After an extended period of use with various lens changing, every DSLR owner will notice that dirt has accumulated on the camera sensor. Each mirror slap and shutter operation can produce wear. Even without changing lenses, fine dust particles can enter the camera since the inside of a DSLR camera is not airtight and zooming pumps air out of the body or sucks air back into the mirror chamber. Today almost every DSLR has a built-in sensor cleaning function based on micro-vibrations to shake off dirt from the sensor surface. However the effect is very limited and sticky particles like pollen will still remain. Photographers that mainly shoot on wide apertures will most probably never notice smaller spots of dirt. But every landscape photographer who sometimes shoots at f/16 or f/22 will be displeased about many spots in the images and a sensor cleaning needs to be performed at some point.
Usually camera sensors are cleaned with special soft wipers. Partially impregnated with alcohol or cleaning liquids, this method is often reported to push the dirt more into the corners of the sensor then to remove it completely. When i needed to clean my sensor for the first time i decided to take Nikons check & clean service. The result was below my expectations and i still found some very small spots in my images.
While searching the internet i found the method of sensor cleaning with sensor film. At the same time a friend of mine told me that he recently performed a cleaning and was really convinced by the results. Sensor film is a viscous polymer solution that is painted on the sensor surface. The polymer dries while forming a film that binds all dirt and can be fully removed at one piece. See how it works this video of the manufacturer.
Without doubt a very difficult procedure but I just tried it. After the film completely dried I was faced with the problem that is often discussed in various Internet forums. The paper strap for removing the film from the sensor broke three times. I was a bit perplexed and left the camera as it was over night. The next day I made another attempt and took a strap of packaging paper that seemed to be much stronger than the originally supplied paper. The film draw off completely. The cause of the initial problems might have been the high humidity on the day of cleaning. Presumably the film was not dry enough and the slightly higher adhesion made the separation from the sensor impossible. It also seems to me that packaging paper is much stronger for removing the film.
With the result of the cleaning procedure I am ultimately excited. The film could be drawn off completely without leaving any residual polymer. On a test image I could not identify any single point of dirt. One must be very careful using this method because working in the mirror chamber requires concentration and a steady hand. With practice however it is very easy to carry out and the result is really 100%. Therefore sensor film is my clear recommendation and I will continue to apply when it is necessary.
Finally, I have a recommendation for users of Nikon D800and D600: once the cleaning mode is activated, the mirror is flipped away and the shutter is open, you should remove the battery from the camera without switching it off. The cleaning mode will remain active and you do not need to worry that the shutter closes. If this works the same way on other camera bodies needs to be checked prior to cleaning.
After a couple of cleanings performed (Nikon D800/E and D600) I am now using a piece of cloth instead of paper for removing the film from the sensor. The advantage is quite simple: a fiber cloth is much more resistant to tearing than paper. You can use cloth washing labels that are sewn into each garment . These are usually made of synthetic fibers, very thin yet extremely stable. You just have to make sure that it is cloth, not tissue foil. Best practice is to cut a 3mm wide strip and fold at one end an approx. 3x3mm large area with hard edge. Place this area with the hard folded edge as shown on the 2nd image in the far corner of the sensor. It is important that you place the folded edge as far as possible to the edge of the coated sensor area. This will help to remove the dried sensorfilm without any problems.