Buyer's Guide 2007: Digital Camera Accessories Matter!
The right selection of gear will make shooting easier and more successful
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.