text: I had camera cleaned because of black dots and fiber pieces on the focusing screen. It was fine until I changed lens. After changing lens I found more black particles on focus screen.I had checked the lens befor pitting it on and it was clean. The black particles have to be comming from something in the camera when I change lens. any suggestions.
  How do you clean the dust out of the projector, there are particles that look like small white stars on the black areas and black stars on the white areas. Is this dust?
  If you focus the image on a screen up close to the projector and notice small rectangular black and white spots, then you have pixel failures.
  go through the color options and check if some pixels are permanently on or off (ie small dots or black) instead of a uniform colour on the screen.
  It is possible you are trying to focus on somethind that is either completly white or completely black. It has trouble focusing in the dark as well. make sure your auto focus point (The red dots in your view finder is in the centre. you can move the red dot with the button on top of your camera that looks like 4 squares. simply look through your viewfinder push the shutter button down half way and the red dot should flash. if it isn't in the centre then move it with the button on top (4 squares) and try again until you get it in the centre.
  Please...do not touch the mirror!!! The black dot is dust on the sensor. Google the words...digital camera sensor cleaning. You will get complete directions and where to buy the supplies.