Say goodbye to dust, dusts purpose in life is to get everywhere.  And it does, try as you might, you won't stop it from creeping into digital camera and finding a home on your image sensor.  The sensor is made up of millions of light sensitive elements, each around 6 to 8um Square.  It does not need a very large piece of dust or dirt to cover one or more of these elements, or pixels.  If the pixel is obscured, it does not receive much light and so that portion of the image is recorded as grey.  These grey areas are most notable in the light toned areas of the photograph.

If dust is such a problem for digital cameras, why doesn't it affect film users?  Well, it does, but with less serious consequences.  In a digital camera, the sensor is fixed in position.  If a speck of dust becomes attached, it will make its mark on every subsequent exposure.  The film is transient “it moves on the on after each exposure”.  So a speck of dust on the film, will effect only one exposure, and then be transported along the back of the camera with the film.

Do you have dust on the sensor of a digital camera?  Can you see small grey spots in the lightly toned areas, such as skies?  If not, forget about dust and concentrate on taking pictures.  The spots will be grey and fuzzy because the dust is not actually in contact with the surface of the sensor.  Instead, dust rests on the surface of the low pass filter, which sits on top of the sensor.  The gap between the sensor and the dust is enough to throw the spot out of focus and allowed some light to creep underneath.  A more thorough test is to photograph a white wall or white sheet of paper.  Using a telephoto lens, if you have one, or a zoom set to its longest focal length.  Don't focus on the subject set the minimum focus distance.  Select aperture priority shooting mode on the cameras

Command dial and set the smallest aperture (f/22 or above, for example). Now take an exposure. The shutter speed will probably be quite slow, but there is no need for a tripod as subject Blur will not interfere with this test. Transfer the image file to your computer and view the results with a good image software at a magnification of 100%. You will almost certainly see some grey marks - you have to decide if these are significant.  Do you regularly have larger areas of light tones in your images?  If so, cleaning the sensor might be worthwhile.

 

Whatever precautions you take, one day, your sensor will need cleaning.  There are generally several methods to do this that the manufacturers approve. The first you can try yourself using a blower Brush and try to remove the dust yourself. The second means sending the camera back to the manufacturers or service centre, this involves a significant fee and the loss of the camera for period of time.

There are also several techniques not approved by manufacturers.  These methods are covered during the following article.  (If you want to try these at your own risk, we do not accept any liability for the damage you might cause to your camera.)

The risk to the sensor is fairly small, because it's not actually the sensor which gets dirty.  The sensor is protected by a glass filter and the dust settles on the surface and this will stop it touching the sensor, so removing the dust is rather like cleaning a lens filter - there is a risk of scratching the filter, but this risk is quite small.  If you follow the instructions correctly and carefully.  On the other hand, if you do scratch the sensor cover, the replacement cost will be a lot more than the cost of most lens filters. The real danger in sensor cleaning is damage to the cameras shutter.  Except during an exposure, the sensor is covered by the blades of the shutter.  To access the sensor, you need to open the blades.  If these blades accidentally closed while you're touching the sensor assembly with the cleaning Kit, lots of expensive damage will occur.  This will not be covered by the camera warranty or camera insurance.  Do not attempt this type of cleaning unless you feel comfortable about your ability to do so without damaging your camera.

1. You cannot stop dust getting onto a digital camera, but you can reduce the risk a little using one or more of these simple procedures.
2. Switch the camera off before changing the lens.  This reduces the static charge of the sensor and stops it attracting dust.  All manufacturers are working on ways to reduce the static charge in the sensor, but have not yet published any information on these tests.
3. Never leave the camera with the lens mount open.  When you remove the lens, replace it immediately with another or attach the camera body cap.
4. Avoid changing lenses in dusty situations.  If you have to change your lens in these conditions, hold the camera with the lens mount facing down to reduce the risk of dust falling into the opening.
5. Keep the body free from dust.  Did you know that the body and lens caps attach to each other? This will keep the inside of both clean when the lenses on the camera.

 

 

All digital camera manufacturers have a special sensor cleaning mode.  This gives access to the sensor by raising the reflex mirror and opening the shutter blades.  All manufacturers recommend that you run the camera from a mains power supply, via a DC. coupler, when using this mode.  With some cameras, you can use this mode, with just the camera battery, but make sure the battery is fully charged.  If battery power fails during cleaning, the shutter blades could close on the cleaning tool and risk expensive damage to the camera.  Even running the camera from mains power is not risk-free - there could be a power failure  while you're cleaning the sensor (so avoid cleaning the sensor during a thunderstorm).

As soon as the sensor cleaning mode has raised the reflex mirror and opened the shutter curtains, you need to work quickly.  Leaving the sensor assembly exposed increases the risk of more dust settling.  It is possible to damage the filter covering the sensor while the camera shutter blades are open during the cleaning process, but we have yet to hear of anyone having problems.

 

The rubber blower technique is the only method of cleaning approved by  most manufacturers.  It is non invasive, which means that even if the shutter closes during the procedure you are unlikely to damage the camera.  All you need is a rubber blower bulb (see on right).  These are often sold with a brush attachment and were originally used for cleaning film negatives and slides.  Remove the brush, so then you have a device which gives short jets of air as you give the bulb a sharp squeeze.  With the camera in sensor cleaning mode, and the lens removed, place the tip of the blower just inside the camera lens mount and give a few bursts.  This will dislodge any dust specks which are resting on the sensor.  With luck, the dust will be blown out of the camera.  Do not used compressed air from cans - it often contains liquid propellants which will smear the sensor.
 

The visible dust brushes.

While a blower Brush will remove lightly settled dust, it may not have the effect on dust which has a good grip on the sensor.  Tougher technique is needed.  Brushing the surface of the sensor can be effective, but not with any old brush.  You need one which is ultra-clean and just the right size for the sensor.  Visible dust brushes, although expensive, seemed to have the right specification.  They work by not merely brushing the dust away, but by using static to attract the dust onto the bristles.  You also need a can of compressed air to blast the Brush before and after sweeping it across the sensor (never used compressed air inside the camera, it could cause expensive damage).  Ideally, a single sweep of the brush across the sensor will clear the dust.  If not, two or three sweeps can be used, with compressed air blasts on the brush between each sweep.  Visible dust brushes come in different sizes to suit different sensor sizes.  Read all the information on dust brushes, before proceeding with this technique.

 

Swabbing the sensor

If the idea of brushing the sensor makes you nervous, the following technique will send you into a blind panic.  It uses a plastic spatula, with a clean paper cover impregnated with liquid to swab the sensor.  The liquid is usually methanol - an alcohol which evaporates rapidly without leaving any residue.  You apply just a few drops of methanol to the end of the swab and swipe it firmly over the sensor.  The end of the spatula is fixed, which means that it is difficult to apply excessive pressure.  If you wanted to do a second swab, just reversed the motion, so that the opposite edge of the spatula is drawn back across the sensor (this avoids any dust from the first sweep being pressed back into the surface of the glass).

 

Grabbing the specks.

Finally, there is a useful gadget for removing larger specks of dust from the sensor.  Called "SpeckGrabber", it is a tiny piece of rubber on the end of the stick.  This is no ordinary rubber, the material has a built in tackiness, which means that dust will stick to it.  To use, you wipe the rubber with a special cleaning tissue and then simply touch the surface of the sensor with the "SpeckGrabber".  The dust particles will come away and leave the sensor clean.  This is a very selective cleaning method, not suitable for cleaning the entire sensor area, so you may well want to use it in addition to one of the other techniques rather than on its own.

 

Software solutions

Despite all your attendance at preventing dust from getting to the sensor, and various methods of cleaning, you may find that some of your exposure are still spoilt with grey marks. All is not lost.  It's quite easy - and a lot safer to clean up on a computer.  Simply download the image files to your hard drive and open an image.  There are some good image software, such as Photoshop Elements, Archsoft Photostudio or Photoshop CS2 / 3. These all have a “clone tool” or similar function, which allows you to select an area close to the dust spec, and copy this over the mark.  With a little skill, you can re-touch the image so that it is impossible to see where the spots were.