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Monday, 19 June 2006 00:00

Sensor Cleaning

If you own a Digital SLR at some point you will look at your photos and wonder why there are little black spots in the same position on some of them. Often people think that it's a mark either on or inside their lenses - which it's possible it could be but if you have multiple lenses it's very easy to rule this out, whilst I've even heard of some people thinking that the sensor on their camera has been damaged and have sent it off for repair.

In 99% of these cases the cause of these black marks is simply dust on the sensor. Even if you don't currently have any marks on your photos there is still a very good chance that you have dust on your sensor too. To see if you have try this simple test.

  • Set your camera to aperture priority or manual and choose the smallest aperture you can, typically f/22.

  • Mount the camera on a tripod or other solid object

  • Place a white piece of card or paper in front of the camera (at a distance the camera can focus on, 1 meter away for example)

  • Focus on the card and take a photo

  • Now upload the photo to your computer and open it in your favourite image editor and zoom in to 100%

As you scroll around your photo you will probably notice little black 'splodges' and perhaps even the odd hair. This is dust on your sensor and needs to be removed. You may be wondering why either you haven't seen this before or why it only appears on some photos. This is due to the aperture you are using. Typically at large apertures f/4 or above dust isn't that visible because the depth of field created by that aperture is so shallow as to make dust so blurred that it becomes invisible. Smaller apertures however have a much greater depth of field and so more readily show up any dust which is why you may often see's specs in the sky on any landscape photographs you take.

If you do have dust on your sensor the main thing to realise is that it can be removed simply and by you. There does seem to be a lot of fear over cleaning your own sensor with a lot of scare stories supposedly of people who have scratched their sensors or otherwise damaged them. The truth, however, is a lot less scary and that is, as long as you follow a few obvious precautions and follow the guides to the various cleaning products it is highly unlikely that you will damage your camera at all.

But which cleaning system do you use? There does seem to be numerous different ways that people suggest to cleaning your sensor with varying degrees of success and varying degrees of risk in damaging your camera. I personally have read stories ranging from people using mini vacuum cleaners to specially shaped ice lolly sticks with a lint free cloth wrapped around it however all the different techniques are all based around three methods of dust removal. Dislodge by air, dislodge by liquid, dislodge by wiping. I have tried all three techniques and here is what I have found.

Giottos Rocket Air BlowerThe Giottos Rocket Air Blower produces a blast of air that is more powerful than most other air blowers that I have come across and has the advantage over cans of compressed air in that it does not use any liquid propellant or other chemicals and so is perfectly safe to use on your sensor. Can's of compressed air, even those that say they are propellant free should not be used as fine drops of moisture can still be sprayed onto your sensor which can leave marks.

In terms of cleaning, the Giottos Rocket Air Blower does a reasonable job as long as the dust isn't stuck to the sensor however I found that there were often more stubborn marks that the Rocket simply could not move at all. It's a good idea to have one of these in your bag, and at under £10 they are certainly affordable, but in my experience they are best used as a preventative measure instead of a cure. By this I mean that when I change lenses I tend to now use the Rocket to 'clean' the end of the lens before attaching it to the body. If you are going to use the Rocket to clean your sensor at any stage then one thing I would suggest is to turn your camera so that the lens mount faces down. This way any debris that is removed will hopefully fall out of the camera instead of being blasted further into the body. It should also be pointed out that although the Rocket is reasonably effective in removing dust from the mirror I personally feel that this is too risky as the angle of the mirror could deflect the burst of air and therefore any dust with it, further into the camera body. Another common complaint with all SLR's is dust inside the viewfinder, due to the design of all SLR cameras the Rocket is largely ineffective at removing this dust and their is an increased risk of blowing this dust onto the sensor anyway.

Sensor BrushAnother method is to use a sensor brush, which are a relatively new idea, and one that a lot of people rave about. There are a wide range of sensor brushes but all work in the same way where you have a brush whose bristles are completely uncoated and are made of nylon. A can of compressed air is then fired through the bristles for a few seconds to charge them with static electricity. When you then wipe the brush across the sensor the dust particles are attracted to the brush via the static.

In practice these brushes are very effective and the fact that the brushes are so soft and that you do not need to, nor should you ever, press down hard on the sensor, means that there is little chance of damaging your camera. The only thing that I have found with some of these brushes is that in one instance when I had to repeatedly use the brush to get rid of one stubborn mark, the brushes started to leave faint streaks across my sensor. These marks did not show up on my photos and I think were actually the result of a build up of propellant from the compressed air I was using. However these marks were quickly removed by using some eclipse fluid on a pec-pad (more on which in a minute) and no damage was made to the camera. Unlike the Rocker Blower as there is some physical contact between the brush and the dust these sensor brushes can remove most specs of dust however I did find that there were on or two that I still couldn't remove as quickly as I would have liked.

Sensor Swabs

Sensor Swabs are the final way of cleaning my sensor that I have used and are also my preferred and most successful method as well. There are a few types of sensor swabs available but the ones I use and recommend are made by Crown Digital.

The swabs themselves come in a few different sizes to match the size of your sensor and consist of a plastic applicator which is wrapped in a special lint free material. According to the Crown Digital website this material is not the same as the pec-pad material which can be used for cleaning lenses and other camera equipment but I have to admit that it looks the same to me and I know of several people who have wrapped a pec-pad around and old swab instead of buying new ones as they are so expensive (a pack of 12 swabs which should only be used once costs £35), and have not reported any problems in doing this although I have not tried this myself and so cannot recommend this practice. You cannot use the swabs on their own though, instead you have to buy a bottle of Eclipse Cleaning Fluid (1 bottle will last you years!) and apply 2 drops to the tip of the swab and then gently wipe the swab in one direction across your sensor, then turn the swab over and wipe back in the other direction. As mentioned before you are recommended to use a new swab after each wipe so as to not re-introduce any dirt back onto the sensor, however due to the extremely high price for each swab I, along with every other user I know of, re-use the same swab a few times during any single cleaning session. In other words I typically only use one swab each time I clean my camera.

Some people are nervous about applying a liquid to their sensor which is understandable however I have never experienced any problems with doing this and in fact have often found it the only way of removing all the dust from my sensor no matter how stuck on it may be.

Things to remember when cleaning your sensor.

  • Make sure your battery is fully charged

  • Don't use compressed air directly on your sensor

  • Don't try and clean your sensor or even change lenses in a dusty environment which include places like a beach of building site.

  • Don't press down hard on your sensor when using a brush or swab. Firm pressure is more than enough.

  • Don't rub the swab or brush across the sensor in a backwards and forwards motion. This is more likely to damage the filter that covers the sensor itself.

  • Don't use excessive amounts of any cleaning fluid on a sensor swab, one or two drops is ample.

  • Never use your fingers to remove any dust or hair from your sensor. Your skin has oils that will mark the sensor and your skin will also be very rough compared to a swab or brush and so could damage your camera.

  • Never blow into your camera as doing so will fire droplets of moisture onto your sensor

  • If in doubt don't do it and send your camera off to be cleaned.

Read 2242 times Last modified on Monday, 09 June 2014 21:42

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