Back Button focus on D3100 question?
#1. "RE: Back Button focus on D3100 question?" | In response to Reply # 0MEMcD Nikonian since 24th Dec 2007Thu 27-Oct-11 01:15 AM
Change the fuction of the AE-L/AF-L Button to AF-ON.
That will decouple the AF fuction from the shutter button and transfer it to the AE-L/AF-L button.
See Page 146 of the D3100 Users Manual.
It will work the same way on the D3100 as it does on the D300.
Good Luck and Enjoy your Nikons!