a wide aperture to blur a distracting background, or a slow shutter speed to deliberately blur a moving subject, such as a waterfall. Neutral density filters come in various strengths to reduce the amount of light by less than one f/stop to as many as 10 full stops. Browse Neutral Density filters at Adorama.