On Wednesday I had the pleasure of a one-on-one Sussex photography day with Justine who has been taking lovely photos for some time.  One of the first things we did was to set her camera to back button focusing and I thought my explanation of the advantages of this focus system could have been defined more succinctly. Better late than never (!) so here goes.

What is back button focusing ?

Almost all cameras come factory set with the focus activated when we hold the shutter button half way down and you then take the photo by pressing it further. This is probably how the majority of people expect a camera to work. There is however a much better way of dealing with focus by taking it off the shutter button and assigning it to the back focus button which is then operated by our thumb.  It seems illogical at first as we are so tuned to working the other way round but with this system there is no more pressing the shutter half way down to focus. The shutter button is now used purely for taking the actual photo.

Back button focusing advantages

Although it will feel odd at first, there are some major advantages of using back button focusing.

1. Your focus will hold even if you release the shutter button. Using the shutter button to focus means you have to always find that perfect pressure point half way down. It’s common to either accidentally release the button and lose focus or press it too hard and take a photo when you’re not ready.
2. It’s much easier to focus and then recompose. When your shutter button controls your focus, as soon as you recompose an image and press the shutter half way it will attempt to refocus – often on something unintended in your photo. When your subject sits in part of your frame not covered by one of your focus points you have to focus and then recompose your shot. After your first shot if you release the shutter button you have to do this all over again. With back button focusing all you have to do is focus one time, recompose and shoot away.
3. No more changing between single and continuous focusing.  The fewer buttons and changes you have to make on your camera the less shots you’ll miss and the better you can concentrate on your composition. I use Nikon cameras which are now always set to continuous focus as this setting when combined with back button focusing enables me to increase my chances of capturing moving objects whilst also being perfect for still subjects. 

Here’s a set of three photos taken last year on my Borneo orangutan tour using this technique. The camera has nailed the focus perfectly as the Proboscis monkey jumped into the river leading to the third image of a reflection when it hit the water.