Arnoud Quanjer Wildlife Photography

One of the most irritating things about a digital SLR is the fact that dust can get stuck to the sensor. This dust will be visible on your pictures as UFO shaped objects called 'dustbunnies'. The name dustbunnies comes from little clumps of fluff that form under furniture and in corners that are not cleaned regularly. They are made of hair, lint, dead skin, dust, and sometimes light rubbish and debris, and are held together by static electricity and entanglement. Dust bunnies are frequently a source of amusement by making out that they are actual living creatures formed of dust, attested to by the many websites on the care and feeding of dust bunnies. In digital photography these dustbunnies are little, even microscopic, specs of dust that cling to the sensor and they cause frustration rather than amusement. No matter what you do, eventually dust will get into your camera and it will find its way to your sensor. The dust gets into the camera when you change lenses, it is factory delivered (Canon has a bad rep with this, lots of cameras are delivered with dirty sensors) and you can get dust into the camera by using zoom lenses that suckin air when you change the focal length of the lens. As soon as you accept the fact that dust will eventually get into your camera the next step is to find a way to remove the dust from the sensor.

Preventing dust from getting into your camera

There isn't a full proof way to prevent dust getting into the camera, but there are a number of precautions that you can take that will minimise the amount of dust that will find its way into your camera. The most important precaution you can take is to turn off the camera while you change lenses. When your camera is on the sensor will have an electrical charge that will attract dust. Turning the camera off kills the electrical charge. As dust falls down and not up due to gravity make sure that you point the camera down while changing lenses. There are more precautions that you can take that fall in the no-brainers category like not changing lenses in dusty and windy places, but out in the field the first two precautions are the most important.

Checking for dust

The easiest way to check for dust on your sensor is to switch your camera to manual focus, selecting the smallest possible aperture (=the highest number eg f/22) and taking a picture of a piece of blue sky. Don't worry about focussing or holding the camera still, that's irrelevant for checking for dust. At the smallest aperture the dust specs will become instantly visible if you shoot a blue sky. The dust specs will look like UFO's in the sky. If you have dust specs on the sensor then the next step is removing the dust...

Cleaning the sensor

Most manufacturers will tell you that you're not allowed to clean the sensor yourself. According to these companies you should bring your camera to a repair centre and let them do the cleaning for you. They in fact sometimes even state that by cleaning the sensor yourself you'll void your warranty. If I was a manufacturer then I'd probably say the same thing, repair centres make a lot of money cleaning sensors. The reality is that cleaning a sensor is very easy, totally safe and very cheap to do yourself as long as you follow some basic guidelines. I usually clean my sensors once every two or three days when I'm in Africa. I feel that it's easier to clean the sensors regularly than to spend endless hours cloning all these specs out in Adobe Photoshop.

• The first step in cleaning a sensor is to find the option on your camera that flips up the camera mirror. Contrary to what some people believe the sensor is not directly exposed in a DSLR, it is hidden by the cameras mirror. Once the mirror flips up you'll be able to see the sensor. Most DSLRs offer a menu option that will flip the mirror up. On Canon cameras this menu is called 'Clean sensor'. One of the most important things to do when you're going to clean your sensor is to make sure that you use a fully loaded battery! Don't take chances with semi-full batteries! When you start to clean the sensor you have to flip up the mirror. Keeping the mirror flipped up takes power, should the battery go flat then the mirror will flip down again. If you're cleaning the sensor and are obstructing the mirror while it flips down unexpectedly then you will probably damage the mirror!
• After you've made sure that you're using a fresh battery flip up the mirror and gently blow air over the sensor to remove dust specs. Hold the camera upside down while doing this so the dust falls down instead of blowing it to other areas of your camera. Make sure that you don't use pressurised air as that they can contain liquid propellants that can gunk-up the sensor, which will then require professional cleaning or replacement. Also don't blow into the camera yourself as your breath will contain moisture which will 'glue' any dust firmly to the sensor. Use either a hand squeezed blower bulb or compressed CO2 gas and nothing else and don't hit the sensor with the blower bulb! 
• If blowing air on the sensor doesn't remove the dust then you have to resort to more drastic methods. There are a number of products on the market that you can use to clean sensors. The method I use is known on the Internet as the 'Copperhill method'. For this method you need a bottle of Eclipse fluid and either pec-pad wipes or a SensorSwab. The way it works is you remove a swab from its sealed pouch and place a couple of drops of Eclipse fluid on the pad. Starting at one side of the sensor glass gently but firmly wipe across the glass from one side to the other. Only lift the pad once you reach the far side. Never use a swipe twice!

See http://www.pbase.com/copperhill/ccd_cleaning for detailed instructions on how to clean sensors. You'll also find information on how to purchase cleaning kits there.