A reader sent me an email asking about the back button focus on cameras. Specifically, the question below.
I don’t get the difference between doing that and simply shifting the focal point. Is there a difference?
Before talking more about the back button focus feature of cameras, I want to quickly answer the reader’s question.
Yes, there is a big difference between back button focus and shifting the focal point. First I will talk about shifting the focal point. When someone refers to focal point shifting he/she is typically referring to using a large aperture and then opening up to a small aperture. The effect of this is a change in depth of field and the amount of the foreground and background are in focus versus blurred. You can learn more about that at Photography Life.
Back Button Focus
Now on to one of my favorite camera features, back button focus. This is where you set a button on the back of your camera (typically near your thumb) to obtain focus. On many cameras, setting the button that way will disable the shutter’s half-press focus feature.
An advantage to using the back button for focus is that it will prevent your lens from re-focusing when unwanted. It will enable your camera’s lens to stay manually focused when the button is not pressed.
That way when photographing a landscape, a long exposure, sports or any subject matter really, you have better control over auto-focus.
It also helps for improved focus tracking when capturing motion. Combine the back button focus with a continuous style focusing mode and you will see much better results than if half-pressing the shutter.
Out of the box, every camera handles focus the exact same way. You press the shutter button halfway down to lock focus, and then you smash it the rest of the way to take the picture. One button, two entirely different jobs. It is intuitive, it makes sense to beginners, and it is how manufacturers setup gear by default.
Back-button focus completely kills that setup. It strips the focusing job away from your index finger and hands it to your right thumb on a rear button, usually labeled AF-ON. Your thumb handles the focus tracking, and your index finger handles the story capture. Two buttons, two separate jobs.
I remember when I first switched over to this system years ago. My muscle memory fought me hard for the first week, and I missed a handful of frames because I simply forgot to press the back button. It is a normal hurdle, and I guarantee you will feel that same frustration at first. Stick with it for a week or two. Once it clicks, you will never go back to the factory defaults.
Separating these controls gives you complete authority over your frame, speeds up your workflow, and saves you time in post-processing.
Why Separating These Controls Matters
The biggest benefit of back-button focus is that it eliminates the need to constantly flip your camera switches between Single AF (AF-S) and Continuous AF (AF-C). You can leave your camera permanently locked into continuous tracking mode.
- For moving subjects: You simply plant your thumb on the AF-ON button. The camera will continuously track the subject as long as your thumb holds the button down, letting your index finger fire shots at the exact right moment.
- For static subjects: You tap the AF-ON button once to lock focus on your subject, and then you let go. The camera is now essentially locked into place. You can fire twenty frames in a row, and the camera will not try to refocus or hunt when you press the shutter button.
- For shooting through obstructions: If you are tracking a subject and a person or an object moves across your frame, you just lift your thumb. The autofocus stops driving instantly, holding your focal plane right where your subject is. Once the obstruction passes, you mash your thumb back down to resume tracking.
This is a massive win for event photography and quiet observation. You stop accidentally refocusing between portrait frames, and you gain the ability to pre-focus on a specific spot, like a doorway or a stage mark, waiting for the action to happen without your lens hunting at the absolute worst moment.
The Mirrorless Reality Check
We need to be completely honest here. The argument for back-button focus was incredibly strong back in the old DSLR days when autofocus systems were limited to a tiny cluster of points in the center of your optical viewfinder.
Modern mirrorless systems have shifted this landscape significantly. The real-time eye and subject tracking on bodies like the Nikon Z8 or Sony a7 IV is incredibly intelligent. If you are shooting a portrait session with continuous eye-detection turned on, the camera tracks the eye across the entire frame automatically. The old “focus-and-recompose” method is mostly dead because the tech handles it for you.
Because of this, some photographers have moved back to shutter-button focusing on mirrorless bodies. That is totally fine. Gear and settings should always serve your specific workflow, not someone else’s rules.
I still stick with back-button focus because I want absolute tactile control over when my camera drives the lens and when it stays completely still. If I am shooting through branches, pre-focusing a scene, or building a multi-shot panorama, I want to decide when that focus shifts, not an algorithm.
How to Set It Up on Your Gear
The setup logic is identical across every single manufacturer: you must disable autofocus activation on the shutter button, and ensure a rear button is mapped to trigger the AF-ON command.
- Nikon (Z System): Head into your Custom Settings Menu (the pencil icon), look for section a: Focus, and select a6: AF activation. Switch this setting to AF-ON only. On a body like the Nikon Z8 or Z6 III, you have a dedicated rear AF-ON button ready to go. On the retro Nikon Zf, use the Custom Controls menu to map the AE-L/AF-L button to the AF-ON function.
- Sony: Navigate to the Focus tab, select AF/MF, and look for AF w/ Shutter. Turn this completely Off. Next, hop into the Setup tab under Operation Customize, and ensure your rear AF-ON button is mapped to the AF Oncommand.
- Canon (EOS R System): Open your menu and dive into Custom Controls. Look for the shutter button icon and change its half-press behavior from “Metering and AF start” to just Metering start. Then, ensure your rear AF-ON button (or the asterisk button on smaller bodies) is assigned to Metering and AF start.
- Fujifilm (X System): Open your menu to Setup, select Button/Dial Setting, and look for Shutter AF. Fujifilm splits this by mode, so you must turn this setting Off for both AF-S and AF-C individually. Then confirm your rear AF-ON button is active.
The Downside to Keep in Mind
There is one major practical headache with this system: it ruins your camera for anyone else.
If you hand your camera to your assistant, a second shooter, or your family member to take a quick photo of you, they will instinctively half-press the shutter, click the frame, and hand you back a completely blurry, out-of-focus image. They do not know your thumb is supposed to do the heavy lifting. If you share your gear frequently or pass your camera off to others, you will constantly have to explain the system or jump back into your menus to reset it.
Give it a shot for two full weeks. Force yourself through that initial awkward phase where your thumb and index finger fight for control. If it makes your shooting more intentional and speeds up your delivery times, keep it. If it slows you down, switch it right back. The goal is a clean, frictionless workflow that gets you out of the editing room and home to your family faster.
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