I had dust on the low-pass filter twice, they appear as black smudges on the photo.   I have a nikon d70s...  In Nikon's little book, they say when this happens, send it to a professional, but it's not that hard to clean up yourself most of the time...  You must just be extremely careful to not touch anything inside the camera.  I don't know about other cameras, but on the Nikon D70s, in the set up menu you can lock up the mirror.  When that's locked up, hold the camera face down and with a little blower bulb ( not the ones with a brush at the end cause the brush may contain dust that you'd be blowing inside the camera, besides it's harder to make sure the brush don't touch anything...) puff gently some air inside being very careful to not touch anything inside the camera with the bulb.  Don't use canned air either cause those can leave stuff too.   This took 2 minutes to do and was enough to get rid of those black spots on my photos, if they had still been there after that though, then I would have sent it to a specialist.  Now if you decide to try that and you screw up, don't hold me responsible...  ;)

Lucie
finfond.net
finfond.net (store)