There are a few places where dust and grime tend to accumulate in a camera's optical system that require a little extra effort to keep clean. They include the rear element, filter wheel and prism block. Cleaning these hidden optical surfaces, while a simple matter on most professional video cameras, is a job that should be left to a factory-authorized service center on any camera that does not have a removable lens.
To safely remove the lens, place your camera on a flat work surface, unplug the control cable, and loosen the locking collar by firmly gripping it--with both hands if necessary--and applying enough torque to start it turning in a counterclockwise direction. Stop turning as soon as the locking collar begins to rotate and reposition your hands so the left hand supports the lens. Now rotate the collar until it stops and remove the lens from the mount by drawing it away from the camera.
Inspect the rear element of the lens for dust and fingerprints. Use a soft brush or a gentle puff of dry air to remove any dust particles. Hold the lens with the rear element facing down when cleaning so dislodged dust will float away and not simply relocate to another part of the lens. While the lens is off, rotate the camera's filter wheel and check each filter for cleanliness. A small flashlight is often helpful for highlighting dust particles. As with the lens, let gravity do the work as you take care not to brush or blow dust further into the camera.
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