Nikon D3100 AE-L AF-L Button - Great information on this for entry-level and top of the line Nikon DSLR cam… | Dslr photography tips, Camera nikon, Dslr photography
autofocus - How do i return my nikon d3100 back to auto focussing with the shutter? - Photography Stack Exchange
Back Button Focusing - Easier than you think! - Improve Photography