Nikon D300 - Manual (Page 297)

271
U
a5: AF Activation
This option controls whether both the shutter-release button and
the
B button can be used to initiate autofocus, or whether
autofocus is only initiated when the B button is pressed.
a6: AF Point Illumination
Choose whether the active focus point is highlighted in red in the
viewfinder.
Option Description
Shutter/
AF-ON
(default)
Autofocus can be performed with the B button or by
pressing the shutter-release button halfway.
B only Autofocus can only be performed using the B button.
Option Description
Auto
(default)
The selected focus point is automatically highlighted as
needed to establish contrast with the background.
On
The selected focus point is always highlighted, regardless of
the brightness of the background. Depending on the
brightness of the background, the selected focus point may
be difficult to see.
Off The selected focus point is not highlighted.