A do-it-yourself guide to getting rid of dust from your camera’s sensor

You don’t usually notice it until it’s too late – I didn’t.

Returning from a busy day out with my camera having shot several hundred images was not the best time to discover that minute specs of dust had found their way onto the camera’s sensor.

Judging by the number of posts to digital photography forums and the efforts manufacturers are making to combat it, sensor dust is becoming one of the biggest problems to afflict digital SLR (single lens reflex) camera users.

It consists of dark splodges on your pictures, most easily spotted (no pun intended) in light areas of uniform tone such as clear skies.

The dust gets there when you change lenses – either finding its way into the camera body while there’s no lens on it, or lying in wait on the body cap, the rear lens cap, or the lens itself.

Once inside the camera, dust is attracted onto the CCD (charge-coupled device) sensor when it becomes charged – in other words, when you take a picture.

The first line of defence is to do everything you can to avoid dust entering your camera in the first place. That means keeping lenses and caps scrupulously clean and taking care when you change lenses to expose the camera for the minimum possible time.

This is easier said than done with only one pair of hands, but I try to have the new lens ready before I take the old one off and remove and replace rear caps as quickly as possible.

Theoretically, at least, it also helps to hold the camera body facing downwards, using gravity to your advantage.

Dust defenders
Some camera manufacturers, most notably Olympus and Sony, have implemented hardware dust defences.

Olympus’ first Four Thirds (which refers to the physical format of the CCD) digital SLR the E-1, and its more recent E-series models, feature a supersonic wave filter (SSWF) in front of the CCD. It vibrates at high frequency to shake off any dust particles (you can see it in action by clicking here.

Sony’s new Alpha 100 digital SLR has a two-fold dust defence system. First, an anti-static coating on the low-pass filter in front of the sensor prevents dust from being attracted to it. Second, it uses the actuators of the ‘Super Steady Shot’ anti-camera shake system to vibrate the sensor and shake off any dust.

Like the Olympus SSWF, Sony’s system is activated whenever you switch on the camera, so the problem of dust spots on your photos should never arise. For extremely tenacious particles, however, you can activate it from the menu system.

Blow it off
For cameras that don’t shake themselves clean, the most widely recommended and safest method of removing dust and particles from the sensor is to use the blower part of a blower brush with the brush head removed.

To expose the sensor you’ll need to flip up the mirror and open the shutter.

Some cameras have a cleaning mode that does this without charging the sensor, avoiding the potential for attracting further dust. In the absence of this, you’ll need to set the shutter speed to the ‘B’ setting.

If you have a mains adapter, use it to avoid the possibility of the battery discharging and the shutter closing while you’re in the middle of cleaning. Failing that, take the precaution of making sure the battery is fully charged before you start.

You should also avoid sticking the brush inside the body cavity. Hold the camera upside down (with the lens mount facing downwards) and squeeze the blower, directing jets of air onto the sensor.

Depending on the degree of the problem, this might be all you need to do.

In the case of my Canon EOS 20D, which managed to get fairly grubby before I noticed the problem, I tried the blower method four times – each time shooting a patch of blue sky to check the results, but it made not a jot of difference.

Scrub it off
For those stubborn, hard-to-remove particles, you’ll need something more aggressive than a puff of air, but obviously you don’t want to run the risk of causing any damage.

You wouldn’t expect to find too many companies prepared to guarantee that their products won’t damage your sensor, but one such is Photographic Solutions. Its Sensor Swabs are recommended by Kodak, Fujifilm and Leica.

The swab is a sensor-sized spatula (they are specifically designed for different camera models), manufactured in a clean room with a lint-free tissue pad covering the end.

You apply a couple of drops of Eclipse fluid, a methanol-based residue-free cleaning solution, to the end of the swab and wipe it across the sensor first using one side of the swab, then the other.

My first effort with Sensor Swabs resulted in little improvement, with my test image revealing about the same level of contamination as was present prior to cleaning. I repeated the process with a second clean swab, and this time things got worse.

In addition to the familiar light-grey, slightly translucent dust spots, a horrible black mark had also appeared. Had I scratched the sensor? There was nothing for it but to try again. This time I only used one side of the swab, sweeping the sensor from left to right, and things started to improve.

Many of the dust spots were gone, but the worrying black mark was still there. A fourth single-stroke swab did the trick, removing the black mark and the remaining dust spots.

I got my Sensor Swabs and Eclipse solution from Warehouse Express. At £35.95 for a pack of 12, plus £7.99 for the Eclipse fluid, it’s not a cheap solution (pun intended this time, sorry), but it works and, from my experience at least, appears to be safe.

Send it off
At this point it’s worth mentioning that attempting to clean your camera’s sensor could invalidate the warranty.

The blower method is the one recommended by Canon and, if you carry it out according to the instructions in the manual, you shouldn’t have anything to worry about.

Whatever the manufacturer and model of your camera, if the worst should happen and you damage the sensor, the most likely outcome is that you’ll be faced with a hefty repair bill.

If the prospect of poking about with swabs and blower brushes fills you with dread, but you still want to get rid of the dust, you should contact the manufacturer’s service department and ask them to do it for you. It won’t be cheap, but at least you don’t have the worry of ending up with a bigger problem than you started with.

Software solutions
If all else fails, or the dust spots are already on your images and it’s too late to do anything about it, you can always retouch them out. Don’t worry if your retouching skills are a little rusty, or even non-existent, there are automatic tools that will do the job and manual retouching of dust spots is not all that demanding.

Canon’s Digital Photo Professional application, which ships with most Canon digital SLRs, includes the same Fare (Film Automatic Retouching and Enhancement) technology used in Canon’s flatbed scanners. Fare automatically retouches dust spots and other marks and blemishes.

Nikon’s Capture 4 Raw image-processing application uses a reference image to identify and map the location of dust spots on the sensor and then automatically retouches them out.

Retouching
For light dust contamination – just the odd spot here and there – I’ve found that manual retouching is the most effective solution. Even if you have a lot of images you won’t need to retouch them all and, once you’ve done one, you’ll know exactly where to look.

You can do this in any image-editing application that has a clone tool.

Layer support is also useful. I will briefly describe how I do it in Photoshop, but you should not have any problem adapting the technique if you use another application.

Start by creating a new layer and calling it ‘retouch’. Select the Clone tool and pick a brush that is about twice the size of the dust spots with a very soft edge – in Photoshop use 0% hardness.

Check the Aligned and ‘Sample All Layers’ boxes in the tool options bar. This ensures that the pixels from the background layer are copied into the retouching layer. If your image editor can’t do this, just copy the background layer to create the retouching layer.

Sample an area close to the dust spot that is similar in tone and colour. For skies this will usually be to the right or left of the spot rather than above or below it. Then just click the spot to remove it. If there is a visible mark where you have cloned, choose Undo, resample from a different area and try again.

Most of the time it will work first time. For troublesome spots you may need to alter the brush size and hardness, sample a different area or alter the opacity. Changing the blend mode to lighten can also be helpful. If things really get messed up because the cloning is on a separate layer, it is easy to erase and start again.

Dust dos and don’ts
1. Prevent dust entering the camera. Use (clean) lens back caps and camera body caps, and keep the time the lens is off the camera to a minimum.

2. Switch off the camera before changing lenses (some cameras automatically switch off the sensor when you remove the lens).

3. Hold the camera with the sensor facing downwards when changing lenses.

4. Send your camera to the manufacturer to be cleaned professionally if you don’t feel confident about doing it yourself.

5. Don’t put body caps and lens caps in your pocket.

6. Don’t use a blower brush to brush dust off the sensor.

7. Don’t use compressed air products to blow dust off the sensor. The propellant leaves a residue which will smear the sensor and gunk up your camera.

8. Don’t insert a blower into the body. If the battery fails, the shutter and mirror will close on it, probably causing expensive-to-repair damage.

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