The roles played by each of the function buttons can be selected by pressing and holding the button. The default options are shown below:
[Fn1] button (Photometry)
[Fn2] button (Control ring options)
[Fn3] button (Film simulation)
[Fn4] button (White balance)
[Fn5] button (AF mode)
[AEL/AFL] button (Exposure/Focus lock)
Center of rear command dial (Focus check)