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Keeping dust and other forms of atmospheric detritus off your camera’s imaging sensor has been one of life’s challenges since the inception of digital imaging. With more mirror-less Four Third and Micro Four Third cameras coming to market, dust issues are undoubtedly going to become even bigger issues for many shooters upgrading to interchangeable lens cameras.
And while most cameras nowadays contain dust-reduction systems that - in theory but not necessarily in practice – ‘shake’ errant dust bunnies off your sensor every time you power up and power down, there are several defensive moves you should take when swapping lenses in environments containing any measure of air, dust, and/or wind. In other words… anywhere… and more-so if the wind is blowing.
The thing about dust is that it's everywhere and has a habit of finding its way anywhere, and particularly in places you don't really want dust to go... like the surface of your imaging sensor. There are however, several easy precautions you can take that can save you hours of post-capture retouching time.
Two primary laws of nature you have to contend with when combating airborn particles are gravity and wind. The first one - gravity - is realatively easy to deal with because the rules of gravity are simple - if something becomes airborn it will ultimately settle back down to earth. Thus if your camera is lens-less and facing upwards, there's the near certainty that whatever's floating about will settle on your imaging sensor. So rule number one is always aim your camera downward when swapping lenses. Assuming you are not swapping lenses in a windy envirnment, dust travels downward, not upward. And do keep in mind the longer you keep the innards of your camera exposed the more likely you are going to get some kind of airborn schmutz within landing distance of your imaging sensor.
The best way to deal with wind - assuming you don't have the option of ducking indoors to swap optics - is to turn your back to the wind as you switch lenses. By turning your back - or better yet - ducking behind a wall, car, a large rock, or anything else that can keep you covered while you swap lenses; you lower the risk of having dust invade your lens chamber.
And when shooting in damp, rainy, dusty environments, or anywhere within salt-sniffing proximity to the beach, make sure to take extra care in this regard.Two additional tips for keeping your camera sensor dust-free are a) power-down your camera before changing lenses in order to reduce the dust-attracting qualities of static electricity; and b) have your lenses (and their respective front and rear caps) ready to go in order to minimize the amount of time the sensor is exposed to the elements.
In the next 'Rules of Thumb' we'll discuss the best ways to clean dust off your camera sensor when these dirty little particles find their way past good lens-swapping habits and in-camera dust-reduction systems.