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Polarizing filters

Linear or circular? Doug Wilcox (Yahoo!, FZ10 group, 28 October 2004)...

Until cameras started using autofocus there was no need for a circular polarizer. They developed the Circular polarizer for these cameras. The older Linear polarizers did fool some auto-focus systems so they developed the circular polarizers. You can buy a circular polarizer and use it on any camera while the Linear polarizer might not work on some auto-focus cameras. Linear polarizers are probably cheaper because there are so many of them still out there. You can get a pretty good used one really cheap. The FZ10 seems to work fine with either type.
Steve Thuman (Yahoo! FZ10 group, 22 October 2004) writes...

On the FZ10 it is somewhat hard to see the effect of the polarizer in the viewfinder/LCD {harder than on an SLR}. There is a slight delay between the time you rotate the polarizer to adjust the polarizing effect and the time it shows in the viewfinder. So adjust very slowly until you get used to it. After using one for awhile your eye will train itself to see the effect better. And use it sparingly whenever there is sky in the scene. Over polarizing the sky makes it dark and rather greyish.
Polarizer -- Dr. Ching Kuang-Shene's very helpful and informative polarizer page. Much of the information on Dr. Ching's page is also contained in the following post by Paul Milholland (Yahoo! FZ10 group, 22 October 2004)...

A polarizer (PL) is something that every photographer who wants to take really nice photos should have in his/her bag or pocket. A PL basically looks like two dark grey filters screwed together. The front half of the filter can be rotated to control the amount of polarization. As you rotate the front of the PL, it allows more or less polarized light to reach the camera's CCD {charged couple device i.e. `digital film'}. BTW, it's a good idea to rotate the PL as though you were trying to screw it into the front of the lens, to avoid accidentally unscrewing it from the lens...

The quick and dirty way to locate polarized light is to remember that it occurs at a 90-degree angle from the sun. When the sun is overhead, there's a band of polarized light pretty much surrounding you. If the sun is lower in the sky, you'll need to do a quick recalculation of where the polarized light will be. The classic way to do that is to make a pretend pistol with your hand, with your thumb sticking straight up. If you point either your thumb or your index finger at the sun, the other finger will be aiming in the direction of some polarized light.

A lot of people think a PL is primarily for darkening blue sky and making the clouds stand out more distinctly. It certainly does that, although it's easy to overdo it in that context and leave yourself with skies that border on navy blue. Not a good look...At least with a digital camera, you can review the shot and dial in a little more or less polarization for the next shot.

A polarizer can also be used to reduce reflected light coming off water, grass, foliage and flowers. If you've ever worn polarized sunglasses, you have an idea of how a polarizer can punch up the color of the things I just mentioned. Grass and trees look greener, flower colors are more vibrant, and the glare off a body of water is reduced. I'd be willing to bet that most of the knock-your-socks-off shots you've seen of fall foliage were taken with a polarizer to reduce the reflected light off the leaves, allowing the reds and yellows to really show their stuff...

You can also use a polarizer to cut through reflections coming off store or car windows, allowing you to take a photo of what's inside. You need to shoot from an angle for that to work, however. A straight-on shot with a PL of a glass surface doesn't allow the filter to work its magic.

Now for the bad news: using a PL will cost you a stop-and-a-half to two stops of light. Not a big problem if you've got plenty of light, but if the light is marginal you may wind up having to settle for a larger aperture to keep your shutter speed up...


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David Fong 2009-09-04