Nikon D6 Reference Manual page 1127

The Low-Pass Filter
Dirt or dust entering the camera when lenses are exchanged or
the body cap is removed may adhere to the low-pass filter and
affect your photographs. The "clean image sensor" option
vibrates the filter to remove dust.
The filter can be cleaned at any time from the menus, or
cleaning can be performed automatically when the camera is
turned on or off.
❚❚ Using the Menus
•
For maximum effect, hold the camera
in normal orientation (base down).
•
Select [Clean image sensor] in the
setup menu, then highlight [Clean
now] and press J to begin cleaning.
•
Camera controls cannot be used while cleaning is in progress.
Do not remove or disconnect the power source.
•
The setup menu will be displayed when cleaning is complete.
Caring for the Camera
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