A feature on your DSLR that can help you achieve sharper images in certain situations is back button focus. In this post, I will tell you what it is, how to find it on your camera, and situations where you may find it helpful.
WHAT IS BACK BUTTON FOCUS (BBF)?
In its most basic terms, back button focus is a feature which removes Autofocus from the shutter button and assigns it to a button on the back of your camera. You shutter button will still activate the shutter, but your lens's Autofocus is now activated by a button on the back of your camera, independent of the shutter.
Since this feature uses a button on the back of your camera (hence the name, back button!) to lock in the focus of your shot, you will not need to press the shutter button halfway before shooting in order to refocus every time you make an exposure. This helps ensure that a) once you have achieved sharp focus, you will not lose it on your next shot and b) you will spend less time focusing and more time actually shooting.
Current DSLRs being manufactured by Nikon and Canon's EOS line have this feature. BBF is also available on certain Sony and Pentax cameras, but you will need to check your camera's manual to verify that your camera has the feature. If you do not have your camera's user manual, I have included links at the bottom of this post on where you can find them.
In this tutorial, we will be looking at how to activate BBF on the Nikon D7000, Canon 5D Mark ii, and the Sony mirrorless A6000.
Note: back button focus should not be confused with "back focusing" - they are not the same thing! Back focusing is an issue that arises when there is trouble with focusing.
WHEN TO USE BACK BUTTON FOCUSING
As it is with just about any photography technique, there are certain times when back button focus will be perfect for you, and there are certain times where it will not work well at all. Here are some examples of when you could benefit from BBF:
Scenario 1 - Portraits and Stationary Subjects
BBF is great for portraits, as it gives you the ability to move your camera to recompose your shot without having to refocus. The key is to remain the same distance from you subject, or else you will need to refocus. If you remain at relatively the same distance, though, you can move your camera up/down and left/right without the need to refocus.
Scenario 2 - Moving Subjects
While BBF may seem like it is best-suited for stationary subjects, it can be very useful for moving subjects, as well, given that they remain at the same distance from your lens from shot to shot.
For example, let's say you are photographing a wedding, and, during the ceremony, the couple are at the altar for an extended period of time. By selecting the focus only once, and having the ability to continuously press the shutter without the camera refocusing for every shot, you will be able to more easily capture facial expressions and gestures which happen within a fraction of a second. If you are continuously refocusing during the ceremony, you run the risk of missing some really great, split-second, impossible to replicate moments.
ACTIVATING BACK BUTTON FOCUS ON YOUR CAMERA
The way in which you activate BBF will vary from camera to camera. Even though BBF is a simple concept, camera manufacturers do make setting up BBF a bit complicated sometimes!
The common denominator, though, is that you will first need to know which button on the back of your camera will lock in the focus for you, and from there, you will use your camera's menu to find your back button settings, and assign the focus to the button on the back of your camera, so that instead of your shutter button being the command for your lens to focus, your back button will now focus for you (but your shutter button will still activate the shutter).
On Nikons, BBF is assigned to the AE-L/AF-L button:
For Canon cameras, the AF-ON button is assigned BBF:
This is the button on Sony's A6000:
REFER TO YOUR CAMERA MANUAL TO LOCATE BACK BUTTON FEATURES
If you do not have your camera's manual, you can download a copy through the manufacturer's website. Here is a list of popular manufacturers, with links to their camera manual libraries:
Did you find this information helpful, or do you have any questions about BBF? We love hearing from you! Please visit us in our private Pretty Photoshop actions Facebook group!
Here are quick links to the other blog posts in our Guide to Shaper Images Series: