How To Use “Back Button” Focusing
by William Lulow
Note: This article was published six months ago, but I thought it important enough to republish it here. This is a technique that can speed up focusing as well as composition.
Here’s a neat little trick I read about in PDN last year. It’s called “Back Button Focusing.” I learned that you can assign a button on the back of your DSLR to use for your auto focusing tasks. Most DSLRS these days have a feature which enables the user to hold the shutter release button down half way to allow the camera’s auto focus mechanism to acquire proper focus on the subject. Then, when you actually release the shutter button all the way, the picture is taken. Re-assigning the AF task is a simple matter, but you need to consult your camera manual for how this is done with your particular camera.
With “Back Button Focusing”, you can use one of the buttons on the back of the camera to do the same thing. I have been using this technique all the time now and did so last year while photographing singer/songwriter Kathy Mattea in concert. I re-assigned the auto focus task to my AF button which I held down with my thumb while I pressed the shutter button with my forefinger, as always. I set up only ONE AF point in the center and while holding down the AF button on the part of the image I wanted to be sharp, I re-composed the shot and then released the shutter with my forefinger. What I found was that the whole procedure of using auto-focus seemed to go a bit faster because you are holding focus on the element you want to be sharp while composing your shot. I found it was much harder to do the same thing by holding the shutter release button halfway. I found it much easier to use both buttons. My images were sharper and my compositions better.
For these images, I aimed the center AF point directly on the singer’s face to make sure that it was sharp, held the “Back Button” down and released the shutter, keeping the AF where I wanted it:
Since most of my early concert shots were done in Black&White, I always like to shoot some frames in original monochrome mode when I’m shooting concerts these days.
So, try this technique out. See if you like it and it helps you with your AF tasks. I found it to be particularly helpful with subjects that move a lot. I’ve taken to using it with my normal studio portrait shoots as well. Just seems to make things faster and easier.