Back button focusing: what it is and how to use it | Articles | Photo, video, optics

Back-but­ton focus­ing, also known as AF-ON but­ton focus­ing, is one of the many handy lit­tle details that help pho­tog­ra­phers. We fig­ure out why you need back but­ton focus­ing and how to use it on Nikon, Canon and Sony.

What is back button focus

Back but­ton focus­ing is one way to focus. It is done using the “AF-ON” but­ton. This but­ton removes the task of focus­ing from the shut­ter but­ton. There is a but­ton on the back of the cam­era that is easy to reach with your thumb. That’s why it’s called the back focus but­ton.

What is back button focusing for?

The AF-ON but­ton allows you to lock the focus before shoot­ing — this way you can avoid focus­ing errors when chang­ing com­po­si­tion when we press the shut­ter but­ton. In addi­tion, this key allows con­tin­u­ous focus­ing regard­less of the focus mode set­ting.

As long as you keep the AF-ON but­ton pressed, the cam­era will con­tin­ue to focus. How­ev­er, when you release the AF-ON key, the cam­era will lock focus.

Benefits of back button focusing

Back but­ton focus allows you to switch between con­tin­u­ous and sin­gle focus with­out chang­ing set­tings (AF‑C for mov­ing sub­jects, or AF‑S for sta­tion­ary sub­jects). So, you have more time to react if the object sud­den­ly starts to move: for exam­ple, a child who was sit­ting in a sand­box sud­den­ly got up and ran.

Back but­ton focus­ing is also use­ful for macro pho­tog­ra­phy when the aut­o­fo­cus sys­tem is unable to focus on what you think is the main sub­ject. Because the cam­era locks focus when you press the AF-ON but­ton, you can focus on the sub­ject and then move the cam­era to improve the com­po­si­tion. This is use­ful when you have a sta­tion­ary sub­ject and want to cre­ate mul­ti­ple com­po­si­tions of the same scene.

You need to make sure you don’t change the dis­tance between the cam­era and the sub­ject, because that will mess up the focus set­ting. Use a tri­pod to fix the posi­tion of the cam­era and change only the shoot­ing angle.

How to set back button focus

The hard­est part when you start work­ing with the AF-ON but­ton is fig­ur­ing out how it is con­fig­ured.

Each cam­era man­u­fac­tur­er pro­vides a dif­fer­ent way to enable back but­ton focus­ing. For exam­ple, old­er cam­eras may not have an AF-ON but­ton, in which case you need to fig­ure out which but­ton can be used instead and how to set it as the AF-ON but­ton.

Back button focus on Nikon

The lat­est Nikon cam­eras have an “AF-ON” but­ton and use the same path to set focus with this key.

The sequence is like this:

1. Open Menu (“Menu”);

2. Go to the Cus­tom Set­ting Menu (pen­cil icon);

3. Go to the Aut­o­fo­cus sub­menu;

4. Select AF acti­va­tion;

5. Select AF-ON only.

If you have an old­er Nikon cam­era, you may not have an “AF-ON” but­ton, but an “AE‑L/AF‑L” key instead. The menu may also look dif­fer­ent.

For exam­ple, for some Nikon cam­eras you need to run the fol­low­ing actionsto enable focus using the back but­ton:

1. Open Menu (“Menu”);

2. Go to the Cus­tom Set­ting Menu (pen­cil icon);

3. Next, go to the Con­trols sub­menu;

4. Select the Assign AE‑L/AF-ON but­ton;

5. Select AF-ON.

Even old­er mod­els (eg Nikon D3100) also have a dif­fer­ent menu. Be patient and nav­i­gate through your cam­er­a’s menus until you find the AF-ON but­ton options.

Back button focus on Canon

Again, there are dif­fer­ences between mod­els, but the main thing you need to do is dis­able aut­o­fo­cus on the shut­ter-release but­ton and enable focus with the AF-ON but­ton.

To dis­able aut­o­fo­cus on the shut­ter-release but­ton:

1. Open Quick Menu or Menu and nav­i­gate to Cus­tom Con­trols;

2. Select the half-press shut­ter icon — it looks like a shut­ter release and is locat­ed in the top left col­umn. Then click Set to open the sub­menu;

3. Select the Meter­ing start option and press Set to con­firm your selec­tion.

To enable the AF-ON but­ton for focus­ing:

1. Open the Quick Menu or (Menu) and go to the Cus­tom Set­ting Menu;

2. Select AF:On from the sub­menu;

3. Select the Meter­ing option and AF start; (Start Aut­o­fo­cus) and press Set to con­firm your selec­tion.

Back button focus on Sony mirrorless cameras

Sony cam­eras don’t make things easy either. As with Canon cam­eras, you need to do two things: first remove the focus func­tion from the shut­ter but­ton, and then acti­vate the “AF-ON” but­ton. For this do the fol­low­ing:

1. Open Menu (“Menu”);

2. In tab 1, go to page 6, select AF w/shutter and turn it off;

3. Return to the main menu, go to page 7, select Pre-AF and turn it off;

4 Return to the main menu, tab 2, go to page 8 and select Cus­tom Key;

5. Switch to tab 3 and select the AE‑L but­ton;

6. Select AF On and press OK;

7. Select the AF but­ton and press OK.

Outcome

All the but­tons and set­tings on your cam­era have a spe­cif­ic pur­pose and can help you in the shoot­ing process. Under­stand the device of your cam­era, and it will serve you well.