Tuesday, September 3, 2013
Gadget Bag: The Fall Color Filter
For cutting glare and getting natural saturated reds, yellows and oranges, the polarizer is your autumn companion
The polarizer works its magic especially well on fall colors. Rotated to the proper angle, the filter can bring out those rich colors by eliminating the polarized reflections that desaturate them. It can deepen the blue of the sky and penetrate atmospheric haze (but not solid particulate matter like dust or water droplets), increasing contrast by eliminating polarized rays. The polarizer also can reduce or eliminate polarized reflections from nonmetallic surfaces like water.
Wait a minute, a polarizing filter eliminates polarized light? Doesn't it polarize light? Both. The polarizer polarizes normal non-polarized rays, and can, when rotated appropriately, block polarized rays. Normal light waves vibrate in all directions perpendicular to their path of travel. A polarizer allows waves vibrating in only one direction to pass, blocking all other waves. You can control it by rotating the filter. When light is polarized—the waves vibrating in just one direction—the polarizer can block it when you rotate the filter appropriately.
It's easy to use a polarizer. Just attach it to your camera's lens and watch through the viewfinder while you rotate the filter. You can see the effect change as you rotate the filter. For sky-darkening, bear in mind that the effect will be strongest at a 90° angle to the sun (i.e., when the sun is to one side, rather than when shooting with the sun behind you, or into the sun). And since the effect varies depending on the angle from the sun, you can get uneven skies when working with a wide-angle lens. For saturating colorful autumn leaves, just rotate the filter until you see an effect you like.
If your camera doesn't offer TTL viewing, just hold the filter up to your eye, rotate it until you see the effect you want, then attach it to the lens in that orientation.
Polarizers have filter factors from around 1.3 stops to 3 stops, depending on the filter and lighting conditions. It's a good idea to bracket exposures when using a polarizer, and be aware that some polarizers produce a slight cool cast. You can get a combination polarizer-warming filter to counter this.
Introduced by photographer Jean Coquin some 35 years ago, the Cokin Creative Filter System comprises rectangular filters that fit into a special holder that attaches to the lens via an interchangeable metal ring. You can use the same filter and holder on lenses with different diameters simply by changing the ring—a big money-saver if you have a large, varied lens collection. Polarizers are available in circular (164) and linear (160) form—just two of more than 160 filters in the system—in all four Cokin system sizes: small, medium, large and extra-large. Cokin also offers the PURE Harmonie series, featuring a superthin 4.5mm circular polarizer with a factor of just one stop, available in circular sizes from 37mm to 82mm. www.cokin-filters.com
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