DSLR Photo Tip: What The Heck Is Back Button Focus?

Photography Tips

Today’s DSLR photo tip continues with our series of tips covering functions on your camera that you’re most likely not using. Let’s talk about back button focusing.

Normally, to focus on a subject, we pick the focal point we want, then depress the shutter button halfway. This sets the auto focus (and the exposure, if you aren’t using manual mode). Then we recompose the shot so that the focal point is where we want it in the frame and depress the button the rest of the way to fire the shutter. Most of the time, this is OK. But in certain instances, it can be a real pain in the patootie!

Photo captured by Gonzalo Facello; ISO 640, f/6.7, 1/180s.

Have you ever tried to photograph a scene in low light conditions? Often the lens can’t find the focal point and will keep moving back and forth trying to find something to focus on. By the time it actually does focus on something, the shot has long since passed. Not to mention that the final focus isn’t always where you want it to be.

Speaking of the final focus point not being where you want it to be…

I’m specifically thinking of a shoot where I was trying to get a portrait of a young girl with a bunch of tree branches and leaves framing her face and body. My lens kept focusing on the branches, and I had a heck of a time getting the girl in focus for each shot.

Photo by Elisa Paolini; ISO 200, f/5.6, 1/100-second exposure.

Or, what if for some reason you want your photo to be out of focus? This is common in stock photos. The photo subject is out of focus and they later add in a sharp focus product image and sales copy.

Or what if you’ve got a moving target like a kid on a swing? You will want to focus on one spot and shoot every time the kid hits that location. If your lens refocuses every time, you are most likely going to miss the shot.

In the same vein, what if you are at a race of some sort. You’ve picked an ideal spot. The background is perfect, and as the bicyclers or cars or runners round a corner, the action is at its peak! To get the shot, you will want to focus on one spot and shoot as your subject gets there—and not have to refocus every time.

One way to handle the problem is to use manual focus. This requires that you turn the focus ring on the lens to manually set the focus. There is a danger here in that you may inadvertently change the exposure. (Don’t discount this, I’ve done it!)

But the biggest reason to avoid manual focus is that many of us don’t have the best eyes, and autofocus is just plain better. This is one of the few times I recommend an auto setting over manual.

A better way (than manual focus) is to use back button focusing.

What this does is remove the focusing function from the shutter button and move it to another button. Most DSLR cameras have added a button on the back of the camera for this function. (That’s why it is called back button focusing.)

In other words, once you set up your camera for back button focusing, when you depress the shutter half way, it doesn’t affect the focus. You can focus with the back button and the focus point will stay the same no matter how many shots you take and even if you change the exposure settings.

Photo by Tjarko Busink

Now, in that low light situation, you set the focus once and you don’t have to keep re-finding it. You can set your focus to have blurry shots if you want them, and pre-focusing on a certain spot is no problem.

3 Negative Aspects of Back Button Focusing

1. If you’ve never used it before, it takes a bit of getting used to. But one or two sessions and it will be as second nature.
2. If you let someone else use your camera, count on the fact that your shots will all be out of focus. They won’t know what to do.
3. You will have to actually get out your camera’s manual to figure out how to set it to back button focus.

It seems that the menu settings are slightly different for all the various models of camera, so it would be a waste to try and describe the settings here. Sorry, but you are going to have to bite the bullet and actually read your manual.

Once you’re comfortable with back button focusing, you will most likely leave your camera on those settings, but it can easily be changed back and forth to fit the situation.

Practice changing the settings back and forth so you are comfortable with them and can select the way you want to focus on any particular session.

About the Author:
Dan Eitreim writes for OnTargetPhotoTraining. He has been a professional photographer in Southern California for over 20 years. His philosophy is that learning photography is easy if you know a few tried and true strategies.