How to keep dust from the sensor in your DSLR
Camera care and maintenance is definitely an area where we all need to pay attention. With Digital SLR's as opposed to film, it is essential that we keep the inner workings as clean as possible.
Updated July 2021: Every time you change lenses, no matter how careful you are, you may let dust in. A minute rush of air as you pull the lens away from the body is enough to make that happen.
The dust will first reach the mirror and internal cavity of the camera, but not the sensor at this point. When you take a photo, the shutter opens allowing any particles to now enter the sensor area.
If this dust, big or small, lands on your sensor, it will show up in your photos at some point. Dust appears more when using small apertures (f11, f16) and it uniform areas such as a clear sky.
The dust "situation" above happened when I used a sweaty blower brush on the sensor. The brush had been kept in a hot camera bag in Spain leading to a build up of droplets inside. A quick blast or two whilst attempting to clean the sensor made the situation a LOT worse!
Built-In Sensor Cleaning
Most modern DSLR's have an internal sensor cleaning mechanism which vibrates the sensor to try and clear the dust. This normally gets applied every time you turn the camera on or off. If it works, the dust is still inside...lurking and waiting to attach itself to the sensor once more.
You need to keep on top of it through regular camera care and maintenance.
With film, it was easy. The emulsion of the film was kept in an "air tight" canister until safely inside the camera and at the point of exposure there was nothing but air between the film and lens.
The film was only exposed to dust for a few shots before it was wound back into the canister. Even then, there was cloth around the slit so it cleaned the film as it left and re-entered the canister.
As long as the lens was spotless, you were ok.
Nowadays, with expensive sensors, it is imperative that the interior is kept clean (unless you really enjoy post processing). Not only do you have the sensor itself, but a "low pass" filter in front of that too! If you take time out to take care of your kit it should last for a long time and you will save hours or spot removing in Photoshop etc.
How to prevent dust entering your camera
Start by changing lenses in a dust free environment. If you can't find one, invest in a changing bag for when you are on location or outside.
Next, become quicker at changing lenses and don't leave your camera "open" for too long with no lens attached.
Similarly, ensure the rear elements of your lens are also dust free before putting on the camera. After all, if you add a dusty lens to the camera body, you are asking for trouble.
If you do notice dust on the lens, get yourself a sensor cleaning kit. In fact, get one anyway, you will need to learn to use one at some point anyway. I always have one handy for emergencies (wedding photography for example).
For more information on keeping your camera clean inside and out, go to: Camera Cleaning and Maintenance
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