Nikon D780 Reference Manual page 876

D
Use a Reliable Power Source
The shutter curtain is delicate and easily damaged. If the camera powers
off while the mirror is raised, the curtain will close automatically. To
prevent damage to the curtain caused by the shutter closing
inadvertently during the operation, observe the following precautions:
•
Do not turn the camera off while the mirror is raised.
•
Do not remove or disconnect the power source while the mirror is
raised.
•
If the battery runs low while the mirror is raised, a beep will sound and
the self-timer lamp will flash. The shutter curtain will close and the
mirror will be lowered after about two minutes; end cleaning or
inspection immediately.
D
Foreign Matter on the Low-Pass Filter
Foreign matter entering the camera when lenses or body caps are
removed or exchanged (or in rare circumstances lubricant or fine particles
from the camera itself) may adhere to the low-pass filter, where it may
appear in photographs taken under certain conditions. To prevent entry
of foreign matter when attaching the body cap or exchanging lenses,
avoid dusty environments and be sure to remove all dust and other
foreign matter that may be adhering to the camera mount, lens mount, or
body cap. To protect the camera when no lens is in place, be sure to
replace the supplied body cap. Should you encounter foreign matter that
cannot be removed using the image sensor cleaning option ( 0 823),
clean the low-pass filter as described in "Manual Cleaning" ( 0 827), or
have the filter cleaned by authorized Nikon service personnel.
Photographs affected by the presence of foreign matter on the sensor can
be retouched using the clean image options available in some imaging
applications.
830 Technical Notes