The Dirt on Digital SLRs' Dust

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Thought you were stymied by the static electricity that glues your clothes together in the dryer? That's nothing compared to what you'll feel the first time dust sticks to your digital SLR's sensor. Nothing mars a blue sky in a thoughtful composition quite like a black splotch of dust.

How Dust Gets In

Today's digital SLR cameras rely on an image sensor--CMOS or CCD--to capture the image. When the camera is on, both types of sensors carry an electrostatic charge that attracts dust and other airborne particles to the sensor (or more precisely, to the low-pass filter just above the sensor).

If you change lenses at a beach, in a park--or anywhere except a filter-protected clean room--chances are you will be hit by dust at some point. Some experts even point to certain zoom lens designs as a source of dust: The push-pull of the zoom could cause dust to get inside the camera.

The shape of the particulates caught inside your camera, and how they will affect your images will vary, depending upon the aperture and focal length you're using.

To determine whether your camera has been affected by dust, shoot a clear blue sky or a smooth white surface that is well lit, and shoot without using a flash, say at f/16 or f/22 (the more stopped down the aperture is, the more likely you are to see any particles on the sensor). If you have a zoom lens, shoot your test shots at a wide angle; if you zoom in, the dust splotch might appear less like a spot, and more like a soft blob. Finally, view your test shots on your PC, using your photo editor to view the shots at 100 percent crop.

Tips for Minimizing Dust

Here are a couple of tips to reduce dust particles in your SLR.

Face the SLR Down: When changing lenses, keep the camera off and facing downward. Have your lenses at the ready to minimize the length of time the sensor is exposed.

Avoid Canned Air: Don't use canned air--the force of its air blast can damage your camera's sensor. If you want to try cleaning it yourself, camera makers usually recommend you use only a handheld air blower, such as Giotto's Rocket Air Blower.

Clean the area around your lens mount: It's easy for dirt and dust to collect around the lens mount over time. Clean this area regularly, to decrease the chance of getting particles into the CCD chamber.

You Have Dust--Now What?

If none of the above remedies do the trick, your options are limited. Most camera warranties don't cover the cleaning of the sensor or its replacement if you damage it. Having a pro shop or camera maker clear the dust can cost you anywhere from $30 to $100 a pop: expensive, yes--but a lot cheaper than buying a new camera.

Few vendors provide adequate information on how to mitigate the dust problem, and even fewer provide a solution.

Olympus offers a dust-reduction system built into its EVolt E-300. A supersonic wave filter vibrates dust off the sensor every time you turn on the camera. If dust still manages to find its way into the camera, Olympus says it will cover the cleaning under warranty.

Canon says that to keep its sensor from attracting dust, an antistatic charge runs whenever the camera is on. Dust may get inside nonetheless, and if it does, Canon will not cover a cleaning under warranty. Canon also does not have a set fee for cleaning the sensor, even if that's all you're sending the camera in for.

Nikon, meanwhile, offers no features in its hardware to help get rid of any dust that does get on the sensor. Instead, it expects users to eliminate dust blotches in post-processing. The catch: You have to shoot in RAW format, shoot a dust reference image (an option in the menu), and then process the first image using the optional $100 Nikon Capture software. The company doesn't include sensor cleanings under warranty, but it will clean your sensor for about $30 plus shipping both ways.

Most vendors don't provide satisfactory details on how to clean the filter yourself, if you're so inclined. Nikon's roundabout approach is typical of how camera makers deal with dust. Nikon's manuals don't really get into the dust issue per se, but instead bury the information. (For example, the D50's manual stashes info on cleaning its sensor under the obscure title, "The Low-Pass Filter," way back on page 116). To Nikon's credit, the D50's manual does say up front--on page 7--to turn off the camera before changing lenses.

Fujifilm does the best job of educating its users on the dust issue: The company provides a PDF on its Web site that not only provides an illustrated step-by-step guide to cleaning the CCD sensor, but also recommends a third-party solution: Eclipse Optic Cleaner fluid and Sensor Swab wipes from Photographic Solutions.

Melissa J. Perenson

This story, "The Dirt on Digital SLRs' Dust" was originally published by PCWorld.

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