Today I would like to introduce you to a change you should make in your focus controls. This is a change you probably don’t think you need. Even after I tell you about it, you might not think it terribly useful. But it is. People I have taught have consistently pointed to this change as one of the more significant things they learned in my classes.
It is called back button focus. First I will tell you what it is and why it will help you. After that I will show you how to set it on your camera.
What Is Back Button Focus?
Normally, your camera sets the focus point when you press the shutter button half-way down. With back button focus, however, what you do is set the camera so that it changes that. Instead of using the shutter button to set the focus, the camera will set the focus when you press a button on the back of the camera. All you are doing is changing the button that sets the focus.
The Benefits of Back Button Focus
Why would you do this? Doesn’t using the shutter button to set the focus point work just fine?
Well, yes, it does. But back button focus is better in some circumstances. In particular, it works better where you don’t want the camera to reset the focus before the shot. With normal focus (using the shutter button), you can scarcely take a picture without the camera resetting the focus point. After all, you need to use the shutter button to take the picture, and that is the very button that sets the focus as well.
When you use back button focus, however, the two operations (focusing and taking the picture) are separated. Now you can set your focus once and take as many pictures as you want using the same plane of focus. There is no chance of the camera resetting the focus point.
When might you use this? There are a variety of circumstances, but for us outdoor photographers, a common scenario is when you are set up on a tripod and taking multiple shots. You might be waiting for some something to happen or just taking different pictures as the light changes. You doubtlessly set your focus point before the first shot, and you don’t want the camera trying to reset it every time you take a picture. With back button focus, you can be assured of this. The camera will not try to reset your focus point no matter how many shots you take.
Using Back Button Focus with the “Focus Then Recompose” Method
If you are familiar with the “focus then recompose” method of setting your focus, back button focus may appeal to you right away. What you do when you focus then recompose is (just like it sounds) set your focus point without regard to the final composition, then move your camera into final position to take the picture. Using the normal way of setting the focus with the shutter button, you would have to hold the shutter button down halfway as you set up the final shot. If you remove your finger from the shutter button, the camera will likely attempt to re-focus when you take the shot. With back button focus, on the other hand, you simply press the back button to set the focus, and that is the focus point that will be used for the final shot. It is much easier and less likely to lead to focus problems.
How to Set Back Button Focus
If you want to set your camera to use the back button to set the focus, how do you do that?
Obviously it varies a bit by model, but typically what you will do is go into your camera’s menu and find where it allows you to reset certain camera controls. In Canon cameras, that is the “Custom Controls” menu item. Click on that and the following screen will appear:
From there, you reset the AF-ON button so that it starts the auto focus (noted as AF start). You should also change the shutter button control so that a half-press will no longer start the auto focus. That is the icon directly above the AF-ON button in the screen above.
As I am writing this, I only have my Canon camera with me, so I cannot give you the specifics for other models. I will try to update this later. It should be a similar procedure though.
Using Back Button Focus
You might be concerned that back button focus is difficult to get used to. It isn’t. The button is conveniently placed right where the thumb of your shooting hand goes. Very quickly the feeling will become natural.
You need not worry that you will forget to set the focus either. It has been ingrained in all of us since we first picked up cameras not to take the photo until we hear that satisfying little beep that tells us the focus is set.
As a result, I definitely think you ought to give back button focus a try. It is a minor improvement that can occasionally have significant results. It separates two camera functions that occasionally don’t work well together. Plus, it isn’t permanent, so if you find your don’t like it, you can always change back to the old way.