TechniqueCleaning your digital sensor 52 | 53

D ust’s purpose in life is to get everywhere. And it does. Try as you might, you won’t stop it from creeping into your digital camera and finding a home on the image sensor. The sensor is made up of millions of light-sensitive elements, each around 6 to 8µm

square. It does not need a very large piece of dust or dirt to cover one or more of these elements, or pixels. If a pixel is obscured, it does not receive much light and so that portion of the image will record as grey. These grey areas are most noticeable in light-toned areas of the photograph.

Why all the fuss now?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. But film is transient – it moves on after each exposure – so a speck of dust on film will affect one exposure, and then be transported along the back of the camera with the film.

Is your sensor dirty?Do you have dust on the sensor of your digital camera? Can you see small grey spots in light-toned areas, such as skies? If not, forget about dust and concentrate on taking pictures.

The marks 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 lies on top of the sensor. The gap between the sensor and the dust is enough to throw the spots out-of-focus and allow some light to creep underneath.

A more thorough test is to photograph a white wall or a sheet of white paper. Use 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 focusing distance. Select aperture-priority (Av) shooting mode on the camera’s command dial and set the smallest aperture (f22, for example). Now make 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 the test. Transfer the image file to a computer and view the result with any good imaging 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 large areas of light tones in your images? If so, cleaning the sensor might be worthwhile.

We covered the dilemma of dust in digital cameras only a couple of years ago (‘Dust busting’, June 2004), but it won’t go away. So Richard Ford has another go at cleaning up.

TechniqueCleaning your digital sensor

Say goodbye to dust

DIRECTION OF FILM TRAVEL

DUST ONFILM SURFACE35mm

FILMCARTRIDGE

CAMERATAKE-UPSPOOL

DUST ON FILM ONLY AFFECTS A SINGLE FRAME

DAVID NEWTON

TechniqueCleaning your digital sensor 54 | 55

left Switch the camera off before changing the lens. This reduces the static charge on the sensor and stops it attracting dust. Canon is working on ways to reduce the static charge in the sensor, but has published very little information on this.

right Never leave the camera with the lens mount open. When you remove a lens, replace it immediately with another or attach the camera body cap.

left Avoid changing lenses in dusty situations. If you have to change a lens in these conditions, hold the camera with the lens mount facing down to reduce the risk of dust falling into the opening.

right Keep the body cap free from dust. Did you know that the body cap and lens cap attach to each other? This will keep the inside of both caps clean when a lens is on the camera.

Prevention is better than cureYou can’t stop dust getting into your digital camera, but you can reduce the risk a little using one or more of these simple procedures.

Whatever precautions you take, one day your sensor will need cleaning. Canon approves only two methods. The first you can try yourself using a blower brush (page 56). The second means sending the camera to a Canon Service Centre, which involves a significant fee and the loss of the camera for a period of time.

There are also several techniques not approved by Canon. These methods are covered on the following pages, but are not endorsed by EOS magazine. If you want to try them it is at your own risk – we don’t accept any liability for any damage you might cause to your camera.

The risk to the sensor is fairly small, because it is not actually the sensor which gets dirty. The sensor is protected by a glass filter and the dust settles on the surface of this. 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 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 camera 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 (see next page). If these blades accidentally close while you are touching the sensor assembly with cleaning aids, a lot of expensive damage will occur. This will not be covered by your camera warranty or insurance. Do not attempt this type of cleaning unless you feel confident about your ability to do it without damaging your camera.

EOS D30, D60Sensor cleaning can only be done from mains power – it won’t work from battery power. Connect Compact Power Adapter CA-PS400 to a mains socket and plug DC Coupler DR-400 into the back of the adapter unit. The other end of the DC Coupler is a dummy battery which is inserted into the camera. Both the adapter (the battery charger) and the DC Coupler are supplied as standard with the camera. Set Custom Function 13-1 (Sensor cleaning – Enable). The message ‘Clean’ will appear on the LCD panel. Press the shutter button to raise the reflex mirror and open the shutter. After cleaning, turn the main switch to ‘off’. The shutter will close and the mirror drop. Turn the main switch back to ‘on’ to start shooting. (D30 manual page 117; D60 manual page 115)

EOS 10D, 20D, 300D (Digital Rebel), 350D (Digital Rebel XT), 5DSensor cleaning can be done using the camera battery power, but fully recharge the battery before you start. You can also run the camera from mains power using the optional AC Adapter Kit ACK-E2. Select item ‘Sensor clean’ from the menu and press the ‘Set’ button. Select ‘OK’ and press ‘Set’ again. The mirror will lock up, the shutter will open and ‘Clean’ will appear on the LCD panel. After cleaning, turn the main camera switch to ‘off’. The shutter will close and the mirror fall. Turn the main switch to ‘on’ to start shooting. The Sensor clean item can be found in the yellow setup area of the 10D menu; setup screen of the 20D and 5D menus; and setup2 screen of the 300D and 350D menus. (10D manual page 156; 20D manual page 36; 300D manual page 34; 350D manual page 39; 5D manual page 42)

EOS 1D, 1D Mark II, 1D Mark II N, 1Ds, 1Ds Mark IISensor cleaning can be done using the camera battery power, but fully recharge the battery before you start. You can also run the camera from mains power using the supplied DC Coupler Kit DCK-E1. While pressing the ‘Menu’ button, select the setup menu screen (setup2 menu on the 1D Mark II, 1D Mark II N and 1Ds Mark II). While pressing the ‘Select’ button, select ‘Sensor cleaning’. Release and press the ‘Select’ button and select ‘OK’. Release the ‘Select’ button and the LCD screen will show ‘CCd Cln’. Press the shutter button and the mirror will lock up and the shutter will open. (1D manual page 150; 1D Mark II manual page 40; 1D Mark II N manual page 48; 1Ds manual page 150; 1Ds Mark II manual page 40)

The EOS sensor cleaning mode does not clean the sensor – it simply gives access to the sensor for cleaning.

Opening the shutterAll EOS digital cameras have a special sensor cleaning mode. This gives access to the sensor by raising the reflex mirror and opening the shutter blades. Canon recommends that you run the camera from a mains power supply, via a DC coupler, when using this mode. With most cameras, you can use the 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 with the risk of expensive damage to the camera. Even running the camera from mains power is not risk-free – there could be a power failure while you are cleaning the sensor (so avoid this procedure during thunderstorms). Brief details for switching to cleaning mode are given here, but read the instruction manual before you start.

Cleaning the sensor

Normal mode Sensor cleaning mode

TechniqueCleaning your digital sensor 56 | 57

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

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 a stick. But this is no ordinary rubber. The material has a built-in tackiness, which means that dust

Grabbing the speckswill 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 particle will come away. 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 it’s own. We use SpeckGrabber with EOS magazine cameras, but it is not approved by Canon and might affect your camera warranty.

Visible Dust brushesWhile a blower brush will move lightly settled dust, it may not have any effect on dust which has a good grip on the sensor. A 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, though expensive, seem to have the right

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 at www.visibledust.com before proceeding. This technique is not approved by Canon and its use may affect your camera warranty. We use Visible Dust brushes at EOS magazine.

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 use the compressed air inside the camera – it may cause expensive damage). Ideally, a single sweep of the brush across the sensor will clear the dust. If not,

Swabbing the sensorand wipe it firmly over the sensor. The end of the spatula is flexible, which means that it is difficult to apply excessive pressure. If you want to do a second swab, just reverse the motion, so that the opposite edge of the spatula is drawn back across the sensor (this avoids any dust or dirt from the first sweep being pressed back into the surface or the

glass). We are using Sensor Swabs at EOS magazine, along with Eclipse fluid (ultra-refined methanol). Both are produced by Photographic Solutions Inc. Take a look at www.photosol.com/swabproduct.htm for details and animated instructions. Warning: this technique is not approved by Canon and its use may affect your camera warranty.

As soon as the sensor clean 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 or the camera shutter blinds during the cleaning process, but we have yet to hear of anyone having problems. We sell a selection of cleaning products, including those that we regularly use, in our online shop (see page 81).

Blowing techniqueThe rubber blower technique is the only user-cleaning method approved by Canon. 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. These are often sold with a brush attachment and were originally used for cleaning film negatives and slides. Remove the brush so that 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 use compressed air from cans – it often contains liquid propellants which will smear the sensor.

Cleaning techniques

The ‘Repair’ window in Canon’s Digital Photo Professional software provides an easy way to get rid of dark spots on your photographs. Simply position the

green circle over the affected area and ‘click’ the computer mouse. The size of the circle can be adjusted with the ‘Radius’ control bar to suit the mark.

Software solutionsSoftware solutions

Despite all your attempts at preventing dust from getting to the sensor, and various methods of cleaning, you may find that some of your exposures are spoilt by grey marks. All is not lost. It’s quite easy – and a lot safer – to clean up on a computer. Simply download the images files to your hard drive and open up an image in any good imaging software, such as Photoshop Elements or ArcSoft PhotoStudio (supplied free with many EOS camera models), or Photoshop. These all have a ‘clone tool’, or similar function, which allows you to select an area close to the dust speck, and copy this over the mark. With a little skill you can retouch the image so that it is impossible to see where the spots were.

Canon’s own imaging software – Digital Photo Professional – goes one step further. It not only has a standard clone function, but also offers automatic retouching. Canon has built its ‘FARE’ system into the software – the same technology used in scanners to overcome the problems of dust. If you choose ‘Repair (dark)’ from the Tools > Start Stamp Tool menu, and then select a small area which includes the dust speck, the mark will disappear like magic. Choosing ‘Repair (light)’ will work the same magic on white spots.

Digital Photo Professional is on the EOS Digital Solutions disk supplied with a number of EOS digital models, but you may need to update the software to the latest version to take advantage of this auto-retouch feature. Go to www.canon.co.uk and follow the ‘Download software’ link.