how to back button focus

Back Button Focus

Have you ever heard of using the back button to focus on your DSLR?  It seemed very odd and foreign to me when I first heard of this.  With my finger already depressing the shutter ½ way down to focus it was easy to actuate the shutter.  The thought of adding an extra step in how I shoot make very little sense to me.  Still, I kept hearing about this back button focus thing.  So I decided to give it a try.  Here is what I discovered