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Toolbox: Must-Have Optical Filters

Even the best software can't replace them

This Article Features Photo Zoom

Heliopan 4x Graduated ND

High-quality filters also have coatings to protect the filter's surface, improve light transmission by reducing reflections and preserve color fidelity. Filter thickness is another consideration—too-thick filters will cause vignetting with wide-angle lenses. Low-profile filters are available for the most common models, and these are your best options to reduce the possibility of vignetting.

THE CIRCULAR POLARIZER
The number-one must-have filter for every photographer is the circular polarizer because its effects truly can't be replicated with software. Polarizers eliminate surface glares and reflections. This is important because glare will completely blow out details that can't be re-created after the fact—once you lose highlight details in the exposure, they're gone forever. A polarizer improves color saturation, too. They're also useful for capturing more dramatic skies, especially when there are prominent clouds. Blues are more vibrant, and the subtle details on the clouds are brought out.

B+W UV Haze

THE NEUTRAL-DENSITY FILTER
When a scene is too bright for the exposure you'd like to make, a neutral-density filter is indispensable. For example, you may want to use a long shutter speed to blur moving water, but because the scene is too bright, you'd be left with a serious overexposure. ND filters solve this problem by reducing the amount of light that reaches your sensor. The most common ND densities are 2x, 4x and 8x. A 2x allows half of the light through for a one-stop exposure increase; a 4x cuts the light to one-quarter for a two-stop exposure increase; and the 8x cuts all but one-eighth of the light for a three-stop exposure increase.

Tiffen 25a Red For B&W

THE GRADUATED NEUTRAL-DENSITY FILTER
Sometimes you don't want to reduce the total light in a scene, just part of it. Graduated ND filters are particularly helpful when trying to reconcile a very high-contrast scene—think of a sky lit up at sunset, with a much darker foreground. These two areas of your composition require different exposures: shorter for the sky and longer for the foreground. A graduated ND is perfectly clear at one edge and transitions to dark on the opposite edge. Position the dark half over the brighter area of the scene to lessen exposure disparity. Like ND filters, graduated ND filters are available in different densities.

THE UV FILTER
Designed to eliminate the ultraviolet spectrum, many photographers swear by these (or skylight filters, which remove excess blue), not for their photographic effect, but as protection for their lenses. The argument against this is that any glass in front of your lens will alter the image, even if very subtly. However, dust inevitably will collect on your lens—would you rather clean a filter or your front lens element? Using a filter in this way also protects it from dings and scratches. If you know you'll be working in a potentially harsh environment, like the beach on a windy day, it's good to know you have a filter handy that can help protect your lens with minimal effect on the image.

FILTERS FOR B&W
The black-and-white masters made use of several colored filters to enhance or reduce contrast in a photograph. Yellow, orange and red are the most useful for their ability to darken skies and enhance detail in clouds. Yellow has the least effect, and red will have the most. Colored filters work by allowing their color to pass through while filtering out the opposite color as seen on a color wheel. Red is opposite cyan, which is why a red filter will make a cyan sky look dark gray or even black. The caveat with these filters is that you need to know ahead of time that you want to make a black-and-white image. We suggest setting manual white balance, then mounting the filter, checking the exposure and shooting in a full color mode (instead of the monochrome mode). Then do your conversion to black-and-white in software after the fact. The monochrome shooting mode is convenient for checking the effect as you shoot, but you'll preserve the maximum image quality by taking your "keeper" shot in the color mode.

SPECIAL-EFFECTS FILTERS
There are all sorts of wacky effects filters that do everything from fuzzing the edges out to creating a kaleidoscope effect. These can be fun to experiment with, but beware of overdoing it. Sometimes simpler is better, and it's easy to get carried away.

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