I have the Canon 5D Mark I and Mark II, and have read just about everything in here and on the web about Sensor cleaning, yet am having a horrible time with keeping my sensor clean enough to not have welded on spots that are visible when I shoot with the aperture stopped up to increase depth of field. I often shoot at 16 or higher. I shoot full time, and run my own photography business in the Seattle area. I have tried eclipse fluid and sensor swabs, but that actually makes the problem worse, as noticeable residue streaking is left behind that is also just as noticeable. I have tried the Dust Aid system, which works well for loose dust particles, but it has no effect on the welded on "dark circles" that appear on the sensor. I also have a rocket blower which can work for the loose particles too, but doesn't help with the welded on dark spots either. I'm assuming that these are micro water spots that adhere to the sensor and accumulate from moisture in the air?, but I'm not sure. I live in Seattle, and it is often pretty humid here, especially in the winter months. I am extremely careful about how I handle and store my cameras and lenses, and only keep them in closed a camera bag when not in use, and I only change lenses when it is necessary. When changing lenses, I always point the camera downwards, to minimize dust going into the sensor, and I make the lens change as fast as possible. The camera body is NEVER left without either a lens or a body cap on it. I have also tried the speckgrabber system, and that doesn't seem to do much either. Yesterday I took my 1 month old 5D Mark II into a very reputable camera store to have the sensor cleaned, since my attempt to clean several welded on spots with Eclipse fluid and sensor swabs only made it worse, didn't remove the spots, and created nasty streaks of residue on the sensor. They usually do a great job, and I can often go 6 months to a year before a I need another cleaning. Yesterday after driving 20 miles, and 60.00 later they cleaned the sensor extremely well, except for when I got it home, put on a lens and tried out a test shot, there was already one welded on spot in the center ! My guess is they missed it, but it may have naturally gone onto the sensor. The body cap was on the whole time from when they cleaned it too. I would like to be able to clean my own sensors well enough to get these welded on spots removed, but so far have been unable to find out how to do it effectively, since the eclipse fluid method does not work, and I would highly recommend that you DO NOT use it on your sensors.... I would like to know if anyone here has experienced similar problems, and how you have overcome them without having to pay a technician 60 dollars each and everytime you want to remove these welded on sensor spots. Does anyone clean their sensors effectively on their own, and if so, what are you using, and how do you do it? Any help or info would be much appreciated.