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Page 3 of 4
Filters
One of the most popular filters is the polarizer because it works for
both color and black-and-white photography and serves several handy
functions. It can eliminate glare and reflections from nonmetallic
surfaces, darken a blue sky so that white clouds really stand out, cut
through atmospheric haze and serve as a 2.5x neutral-density filter.
Polarizers are most effective when used at certain angles relative to
the light source and subject. They’re simple to use: Just hold the
filter in front of an eye and rotate it (the filter, not your eye), and
you can see exactly what it does for any given scene. If your camera
provides TTL viewing, you can attach the filter to the lens and check
the effect through the viewfinder.
The metering and AF systems
in D-SLRs require use of a special circular polarizer, which is a bit
more expensive than a standard linear polarizer, but worth the extra
cost if you wish to retain TTL metering and AF functions. If you must
use a linear polarizer, focus and meter without the filter, increase
the exposure by 1.3 stops to compensate for light blocked by the
filter, then mount the filter over the lens and take the shot.
Neutral-density (ND) filters reduce the amount of light entering the
lens without otherwise changing it. They’re handy when you want to do
selective-focus or long-exposure blur effects in bright light. ND
filters come in a variety of strengths. Singh-Ray’s Vari-ND provides
densities from two to eight stops in a single filter.
Graduated neutral-density filters are popular with landscape
photographers. Grads are half clear and half dense, the idea being you
can position the filter so the clear half lets all the light through
from a dark foreground, while the dense half blocks some of the light
from the bright sky, thus enabling you to record detail in both areas.
Graduated filters also come in colors to add special enhancements to
your images. For example, an orange graduated filter can add color as
well as density to a sunset sky, while a blue graduated filter can add
density and color to a “bald” midday sky.
Colored filters are
popular with black-and-white photographers. Most digital cameras that
have a black-and-white mode also have some colored filter effects built
in. If yours doesn’t, a red number 25 filter will really darken a blue
sky, making white clouds stand out dramatically. Colored filters
lighten objects in the scene of their own and similar colors and darken
objects of complementary color. For example, the red filter can also be
used to provide contrast between red flowers and green leaves in a
black-and-white shot of a rosebush.
UV and haze filters don’t
really affect digital images, but if you shoot in harsh shooting
environments, they can be used to protect your lens from damage. It’s
better if wind-blown sand particles and water spray hit the filter
rather than your lens’ front element.
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Buyer's Guides 
