Nikon S6400 manual AF Assist, E99

AF Assist

Tap F Mz(setup menu) MAF assist

Enable or disable AF-assist illuminator, which assists autofocus operation when the subject is dimly lit.

Option	Description
	AF-assist illuminator will be used to assist the focus operation when
	the subject is dimly lit. The illuminator has a range of about 1.9 m (6 ft
sAuto	3 in.) at the maximum wide-angle position and about 1.5 m (4 ft
	11 in.) at the maximum telephoto position.
(default setting)
	Note that for some scene modes (such as Museum (A46) and Pet
	portrait (A49)) or focus areas, the AF-assist illuminator may not
	light even when Auto is selected.
pOff	AF-assist illuminator does not light. The camera may be unable to
	focus under dim lighting.

Reference Section

E99