How to prevent dust, dirt or moisture from getting on the image sensor (or mirror) inside the camera

Even with regular cleaning of the image sensor or mirror, since DSLR, SLT, NEX, and ILCE cameras use interchangeable lenses, there is always the possibility that a piece of dust, spec of dirt, or moisture may find its way inside your camera and ultimately onto the image sensor (or mirror) when changing lenses. There are precautions, however, to help avoid this situation.

• Turn off the camera before changing the lens - image sensors can have an electric charge that attracts dust.
• Only change lenses in a clean environment, preferably indoors, away from fans, vents, or windows.
• Check the lens before attaching it to the camera; if dust is found on the lens, a blower can be used to remove it.
• Have the lens you want to attach ready beforehand so the camera's lens opening is exposed for as little time as possible.
• Position the camera downward when removing and attaching a lens to prevent dust or dirt from falling into the lens opening.
• Attach a dust cap to the front of the camera after removing the lens if not using the camera for a prolonged amount of time.
• Attach a dust cap to the lens you removed from the camera.

As stated previously, there is still a chance of dust, dirt, or moisture finding its way inside a camera with interchangeable lenses. In addition, moisture may still accumulate if the air inside the camera is dry and the air in the outside environment is moist. Following the guidelines above, however, should help minimize these circumstances.