Digital Focus: Polarizing Lenses

Block out distortion and take better photos with this common lense.

Dave Johnson

Feature: Snappier Pictures With a Polarizing Filter

The use of polarizing filters is one of the best-kept secrets of the photography world. Pros know all about these filters, and they carry them on every photo shoot. A polarizing lens can enhance the colors in your photo and deepen the contrast. It can change a so-so picture into one that has a lot of oomph (yes, that's a technical term).

Polarizers have the seemingly magical property of being able to reduce or eliminate glare and reflections in some shiny surfaces like glass and water. If you're shooting through a display case, for instance, you can rotate and adjust your polarizing lens to eliminate most of the reflections and better photograph what's under the glass. Glare decreases your camera's ability to "see" objects you want to photograph, and it can make the sky look washed out and less blue than it really is.

Sound good to you? I thought so. Even better, any digital camera can benefit from a polarizing lens: Polarizers work the same in the digital realm as they do in the world of film.

Finding a Polarizer

Your digital camera may be able to use a standard polarizing filter that's sold for film cameras--it depends upon whether your camera has threads on the front of its lens. Visit your local camera shop or check out Tiffen to see if you can simply screw a polarizer on to the front of your lens. If not, some cameras have filter adapters that snap or clip onto the front of the camera.

Be sure to get the right kind of polarizer. Filter vendors sell two kinds of polarizers: linear and circular. Virtually all photography is done with circular polarizers. If you're offered a linear polarizer, don't buy it: It won't work with a digital camera and will simply confuse the sensor.

One other, makeshift solution: You can hold a pair of polarized sunglasses in front of the lens at the proper angle relative to the reflecting surface. (To get this angle, just watch the LCD on your camera as you fiddle with the sunglasses until the image looks right to you.) Don't laugh: It works.

Using a Polarizer

As I mentioned, your polarizing filter rotates. As it turns, the effect of the filter changes, going from filtering out no glare to filtering out the maximum amount. What suits your picture? That's up to you--just rotate the polarizer while looking through the LCD on your camera. You'll see the effects on your image in real time.

You should also keep an eye on the sun's position in the sky. Polarizing filters work best when the sun is to your left or right, and they have no effect if you've got your camera pointed directly toward or away from the sun.

As previously noted, one of your polarizer's most important uses is to minimize reflections from glass or water. (It won't have any effect on reflections from metal objects, though.) You'll want to make sure you use the most effective technique to achieve the best results.

Suppose you're trying to photograph jewelry through a display case. Just as you need to position the camera in the proper position relative to the sun, you'll get better results when you shoot through the glass at the proper angle. You can't shoot directly into glass or water (with the camera lens perpendicular to the reflecting surface) and expect to get good results. Instead, the camera has to be at an angle to the surface. The best angle is about 34 degrees; just experiment a bit and you'll find the right angle for your job.

Dave's Favorites: Internal 7-in-1 Digital Media Reader

Thanks to digital cameras, MP3 players, and PDAs, memory cards have become extremely common. Secure Digital and CompactFlash cards and Memory Sticks are now being used to move files, as well as to store pictures from your digital camera. How much easier would it be to just pop a memory card into a reader attached to your PC than to untangle your camera's USB cable? I've long advocated desktop memory card readers (like Dazzle's 6-in-1) as an easy way to move pictures between the camera and computer. And now I've found an even better option.

Y-E Data's Internal 7 in 1 Drive combines a traditional floppy drive with a 6-in-1 card reader--yet the whole thing fits in a standard 3.5-inch floppy disk drive bay. It attaches to the floppy controller port on the motherboard via a floppy data cable; you'll need a relatively new system that has an available USB connector on the motherboard. If you have an older system--like a Pentium III-based PC--you may not be able to take advantage of this gadget.

Of course, the Y-E Data drive requires you to muck around inside your PC. If you aren't much of a tinkerer, this nifty little combo drive might not be for you. And if you're still getting useful life out of an older system that has only a couple of integrated USB ports, you'll also have to pass. But if you can use this drive, it's a real pleasure. I discovered it recently when I was upgrading to a new PC, and the installation proved to be quite simple. In my estimation, anyone who can tell an IDE cable from an FDD cable should be able to install it in about ten minutes.

Once installed, the 7 in 1 Drive works just like any floppy drive. You can also insert CompactFlash, MultiMediaCard, and Secure Digital media, along with Memory Sticks and Microdrives. Of the common camera media, only the new XD Picture Card isn't supported. Personally, I was happy to get my Dazzle 6-in-1 card reader off my desk, and I'd recommend Y-E Data's product to anyone who wants to reclaim some space. It's available for about $89--go to the company's Web site for a list of retailers.

Q&A: How Long Will Your Camera Last?

For a time on the rec.photo.digital newsgroup, there was a thread about a camera becoming defective and progressively underexposing pictures more and more. This thread generated a lot of conversation about the expected lifetime of CCD and CMOS sensors in digital cameras. Many folks said, "If you get three years before the sensor goes out, you're lucky." Other comments were along the lines of, "You don't buy a digital camera, you just rent it until the sensor goes bad--which is inevitable." Have you heard anything about the image sensors they are putting in these things? What type of life expectancy do they have?

--Mike Tinsley, New York

That's an excellent question, Mike. I didn't know the answer, but I was intrigued--so I posed it to Kodak. A representative obligingly stepped up to the plate.

Helen Titus, a spokesperson for Kodak's Image Sensor Solutions--the division that manufactures the CCD sensor for the company's digital cameras--told me that Kodak performs "accelerated life testing" on its sensors by running them at high temperatures for several thousand hours, right to the point of failure. Engineers, she says, can translate that into an expected lifetime for the sensor in normal operation at everyday temperatures and more typical on-and-off usage.

"We find that the sensors last for tens of thousands of hours in continuous usage without any degradation to their ability to capture photos," Titus says. "That adds up to many years of normal use. The CCD is not the component that will fail first."

Martin Reynolds, a digital imaging analyst at Gartner, agreed with Kodak's assessment. "Those sensors are pretty robust little devices with no long-term failure mechanisms." His only caveat? One I've written about before: "If you expose the CCD directly at the sun, you might cause some damage. But even then it would take an extraordinary amount of energy to cause deterioration."

So, while it's always possible for an image sensor to fail early or behave improperly, it sounds like the majority of digital cameras shouldn't suffer from premature image degradation due to the CCD or CMOS sensor.

Hot Pic of the Week

Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality and technique. Every month, the best of the weekly winners gets a prize valued at between $15 and $50.

Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.

This week's Hot Pic: "Secrets," by George Anderson, Barre, Vermont

About this week's winning photo, George writes: "A simple photo with simple effects applied (I added reflection and spot lighting) resulted in this rather startling image. It reminds me that nature has many dimensions, not all of which are usually visible to us."

George adds that the colors in the middle of the image are the result of lens flare--he didn't add or enhance them.

We want your feedback! Send your comments, questions, and suggestions about the newsletter itself to comments@bydavejohnson.com. If you have a question that you'd like to see answered in the weekly Q&A, send it to question@bydavejohnson.com.

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