Notes on DSLR Sensor Cleaning
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Revised April 2016
When I wrote this note in 2009, sensor dust was more of a problem than is the case with modern DSLRs. Advances, such as ultrasonic cleaning and fluoride coatings, usually do a good job of keeping the sensor free from dust. Hopefully, you will not need to use the techniques described in this note but I shall leave this information, in case it proves necessary.
Having just (May 2009) given my D70 sensor a spring clean, I thought I would share a few thoughts on the procedure.
Fig.1 - Sensor Cleaning Setup
Sooner or later, every DSLR owner is going to be faced with the problem of dust spots, epecially in the sky areas of photographs. Up to a point, they can most easily be dealt with by use of the clone tool in Photoshop but, eventually, it becomes a major irritation. In macro work, in particular, it becomes much more of a concern when a dust spot obscures an important detail!
Sensor cleaning is usually approached with some trepidation (which is justified) and often with fear (which is not). Firstly, I'll dispel a few myths:
When you clean the 'sensor', you are not actually touching the sensor at all. The silicon sensor chip is safely tucked away behind a thin glass filter and it is this glass suface which collects dust. So, the task is simply to clean some glass and it is not really that exotic at all! Of course, the glass is thin and you don't want to press on it very hard but, at the same time, it is not ridiculously fragile. On older cameras, such as the Nikon D100, the glass was very close to the sensor but newer cameras have a larger separation. The advantage of this greater separation is that very small specks of dust are rendered more 'out of focus', and are thus less intrusive on a photograph. In macro work, where very small apertures are used, they can still, however, become annoyingly visible.
Overall then, in my opinion, this is not a job to do every day but it is not so difficult or dangerous that it needs to be put off forever. If dust is spoiling your pics then I suggest you give it a try. Remember that your camera manufacturer may not approve and you may invalidate your Warranty.
Tools for the job
A blower brush (without the brush tip attached) and a mini vacuum cleaner are good for an initial removal of loose dust in the mirror box of the camera. You will need to find out how to raise the mirror, in your camera's instruction manual, and it is wise to make sure that the camera battery is fully charged (or use external power), in case the mirror suddenly drops unexpectedly.
After removing the lens, I use an illuminated magnifier to see inside the mirror box clearly - it often provides sufficient magnification for you to see specks of dust on the cover-glass over the sensor. I then use the blower, held in the lens mount opening, to dislodge any loose dust in the mirror box and, hopefully, from the cover-glass itself. Take care not to touch the cover-glass with the tip of the blower or mini-vac, as they will leave marks! The mini-vac ensures that loosened dust doesn't just fall back onto the internal surfaces. The camera makers say 'don't do it' but you can use a household vacuum cleaner at a reasonable distance to remove all dust from the working area - just don't get too close, or it may affect some delicate part of the mechanism.
Its worth checking at this stage whether the dust has been reduced to a level that you can live with. Take a photo of a blank sky with a small aperture (f/22 or smaller) and see if you are happy with the level of dust. Don't be too disheartened if there seems to be more dust than before you started - it does happen! You might want to have another close look and repeat the blowing and sucking, or overcome your trepidation and proceed to the next stage.
The next job is proper window cleaning and you need a spotless cleaning cloth! I use 'Digipads', which come in different sizes to fit the width of specific sensors. Each Digipad is in its own sealed plastic bag and should only be removed immediately before use. You then need to moisten (not 'wet') the pad with Eclipse fluid - which is very clean alcohol.
A 'Starter Kit' of five Digipads and a small bottle of Eclipse fluid (which should last for years, if you keep the bottle tightly closed) is available from Warehouse Express (in the UK).
Two drops of fluid are sufficient, but you must use the pad quickly as the alcohol soon evaporates. You will find that the Digipad is almost exactly the same width as the height of the cover-glass, so hold it firmly across one end of the sensor and wipe smoothly and steadily in a single sweep, holding the handle of the pad leaning forward into the stroke, to the opposite end of the glass, like a windscreen wiper. Then tilt the handle back towards the original end and sweep back to the start. If the sensor height is greater than the pad, move the stroke slightly, to ensure that the whole cover-glass is wiped. That's it - no more! If you use the same pad again, you are likely to return the dust back onto the sensor.
Fig.2 - Viewing the Sensor
Fig.3 - Making the Stroke
Drop the mirror and re-fit the lens and see how it looks, with a test photo of a blank sky. Hopefully, it will look pretty good - possibly, even, perfect!! Sometimes, you might see a few streaks or smears, which is almost certainly because you used too much fluid - more is NOT better. It will probably evaporate of its own accord in a few minutes, so is not of concern. If you are still not happy but feel that you have got the knack, then do it again - I had three goes the first time but now find I can do all that is necessary in a single shot.
Remember, it is at your own risk - only you can decide if the risk is worth taking.
İMike Flemming, May 2009
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