Digital SLR Cleaning Methods
Cleaning the Mirror and Focussing Screen
The mirror is easily cleaned, as it is immediately visible when the lens is removed. Because the mirror is semi-silvered, it should be treated with utmost care. You should only clean when absolutely necessary, as minor dust marks will have no effect on the viewfinder image.
The focussing screen is situated directly above the mirror. Contamination here is most likely going to visible in the viewfinder. As the screen is usually soft plastic it is easily scratched so it needs to be cleaned with care. If you can see the dust particles, you can use a SpeckGrabber to carefully pull them off the screen. You may also try a small antistatic brush to remove dust. Finally, if necessary, you may gently wet clean the screen with a Sensor Swab and some Eclipse fluid. Bend the swab 90º at the end to make it easier to clean into the corners.
Cleaning the focussing screen
Sometimes dust can make it’s way onto the ‘wrong’ side of the focussing screen. If this happens, no amount of cleaning the accessible side will remove it. The screen will have to be taken out of the camera to allow both sides to be cleaned. Removal of the screen is quite fiddly and is beyond the scope of this guide. We recommend that in this situation the camera should be cleaned professionally.