Keeping Dust at Bay
Cameras featuring systems to control dust use an array of mechanisms to keepl dust from the image sensor (featuring electromagnetic fields) at bay and to clean the sensor automatically every time the camera is turned on (typically by vibrating the image sensor as a way to "shake off" dust particles). Each time you change lenses a chance occurs that dust may get into the body of the camera and remain on the sensor. Even when using utmost care when switching lenses, the mechanical components such as the quick-return mirror or shutter could still generate dust particles because of friction taking place during such movement. In addition, these components create air movement inside the body of the camera being enough to flurry those minuscule dust particles about. ✓
These issues are not nearly as critical inside SLR film cameras as the dust vanishes when the film inside is wound , however with DSLRs the sensor continues to remain in the same position. Even when dust particles are no larger than 0.1 mm (100 micrometres) which are the human eye cannot see, once they settle on the surface of the image sensor they can demean the quality of every image shot thereafter. In addition, it is typically it is difficult to eradicate the dust, many times requiring camera to be sent in for servicing.
Two types of dust
There are typically two main dust types that have the potential to degrade your image quality: Particles of dust which stick using electric force and particles of ssust that stick with intermolecular force.
1. Dust particles which stick through electrostatic charges. Much of the dust contamination adhering to the surface of the sensor is created by dust fragments as tiny as a single micrometre (0.001 mm) attaching by electrical charges. These fragments themselves contain a positive static electrical charge, as the sensor is charged negatively, which gives them attraction one another. This identical phenomenon can be seen on the screens of CRT and LCD monitors.
2. Dust particles attaching through intermolecular force This intermolecular force is not as strong as electrostatic charges. Although, it still is a magnet for microscopic-sized dust fragments attaching the image sensor using infinitesimal force. Although earthing (grounding) your camera can help diminish the issues with electrostatic dust it doesn't cut down intermolecular attraction. If, for instance, flour was sprinkled into your camera, it would nevertheless stick to the metal surface which is earthed. This type of dust is drawn using intermolecular force. Also liquid adheres to the sensor using intermolecular force and these molecules strongly adhere because of their ability to move in closer to an adhesion surface, causing it to be more difficult to completely remove this type contamination using a dust reduction system. In these instances, wiping down the optical elements with cleaning fluid which are at the front of the sensor may be necessary.
Beginnings of dust reduction systems
The first manufacturer to include system for reducing dust on a DSLR was Olympus, with the Supersonic Wave Filter (SSWF) system for reducing dust featured in 2003 on their Olympus E-1. All Olympus DSLRs subsequently have included this dust reduction system, along with Panasonic and Leica DSLRs; both companies employ the Olympus technology.
Prior to that Sigma sealed their camera mirror box using a protective filter placed at the back of the lens mount, keeping dust from getting into the camera body.
Other camera manufacturers, such as Sony in (2006), Canon in (2006), Pentax (2006), followed by Nikon in (2007), featuring their own technologies for removing dust. Each manufacturer employs a somewhat different technology.