Nikon D90 - Manual (Page 194)

174
L
a2: Center Focus Point
This option (available in all shooting modes) determines the size of the center focus
point.
See page 54 for more information on focus settings.
a3: Built-in AF-assist Illuminator
Choose whether the built-in AF-assist illuminator lights to assist
the focus operation when lighting is poor. This option is
available in all shooting modes except
l and m.
A The AF-Assist Illuminator
The AF-assist illuminator has a range of about 0.5–3.0 m (1 ft. 8 in.–9 ft. 10 in.); when using the
illuminator, use a lens with a focal length of 24–200 mm and remove the lens hood.
A See Also
See page 231 for restrictions on the lenses that can be used with AF assist.
Option Viewfinder display Description
c
Normal zone
(default) Focus on stationary subjects that can be easily framed
in the focus point.
7 Wide zone
Focus on moving subjects. Not available when Auto-
area is selected for Custom Setting a1 (AF-area
mode).
Option Description
On
(default)
If the subject is poorly lit, the AF-assist illuminator will light to assist the focus
operation in single-servo AF (AF-S selected for autofocus mode, or single-servo AF
selected in AF-A autofocus mode) when Single point, Auto-area, or 3D-tracking
(11 points) is selected for Custom Setting a1 (AF-area mode) or when Custom
Setting a1 is set to Dynamic area and the center focus point is selected.
Off
The AF-assist illuminator does not light to assist the focus operation. The camera
may not be able to focus using autofocus when lighting is poor.