Back button focus

Back button focus usually confuses photographers at first but once you get used to it, you will wonder why you did not learn to do it sooner. If there is anything I wish I had learned sooner in my photography, it would be this one simple thing: Back Button Focus. This has been quite possibly the biggest game changer in my photography.  I have noticed a remarkable difference in the accuracy of my focus.
 Within your camera’s menu settings, you have the ability to assign certain functions to different buttons on your camera. Most DSLR cameras, by default, set focus by pressing the shutter button halfway down. Back button focus simply changes the method of focusing by assigning the focus function to another button on the back of your camera (this button could be different depending on your camera model). This means that your index finger is now solely responsible for releasing the shutter, and your thumb is now responsible for focus.It takes practice to get used to this but like anything practice makes perfect.
While many would argue that this makes it more complicated, I would have to disagree, however it does take a bit of practice to assign the thumb to do another job without thinking about it, muscle memory not a conscious thought. While at first it may be different than you are used to, using your thumb and index finger simultaneously is certainly no more complex. Simultaneous use of fingers is something we do all the time in everyday life!
When you remove the focusing function from the shutter button, you enable yourself to focus the shot and then recompose the shot as needed, while your subject stays in focus, especially useful in weddings, portraiture, Sports and Wildlife. When the shutter button controls your focus, as soon as you recompose the shot and press the shutter, the camera will attempt to refocus again, leaving your intended subject out of focus. Sure, you could bypass this by locking focus, then switching your lens into manual focus, but what a hassle.
 Some would say that focusing and recomposing should be avoided, and that you should just toggle your focus points. That is fine unless like me you are a left eye shooter and you move the focus point with your nose so you have the focus locked at all times. I spot focus so my focus is locked at all times.When I shoot Macro, Astro or Landscapes and using a tripod I will often shoot manual focus, so no need for BBF.
Once again as I have said before it is your CHOICE, make sure you have all the information before you make the decision, I love it, but that is my CHOICE.