Monday, May 7, 2007

May 7, 2007 HelpLine

DPMag Published in HelpLine

Q) I know you've answered this in the past, I but can't seem to find my issue. I want to get a polarizer for my camera. Which type should I get?

Lou K., Santa Fe, New Mexico

A) There are two choices for polarizing filters: linear and circular. Both achieve the same effect, and you'd be hard pressed to look at an image and tell whether it was shot with a linear or circular polarizer. The circular version is very similar to the linear, but it adds one more optical step to the process.

Let me take a step back and talk about how these filters work. If you consider light as "vibrating," when it hits certain types of surfaces, the light vibrates in a single direction. This single-direction vibrating light is polarized. The polarizing filter can then be used to reduce the polarized light.

Many cameras' autofocusing and metering systems are negatively affected by polarized light, unfortunately. A circular polarizer makes the light entering the lens (and the meter and autofocus system) appear to be unpolarized. The autofocusing and metering systems can then operate correctly.

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