You can do a lot in postprocessing with a digital image, and many digital cameras have built-in filters, but there's still a good case to be made for using some on-lens filters for black-and-white photography.
Some effects can't be simulated in postprocessing. For example, a polarizer can reduce or eliminate reflections from nonmetallic surfaces (water, glass and the like), as well as reduce the effects of atmospheric haze to improve contrast. A neutral-density filter can let you shoot at water-blurring shutter speeds even in bright light, for another. Tips: If you intend to use the camera's built-in metering or AF system, use a circular polarizer rather than a less costly linear one. The latter will interfere with metering and AF operation. A set of ND filters in various strengths can be costly; a better choice for black-and-white work is a variable ND filter, which lets you adjust the strength, as needed (variable ND filters can cause color shifts as their strength is increased, but that's not an issue in black-and-white).
Black-and-white shooters have long used colored filters to control tonal rendition in their images. A colored filter transmits light of its own and similar colors, while blocking light of complementary color. Thus, a yellow or red filter can be used to darken a blue sky in a landscape shot so white cloud buildups stand out dramatically. Colored filters can also be used to provide separation between objects in a scene that would appear as about the same shade of gray without the filter. For example, red flowers and green leaves reflect about the same amount of light, so both appear about the same shade of gray in a black-and-white photo. Shoot through a red filter, and the red flowers appear lighter while the green leaves appear darker; conversely, a green filter will "lighten" the green leaves while "darkening" the red flowers.
Graduated ND filters can be used to reduce the brightness of the sky in a landscape so you can record detail in both sky and shaded foreground with a single exposure. HDR techniques mean digital photographers have less need for grad ND filters than film shooters, but they're still useful accessories.
A number of manufacturers offer photographic filters. Here's a look at some of the most popular:
Founded in 1947 in Berlin by Herrs Biermann and Weber, B+W merged with Jos. Schneider Optical Works of Bad Kreuznach, Germany, in 1985. B+W's MRC multi-coatings were the first water- and dust-repellent coatings. B+W offers circular polarizers (including Kaesemann ones that transmit more light than conventional polarizers), neutral-density filters from 0.3-3.0, plus the five-stop XS-Pro Digital ND Vario MRC nano, graduated ND and colored filters (yellow, orange and red) for black-and-white photography. They're screw-in glass filters with brass mounting rings in sizes from 37mm-122mm. www.schneideroptics.com
The French Cokin company offers a wide line of rectangular filters that slip into the Cokin filter holder (available in four sizes), which can be attached to lenses with diameters from 36mm to 112mm via adapter rings—you buy a holder, the desired filters and adapter rings to fit each of your different-diameter lenses. Cokin offers gray (ND), graduated gray, circular polarizing and colored filters among their wide variety. They also offer very thin Pure Harmonie circular filters, among them a circular polarizer and a 2- to 8-stop variable ND. www.cokin-filters.com
German filter manufacturer Heliopan, founded in 1949, offers a wide range of quality filters made of Schott glass mounted in brass rings. These include circular polarizers, NDs from 0.3-3.0 (some special order), vario gray that provides strengths from 0.3-1.8 (1-6 stops), graduated NDs and colored filters (yellow, orange and red). www.macgroupus.com
Hoya offers a complete line of pro-grade filters, including their new HD3 series, which are specially designed for durability in extreme environments. Four times stronger than typical optical glass, and featuring a new 32-layer coating to eliminate reflections with a 99.7% light transmission rate, these filters are water repellant and highly stain and scratch resistant, making them ideally suited for outdoor use. Hoya's HD3 filters are currently available in UV and Circular Polarizer models. www.kenkotokinausa.com
The Japanese Kenko company offers circular polarizers, and neutral-density and variable-ND filters made of optical glass. The Zeta EX Circular Polarizer is the world's thinnest and lightest circular polarizer. The Variable NDX delivers densities from 2.5X-1000X (practical maximum 450X), or 1.5-8.5 stops (beyond 450X, polarization problems render images unusable with all variable ND filters). A depolarization plate minimizes color shifts at higher strengths. www.kenkotokinausa.com
LEE Seven5 Filter System
LEE Filters offers a system featuring holders in three sizes, adapter rings and a variety of filters, both acrylic and glass. The Seven5 holder is for compact-system cameras (mirrorless), and takes 75mm filters and adapters from 37mm-72mm. The 100mm holder takes 100mm filters and adapter rings from 49mm-105mm. The SW 150 holder takes 150mm filters and is for superwide-angle lenses. Filters include the ProGlass ND in 0.6 and 0.9 strengths, Big Stopper (10-stop ND), Little Stopper (6-stop ND) and Landscape Polariser (large-diameter thin filter that can be used with 15mm-17mm lenses on a full-frame sensor), plus many others. Each filter is handmade and individually inspected before it leaves the factory. www.leefilters.com
For more than 60 years, Marumi has been making camera filters in Japan, introducing Digital High Grade filters in the early days of digital. Marumi offers circular polarizers, neutral-density filters (including a 100000X one for photographing solar eclipses) and a nine-stop VariND filter. The Exus line features the best quality, followed by the Super DHG line, the DHG line and the Fit & Slim line—Marumi offers something for every photographer. www.argraph.com
Pro-Optic offers value-priced digital multi-coated CPL circular polarizers in sizes from 52mm-77mm, and Variable HD ND filters (ND2-ND400) in 72mm and 77mm sizes. www.adorama.com
Singh-Ray offers high-end filters, including some unique ones. The Mor-Slo Solid Neutral Density Filters (glass) come in 5-, 10-, 15- and 20-stop strengths, while the George Lepp (a familiar name here at OP ) Solid Neutral Density Filters (optical resin) come in 1-, 2-, 3- and 4-stop strengths. The Vari-ND Circular Variable Neutral Density Filter (glass) provides from 2-8 stops of light reduction. The Galen Rowell (another familiar name to longtime OP readers) Graduated ND Filters (optic resin) come in hard- and soft-edged versions in 1-, 2-, 3- and 4-stop strengths. The Gold-N-Blue Polarizer can enhance contrast in black-and-white images of scenes containing those colors. www.singh-ray.com
New York-based Tiffen has been making filters for the motion-picture industry, as well as pro and other still photographers, for more than 75 years, and has been recognized by the Academy of Motion Picture Arts and Sciences and the Academy of Television Arts & Sciences for technical achievements. Tiffen offers high-quality circular polarizers, ND filters (0.3, 0.6 and 0.9 strengths) and colored filters (yellow, deep yellow, red, green and blue) that work well for black-and-white as well as color photography. tiffen.com