Nikon D780 Reference Manual page 722

•
" F " will appear in the viewfinder and control panel
displays.
•
To exit without acquiring Image Dust Off reference data,
press G .
2
With the lens about ten centimeters (four inches)
from a well-lit, featureless white object, frame the
object so that it fills the display and then press the
shutter-release button halfway.
•
In autofocus mode, focus will automatically be set to
infinity.
•
In manual focus mode, set focus to infinity manually.
676 Menu Guide > B The Setup Menu