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How To Know Your Sensor is Dirty
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How To Know Your Sensor is Dirty

See and eliminate dust spots


If you have a digital SLR and change lenses, you have spots on your sensor (and images.) Want to see?

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Photograph a clear sky. Use a long lens for an even tone, set at the smallest aperture--f/22 or whatever you can get. Throw the image out of focus. In Photoshop, desaturate the image and boost contrast. Now you know how dirty your sensor is.

Here is one-quarter of a very dirty sensor:

Cleanup time: You can send the camera out to have the sensor cleaned if you don't mind the expense and time, but for most people the only long-term strategy is to learn to clean it yourself.

DIY: A squeeze bulb that blows air on the sensor is not very effective, especially for older spots that can become almost glued on. Heavier-duty cleaning is done with a brush or solvent-and-swab products. See Dust Busters! to learn more.Use a freshly-charged battery and don't touch the on-off switch or bump the card door open while cleaning.


How to Spot Sensor Dust

Sensor dust spots are much more obvious at small apertures, and against clean areas such as a sky. In images shot with medium apertures they are larger and lighter gray. With wide enough apertures many may not show at all. They are also less obvious in very bright or very dark areas. Here is a portion of a sky shot with a dirty sensor.

The spots are generally in the same places in different exposures, although they can jump around or suddenly appear with mirror and shutter vibration.


Diane Miller is a widely-exhibited freelance photographer who lives north of San Francisco, in the Wine Country, and specializes in fine-art nature photography. Her work, which can be found on her web site,, has been published and exhibited throughout the Pacific Northwest. Many of her images are represented for stock by


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