Using Back Button Focus and AI Servo Together



Back Button Focus and AI Servo:

Using these two things together is the way I am able to shoot fast action photos without using burst or sport modes.

Goals from this lesson:

  • Set up Back Button Focus
  • Set up AI Servo Mode
  • Start shooting using those two together.

{Important:  back button focus and AI servo do not usually work in any of the easy modes on your camera.  This includes sport, portrait, etc.  For this class make sure you are shooting in one of the manual modes (Program, aperture priority, shutter speed priority, or full manual) .  If you need a refresher, I highly recommend Photo Concentrate’s Essential Camera Skills e book.}

Back Button Focus:

By separating auto focus from the actual shutter button, I am able to focus on the subject as it is moving and take the photo when I want.   This allows me to frame the shot and pick the moment when I feel the shot is ready. I am able to engage the shutter without fearing that my camera will refocus, and that I’ll lose a shot because the auto focus is no longer on my subject.   If I hold the back button down (while in AI Servo, NOT One Shot – see below), the camera and lens will continually focus on the subject as it moves, so I can stay in one place and capture the action around me.

(BTW – This is also helpful when I have a stationary subject that I want to shoot in a few different compositions. I can focus on the subject with the back button, recompose the shot with the in focus subject wherever I’d like in the frame, and then take the photo without the camera losing focus on the subject.)


If your camera manual does not give you a good idea on how to set this up – this tutorial is great:  How to set up back button focus.  There are so many different types of cameras that it would be hard to address them all here.  Shoot me an email if you have troubles – we can figure it out!

AI Servo:

AI Servo (AKA as AF-C on Nikons) is the best auto focus mode for fast moving subjects.  AI Servo continues to focus on the subject as long as you hold the back button down. This is perfect for when animals (or humans, or machinery, etc) are moving around you.  You can continually frame the shot as you move your camera, holding the back button down, and clicking the shutter when you have an image you like in the frame.  This allows you to shoot without burst or sport mode because the camera is focusing on the action as it happens, and you can just click away as the subject goes by without waiting for the camera to re-focus.

Putting the two together:

Now that you have separated the auto focus function from the shutter button, you don’t have to worry about missing a shot because the camera refocuses as you press the shutter down to take the photo.  Practice by choosing a moving subject.  Stand in one spot as it goes by, and hold the back button down to see how the camera continually focuses as the subject moves.  Choose another moving subject, and click the shutter button and feel how the camera does not focus at all.  Now start doing the two together with another moving subject..

It will take awhile to get used to, but the more you do it, the better at it you get.  As you can see in the top video, I do the actions while I’m talking about it without even thinking about it.  Yay muscle memory!

Your Assignment:

Keep shooting – over and over and over again.  It doesn’t matter what kind of shots you take, or what the subject is, just get used to the feeling of using your thumb to hold down the back button, and your finger to click the shutter.

Be on lookout for the next lesson in a week that puts together back button focus, AI Servo, and shooting in aperture priority with exposure compensation.


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