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Digital SLR Cleaning Methods
When to clean the sensor
The question we get asked the most, is ‘How often should I clean my sensor?’
This is a an impossible question to answer as it depends on where the camera has been used, how many times the lens is changed, how clean the camera and lens are kept and so on. Mostly though it depends on each users tolerance for dust spots on their images. Since dust spots usually have to be retouched on the computer, a good measure to use is how much time you are spending retouching these spots. Clearly one or two spots on an image are easy to cope with, but when you have to remove twenty or more, it maybe time to consider a sensor clean!
It's also worth pointing out that it is easy to become a little bit obsessed with cleaning, wanting to clean the sensor every time a new spot appears. Try to resist this and only clean when the number of dust spots has reached your personal tolerance limit. It’s a fact of life that dust is all around and if you clean today, there will be a fresh dust mark back in a few days. So, manage the dust issue rather than striving to maintain a 100% clean sensor at all times.