Back-Button AF

[bwana]

I spent today getting to grips with the idea but it's going to take a while longer to focus on my focusing.

First off: why would anyone want to remove AF from the shutter button?
This is a question many users ask when Back-button AF is first explained to them. There are certainly many times where the standard method of operation — press the shutter button half-way down to focus, and then press fully to shoot — works perfectly well. Everything is controlled by one finger, and if you like, you can lock the focus with a stationary subject by holding the shutter button half-way down. Even dedicated supporters of back-button AF will change back to standard camera operation from time to time.

Plenty of other tips and tricks available.