You can easily perform your own tests to check the
cleanliness and integrity of the ccd image sensor.
You need a target:
- The simplest and fastest way is to use a clear blue sky as background for your test shots.
- But you can also use a piece of white non-shiny cardboard as background as long as you have reasonably even illuminating on the board.
The Test Exposures:
- Set the camera image resolution to the highest setting you normally use and zoom in close.
- Set APERTURE PRIORITY and adjust the aperture to f:11. (You really only need a higher f:stop if you are super critical and need high enlargement. Most lenses perform best at f:5.6 to f:11 and should be judged this way).
- Place the camera a short distance from the cardboard so the white surface completely fills the frame. Set the focus to manually to INFINITY (switch off Auto Focus).
- If you use a blue sky as background set focus to the CLOSEST distance. This is to avoid any focus point that could misinterpret the result.
- Expose a couple of images, then inspect the result in your imaging program at 100% to 200% magnification.
Evaluation:
 Dust, dirt, and fibers will show up as darker irregular spots and marks on the image such as on sample test on the left.
If the surface is clean you should see only the rectangular or square pixels when viewing at high magnification. Pixels may vary slightly in density - this is normal and not a concern or dust indication.
Most loose particles can be removed with a D-SLR Sensor Brush and Air Blower (see next page for results). A slightly more expensive but quicker method is using the DUST-AID kit with adhesive pads!
You may also discover that the sensor or filter surface has been smeared. This can happen if canned air has been used or if the sensor surface has been touched by contaminated cleaning material.
The test picture on the left show lots of smears. Using a brush here will not remove the spots and may even contaminate the brush. Only physical cleaning will help here!
 If you are viewing the test images at about 200% magnification and you note faint spots covering an area less than about 12 pixels it is unlikely they will be noticeable on a normal size print.
Occasionally you may notice very bright individual pixels (hot pixels) or black pixels (dead pixels).
Bright pixels can be caused by an electrical aberration and may disappear again. Try removing power from the camera for a few hours. Then use any reset function your particular camera may have, shoot a series of photos of a blue sky, then recheck.
If the faulty pixel continues to show in the same spot it may be worth checking with the manufacturer to ascertain whether their adjustment software can restore or compensate pixel errors.
Alternately you may just have to live with it and edit them out in your image software program.
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