Question: There are spots on my images, especially at small apertures.
This is sensor dirt. All digital cameras with interchangeable lenses have this problem, but an M9 is particularly prone, because there is no mirror as extra barrier and the lack of an AA filter makes the dirt more visible.
One should prevent dust from entering the camera as much as possible. There are a number of strategies.
1. Avoid changing lenses more than necessary.
2. Change lenses in as much of a dust-free environment as possible
3. Keep the rear end of the lens as clean as possible
4. Change the lens with the camera mouth facing downwards
5. (This may be a myth) Switch off the camera before changing lenses.
But dust will come on the sensor anyway.
Consult the manual to find the sensor cleaning item in the menu and use a FULLY charged battery. Before opening the shutter blow out the camera (using a bulb blower, not compressed air or your mouth!) to dislodge any loose dust.
If the dust on the sensor is loose one can blow off the sensor using a good bulb blower, (Rocket Blower by Giotto for instance) with the camera mouth facing downwards.
If that does not clear the problem there are sensor brushes like the Arctic Butterfly by Visible Dust that are quite effective or the little vacuum cleaner by Green Clean. At this stage the use of a Sensor Loupe can be very helpful.
If spots on the sensor persist you are dealing with stuck dirt like pollen or oil spots and need to revert to wet cleaning. There are numerous threads on the subject. The Visible Dust products are highly recommended or the Green Clean wet-and-dry method.
Use a proper solvent for grease if you think you are dealing with oil etc. (Visible Dust Smear Away or Dust-Aid Sensor Clean (my preference)
Open the shutter for cleaning and blow it once again with a bulb blower or vacuum clean it, to remove any loose particles which might be dragged across the sensor and cause scratches.
Although the M9 is full frame and there are size 1 sensor swabs on the market, I prefer using the swabs for 1.3 sensors (and APS-C swabs for the M8)
Take a clean swab, put on three small drops of Sensor Cleaning Fluid and in two sweeps, top and bottow go to one side - do not over-press!!- and sweep back again, using the other side of the swab automatically.
Or, using the wet-and-dry system, swab with the wet sponge and dry with a couple of sweeps with the dry swab. Don't let the fluid spill over the edge of the sensor too much - there are electronic connections there.
That is all - close the shutter and test the camera by taking an unfocussed image of an evenly lit surface at the smallest aperture.
In the unlikely case it is needed, repeat.
There are other cleaning systems, such as stamping tools. I find them quite effective, as long as there are no greasy spots on the sensor.
Just stamp, don't rub. They are a bit scary as one pulls the cover glass. Leica Customer Service seem to be quite happy using them, so they should be safe.
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There are also sensor cleaning services or Leica Customer Service, but those are expensive and will keep the camera for a while. They may also not be readily available if one is travelling. Sensor cleaning is something any owner should be able to do himself.
If you are fairly certain your spots are oil or grease, it may be wise to omit the step with the Arctic Butterfly, as it may become contaminated by the grease. In case that happens it can be cleaned with the special fluid provided.
