In the Miami office our customers very frequently want to set a camera so that a button on the rear (used with your thumb) will activate the Autofocus system but the shutter release does not. This is useful if you wish to shoot multiple frames after a focus-and-recompose.
More Information on why you would want to set the camera this way.
On just about every camera this requires changing a custom function or two. Soon owners of P40+ and P65+ digital backs will be able to set the custom functions of a DF body using the digital back’s LCD. Until then here is way to set this configuration using the DF Body.
Summary
Set CF#12 to Option 1
Set CF#9 to Option 1
Set CF#10 to Option 2
Step-by-step
1) Rotate your Mode dial to “CF” to access the custom function list.
2) Under CF#00 rotate the thumb dial to select Custom Function Set A. This allows you to make changes from the defaults which will be stored in Set A. This also allows you to set up three different custom function sets (e.g. for three styles of shooting or for three different photographers sharing a camera) and also allows you to always return to the default settings (by selecting — instead of A B or C) without having to “reset” the camera.
3) Rotate the front finger dial to function #12 and then the thumb dial to set custom function #12 to option 1. This sets the AF-L button to be an AF-On button so instead of locking focus it engages the AF engine.
4) Rotate the front finger dial to function #9 and then the thumb dial to set custom function #9 to option 1. This switches the AEL (normally on the rear) and AFL (normally on the front) so that now the rear button engages Autofocus.
5) Rotate the front finger dial to function #10 and then the thumb dial to set custom function #10 to option 2. This removes autofocus from the shutter release.