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Tuesday, October 27, 2009

DPP Solutions: Defeating Dust

What you need to know about cleaning your sensor

This Article Features Photo Zoom

Dust is everywhere—even inside your camera where it doesn’t belong. Dust that collects on the imaging sensor can cause tiny blotches to appear on your images. If one or more small spots appear in the same relative position from image to image, you have dirt on your sensor.

1) Delkin SensorScope
Actually, the imaging sensor, be it CCD or CMOS, isn’t directly exposed to the environment. It’s safely protected by a layer of optical glass called a low-pass filter (see sidebar). Therefore, it’s never in contact with airborne contaminants, and it’s somewhat protected from you when you attempt to clean it.

Dust goes everywhere air goes, and it’s attracted by static electricity. Static is a product of friction, like when you shuffle your shoes across a nylon carpet. It’s generated when the tiny glass mirror in your D-SLR moves rapidly through the air, as it does every time you take a picture. That means that D-SLRs are much more prone to dust problems. Dust enters your camera every time you change lenses—even though you can’t see it. That’s another reason why D-SLRs suffer more. In fact, if you know you’ll be working in an environment that’s heavily dust-laden, opt for an all-in-one-type zoom camera that has a nonremovable lens.

While it’s obviously better to avoid dust, it’s also impossible. Although working pros can’t prevent dust from collecting, they can prevent it from ruining their images.

2) VisibleDust Arctic Butterfly
Camera, Heal Thyself
Many cameras use special techniques to clean their imagers automatically. In most cases, the frequency of the cleaning action can be selected from a menu. Clean at power-up, at power-down or both. The cleansing typically involves some sort of shaking or vibration and takes one second or longer to complete. This delay at startup can be annoying, but usually goes unnoticed if scheduled to occur each time your camera shuts down. You also can make most cameras shake on demand.

Olympus developed dust-reduction technology in 2003 that’s included in all of its interchangeable-lens-system cameras. The Super Sonic Wave Filter (SSWF) system uses components such as an ultrasonic motor that can vibrate a glass filter in front of the image sensor at about 30,000 vibrations per second. This occurs in a fraction of a second each time the camera is powered on so that the dust particles are shaken away from the sensor area. The technology has been so successful at removing dust that, according to product manager Sally Smith Clemens, Olympus has a record of “virtually no cameras returned to the company for dust removal.”


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