Hands on: Keep your camera sensor speck-free

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.