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The Filter Factor



GUIDES & SUPPLEMENTS

TEXT BY Howard Millard

Sometimes the smallest and lightest accessory can make the most striking difference in the quality and impact of your photographs. I'm talking about filters. They're small, they're light, and they're relatively inexpensive. But they can really pack a wallop when it comes to dramatically altering and improving your photographs, in all kinds of weather and lighting conditions. In the last few years, new lines of physically thinner filters have appeared. This is most significant for polarizers, which tend to be thick. With a thick accessory, or a stack of two or more filters on your lens, vignetting, the darkening of the corners of the image can occur. The new thin filters help eliminate or minimize this effect. Vignetting may also be cured by combining two filters into one unit. One popular example of this is the melding of a warming filter and a polarizer (both are described below).

The Polarizer
A powerful tool for outdoor and architectural applications, polarizing filters make pictures look extraordinarily vibrant. They can control contrast, reduce reflections, and deepen blue skies using both color and black-and-white films, but only under certain conditions. For color, it can dramatically increase the richness of all colors and cut through haze with an optical razor's edge. Careful use of the polarizer can increase the impression of sharpness, remove or reduce glare, reveal unseen detail and bring the range of subject brightness more in line with the range your film can record.
However, since all this comes at the price of 1.5 to 2 f/stops of additional exposure, you may need to use a faster film or a tripod under less than ideal lighting conditions. For best results with today's autofocus, autoexposure cameras, you'll probably need a circular, rather than a linear, type of polarizer. With older manual cameras, the linear type is sufficient.
Mamiya America Corp. recently introduced the ZE702 PL (Polarizing) filter for its line of Mamiya 7II and Mamiya System lenses. The filter is designed to work in both manual and auto exposure modes without the need for exposure compensation. The filter shifts vertically from the shooting position in front of the lens without changing its polarization rotation to cover the small square window which contains the metering cell above the lens mount.
The polarization effect can be observed by looking directly through the filter over the top of the camera — not through the camera's rangefinder eyepiece. After determining the polarization effect and metering, the filter is returned to the down position in front of the lens.

THE DRAMATIC EFFECT OF THE COKIN STAR FILTER

Graduated Filters
When you're shooting a bright sky above a foreground in shade, a graduated ND (neutral density) filter can help lower the wide brightness range so that the film can record detail in both the highlights and the shadows. The top half of a graduated ND filter is a neutral gray, which feathers to clear in the center and bottom half of the filter. Some lower quality ND filters aren't pure gray and can add a color cast. Other graduated filters are intentionally colored to add blue or mauve to the sky.

Neutral Density Filters
ND filters are pure gray and reduce the amount of light striking the film theoretically without altering the color. These filters allow you to use slow shutter speeds in good light in order to create blurred motion effects for subjects like water falls and sports action.

Warming Filters
With designations like 81A, 81B, and 81C (in order of increasing strength), these yellowish filters are helpful to counter-balance the blue tint often encountered when photographing in shade or on overcast or rainy days, because they absorb ultraviolet and blue rays. They are also frequently used in sunlight or with flash to warm up skin tones and make a model look more tanned.

Diffusion Filters
Available in a variety of strengths, these filters soften the look of the subject and add a glow to portraits and landscapes. Since most diffusion filters reduce contrast significantly, you should use them in strong light, either sun or flash. Although they usually claim to require no compensation, I usually add an additional 1/2 stop of exposure for diffusion filters.
Caution: With some diffusion and fog filters, the effect may be reduced when you shoot at smaller apertures, like f/11 or f/16. If so, use wider apertures for the most pronounced results.
Some diffusion filters, such as Tiffen's Soft/FX series, have the uncanny ability to soften skin imperfections while still maintaining an appearance of sharpness, particularly in the eyes. Tiffen Soft/FX series filters have tiny, computer-designed lenslets arrayed within the glass. Precise areas of clear space between the lenslets keep the image looking sharp. The pattern of lenslets, can alter light throughout its surface, which creates the ability to soften unwanted details while keeping the image in focus.

Fog Filters
To add mystery to a landscape or cityscape, or for an old-world portrait or product look, try a fog filter. You'll see a softening of the subject overall, muted colors, lowered contrast, and often haloes surrounding bright areas. Like diffusers, fog filters come in several strengths and exposing at a smaller aperture reduces their effect.
The Mist Set by Lee Filters, offers a variety of fog effects. The set consists of a Graduated Mist, a Mist Stripe, and a Mist Clear Centre Spot. These filters can b used individually or in combinations to create varying densities of mist and fog.

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