Nikon N90 AF Instruction Manual page 66

66
With lenses having no CPU, F -
-
appears
instead of aperture value in LCD panel and
viewfinder.
With AI-type lenses including AI-modified Nikkor
lenses: Confirm aperture value on lens barrel,
With lenses having fixed aperture, such as Reflex-
Nikkor lenses: Aperture cannot be changed , Adjust
exposure by changing shutter speed ,
With lenses having no auto diaphragm such as pc-
Nikkor lenses: Lens is stopped down when a smaller
aperture (larger f-number) is selected , Focus manually
with the lens set at maximum aperture,
4. To take the picture, fully depress shutter release button,