Almost anyone who has owned an EOS digital camera for some time will be accustomed to seeing dust spots on their photos. A few dust spots are little more than a nuisance, and can be easily cloned out in image editing software. At some point though, as the dust spots increase, the question of sensor cleaning arises. That is, how to do it, and more pertinently, how to do it without ruining the camera’s sensor.

‘Sensor cleaning’ is a commonly used but inaccurate phrase. The sensor is covered by a low-pass filter and any dust is on the filter, not the sensor. We still don’t want to damage it, but it’s reassuring to know that cleaning equipment will never touch the sensor itself.

Above The EOS 50D self-cleaning sensor unit

Why does the problem exist in the first place? The problem is not new to digital cameras. Dust also enters film camera bodies, but the surface on which the dust settles, the film emulsion, moves on when the film is advanced. It’s like taking every photo with a brand new clean sensor.

In digital cameras, the sensor stays in one place and if dust isn’t removed, it builds up. Canon’s Integrated Cleaning System, introduced on the EOS 400D in 2006, helps to reduce the problem by vibrating the filter every time you switch the camera on. However, even this doesn’t eliminate all dust, and inevitably any EOS will need its sensor filter cleaned at some point.

The answer to the question of whether or not the sensor needs cleaning depends not just on how much dust there is, but whether it’s visible in your images.

It is possible that there is dust on your camera’s sensor filter, but it cannot be detected in your photos. The images below were all taken with the same EOS 350D camera, which at the time that these images were taken had never had its sensor filter cleaned. The first photo has lots of blue sky and, upon close examination, a considerable amount of dust spots. The second photo only has a little blue sky and the dust spots are less visible. This is because the dust spots are only visible against the paler sky. Any dust spots over the water and rocks are hidden by the textures in the image.

Cleaning your sensor

Canon only recommends two sensor filter cleaning solutions. The first is to use an air blower bulb to clear dust, and the second is to send your camera to a Canon Service Centre.

Canon’s main fear is the shutter closing during the cleaning process, which can badly damage the internal workings of the camera, leading to an expensive repair bill.

Stage one: cleaning with a blower

Regularly using an air blower to remove loose dust from the sensor filter is a simple dust management procedure. It is a non-invasive procedure as the air blower never comes close to the sensor filter, so there is no risk of physical damage.

The only danger from using an air blower bulb is that dust may collect inside the blower and you could inadvertently blow this onto the sensor filter. To avoid this, before using to blow dust off the sensor filter, point the blower away from the camera and squeeze hard several times to eject any dust that is inside.

It helps if the blower is stored in a clean environment. Keep it inside a sealable ziplock plastic bag so that dust (from the bottom of your camera bag, for example) does not get inside the blower.

The best type of blower bulb to use is one made from silicone. This material degrades more slowly than rubber, reducing the risk of dust forming inside the bulb.

Do not use cans of compressed air for cleaning the inside of your camera. The air-jet is often very powerful and can damage delicate mechanisms if used to close. Also, some compressed air can used an inert propellant and this can condense onto the sensor to leave marks – the very thing you are trying to avoid!

Cleaning with a blower bulb

1 Select the sensor cleaning option in the camera menu. This raises the camera mirror and opens the shutter.

2 Point the blower away from the camera and squeeze hard to expel any dust inside.

3 Hold the camera body upside down and point the blower at the sensor filter. Make sure the point of the air blower doesn't reach past the lens mount Squeeze once to expel air to remove loose dust.

4 Turn the camera off; this will automatically close the shutter and lower the mirror so that the camera is ready for use when you turn it back on.

Next page for more cleaning techniques >>

Sensor cleaning

If you can see dust spots on your digital images, then it’s time to have your camera’s sensor cleaned professionally. Or you can do it yourself. We guide you through safe cleaning techniques, and how to tell when your sensor needs cleaning.

Camera compatibility: All EOS cameras

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