Nikon D6 Reference Manual page 424

A
Close-ups
Because focus depth is reduced at short focus distances, we recommend
choosing smaller focus steps and increasing the number of shots when
photographing subjects close to the camera.
A
During Shooting
During focus shift photography, the Q icon
will flash in the top control panel. Immediately
before each shot, the AF indicator will flash and
the shutter speed display will show the
number of shots remaining.
372
Varying Focus over a Series of Photos (Focus Shift Shooting)