Nikon D300 User Manual page 72

a9: Built-in AF-assist Illuminator
Choose whether the built-in AF-assist
illuminator lights to assist the focus
operation when lighting is poor.
On
(default)
off
Description
The AF-assist illuminator lights when lighting is poor. AF-
assist illumination is only available when both of the
following conditions are met:
1. Single-servo autofocus is selected for focus mode (pg. 62).
2. Auto-area AF is chosen for AF-area mode (pg. 64), or
single-point or dynamic-area AF is chosen and the center
focus point is selected.
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.
[] 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.
[] See Also
See page 355 for restrictions on the lenses that can be used with AF assist.
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