Nikon D300 Complete Manual page 588

Aperture setting
Sub-command dial The appropriate Command dial
Aperture ring
Menus and playback
Off
On
136 The Front Command dial doesn't always control the aperture as implied by Nikon's
default choice; after all, you can change that function with another option in this
same Custom Setting!
137
On AI and other lenses without CPUs, this is effectively the default for this setting.
Thom Hogan's Complete Guide to the Nikon D300
the Front Command dial controlling shutter
speeds, for instance.
controls the apertures
The aperture ring on the lens is used to
control the apertures
The Direction pad is used to control
navigation in menus and playback [default]
The Command dials are used to control
navigation in menus and playback in addition
to the Direction pad (the Rear Command dial
is equivalent to the left/right keys on the
136
[default]
137
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