Nikon D5100 Reference Manual page 12

Choose the role played by the AE-L/AF-L b utton.
_-_!_ -O_ption -_- .... Description ....................................... ............
I_] AE/AF Focus and exposure lock while the AE-L/AF-L button is
lock )ressed.
!_1 AElock Exposure locks while the AE-L/AF-L button is pressed.
only
t_i AFlock Focus locks while the AE-L/AF-L button is pressed.
only
Exposure locks when the AE-L/AF-L button is pressed, and
_.. AElock remains locked until the button is pressed a second time
-"_),Hold,_ _ or the exposure meters turn off.
The AE-L/AF-Lbutton initiates autofocus. The shutter-
AF-ON
release button can not be used to focus.
Select Yes to reverse the rotation of the command dial.
AE-L/AF-L button
Selecting Enable release allows the shutter to be released when no memory card is
inserted, although no pictures will be recorded (they will however be displayed in the
monitor in demo mode). If Release locked is selected, the shutter-release button is
only enabled when a memory card is inserted in the camera.
At the default setting of ._... • o .... (+o-), the exposure indicators in the
II _!t II II II II II II | 111111 tl II II I_
viewfinder and information display are displayed with positive values on the left and
negative values on the right. Select .... o,., ._ (-o+) to display negative
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values on the left and positive values on the right.
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