Nikon D300s - Manual (Page 136)

110
Z
3
Frame a photograph, focus, and shoot.
A Non-CPU Lenses (0 342)
Use the lens aperture ring to adjust aperture.
If the maximum aperture of the lens has been
specified using the
Non-CPU lens data item
in setup menu ( 0 196) when a non-CPU lens is
attached, the current f-number will be
displayed in the viewfinder and control panel,
rounded to the nearest full stop. Otherwise
the aperture displays will show only the number of stops (
F, with
maximum aperture displayed as FA) and the f-number must be read
from the lens aperture ring.