Nikon D3X - Manual (Page 366)

340
U
f6: Assign AE-L/AF-L Button
Choose the role played by the AE-L/AF-L
button, either by itself ([AE-L/AF-L button
press]) or when used in combination with the
command dials ([AE-L/AF-L+command
dials]). The options available for [AE-L/AF-L
button press] are the same as for [FUNC.
button press] (pg. 333), except that [AE-L/AF-L button press]
defaults to [AE/AF lock] and has an additional
B option (if this
option is selected, pressing the AE-L/AF-L button has the same effect
as pressing the
B button to initiate autofocus). The options
available for [AE-L/AF-L+command dials] are the same as for
[FUNC. button+dials] (pg. 336), except that [AE-L/AF-L +command
dials] defaults to [None] and lacks [1 step spd/aperture] and [Focus
point-selection] options.