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One Filter

July 25, 2008 - Dave Hecei
Digital photography has definitely changed the way we take pictures. Not only do we have the freedom to experiment with shots, because we no longer have to pay for expensive film and processing, but working with digital images on the computer allows for even more creativity. With film, you had to carry lots of filters for your lenses to correct color or do special effects. This is all done in the computer now. Except for one thing.

The polarizing filter performs a very special task that, as of yet, cannot be duplicated in the computer. Digital SLRs have adjustable white balances, so color correction filters are no longer needed. Photoshop has the ability to adjust the brightness levels in a scene, so graduated filters are no longer needed. Polarizing filters are used to remove glare off of water or reflections on glass. They can also deepen the blue of the sky and whiten the clouds. Polarizers can also help cut through haze on a muggy day. Photoshop cannot do this.

So the one filter that everyone still needs is the mighty Polarizer. If you've never used a filter before, which may be the case if you are new to DSLRs, a filter fits on the end of your lens. There are small threads on every lens so you need to know what size your lens takes, usually it will say on the lens or you can look in the lens manual. Common filter sizes are 49, 52, 55, 58, 62, 67, 72, and 77mm. Another place to look is the inside of the snap on lens cap, most have the filter size written there.

For digital cameras you do need a special type of polarizer. Older manual focus film cameras can use a standard polarizer, or what is now called a linear polarizer. Linear filters do not work with autofocus film or digital SLRs. Autofocus SLRs need to split the light coming through the lens, most of it going to the viewfinder but part of it going to the auto-focus sensor. This light going to the sensor becomes polarized. If you use a linear polarizer, the light going to the auto focus sensor can get cancelled out and the camera won't be able to focus.

Digital SLRs need to use a special type of polarizer called the Circular Polarizer. Of course this is a little bit more expensive than a standard polarizer, but since the popularity of DSLRs is very high, prices have come down quite a bit. Prices will vary with the size of the filter. Try not to buy the cheapest filter you can find. A cheap filter can make your expensive SLR lens…well look cheap. There are a couple companies that specialize in filters. Hoya, Tiffen, and B&W are the big ones.

Polarizing filters are variable. When you attach the filter to you lens you will note that the filter rotates in its frame. With the filter attached, look through the viewfinder and rotate the filter slowly. As you slowly rotate the filter you should see the scene change ever so slightly. Polarizers work best outdoors, but inside it will help reduce reflections in windows or on other glass surfaces (will not work with mirrors). If you are shooting outside on a partly cloudy day, you should see the clouds become brighter and the sky should darken. As you rotate it more, the effect should lessen.

Another time I like to use a polarizer is when shooting foliage. This can be either the deep green meadow or sparse forest area, or in the autumn shooting the fall leaves. Using a polarizing filter will remove the glare that you don’t notice but robs the scene of saturated color.

Because of its special abilities, a polarizer is the one filter that all DSLRs should have.


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Circular screw on polarizing filter.