Removing dust from DSLR cameras
by Lorenzo Comolli

Cleaning the sensors of DSLR cameras is a relatively new iussue, indeed in the past the film cameras have not this kind of problems. It's bound to happen that dust deposit on the surface of the sensor, and in this way it projects a shadow in all the shoots. Indeed the dust deposits on a protective glass, a few fraction of millimeters distant from the sensor; for this reason the cleaning can be done without to much troublings because you'll not really hurt the delicate sensor. The dust shadows is more visible when we shoot using very closed aperture ratios, because the projected shadow is smaller and sharpened; another condition for visibility of dust is an uniform background, such as a clear sky.

The measurement of dust quantity
Before cleaning the sensor is fundamental to verify if this operation is really necessary: some small piece of dust is normal and tolerable, and it isn't worth to clean the sensor.
To examine how much dust is present you'll need an objective with a very closed apertura: i.e. the Canon EFS 18-55mm, if used at 55mm, can be closed at f/36. And more you'll need a uniform light source: a very good source is a clear sky at zenith, but is't ok also a white sheet of paper, defocused, or a flat-field-ometer like the one shown here below, made for other purposes (obtain a flat-field for use with astronomical CCDs). The result of such a test is in this figure.

Here the sensor was not so dirty, but two small bristles are visible on the bottom. At left the raw image, at right the enhanced one.

My cleaning procedure
IMPORTANT NOTICE: all the operations here described has been tested and never damaged my cameras. However be aware that the author does not assume any responsability for eventual damages to the reader cameras using the procedure here described.

It's necessary to obtain the following items:

The necessary stuff for the cleaning, including my flat-field-ometer for capturing an uniform background.

Here is the procedure to clean the sensor:
All those operations have to be made very quickly, I usually need a minute or so. I recommend to try before the procedure on a less critical glass, like the front lens of an objective.

In the end you'll have to remount the objective on the DSLR and now verify the sensor cleanness. If the sensor was really dirty, maybe you'll need to repeat the procedure.

Here is the result of the cleaning (at left a raw image, at right a very enhanched one).

This page explain how to clean the DSLR cameras sensors with a very modest cost, and without so much effort. On the market there are many special liquids and specific kits, some of with very expensive and hard to import. My personal opinion, at the light of the results here shown, is that they are not necessary.

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