Setting up Rear-Button Focus

A lot of people ask me about back-button Auto-focus.  I figure it is time to write about this.

Generally we autofocus from half-pressing the shutter button.  When we finish pressing the shutter button, an image is made.  This is great and how just about all cameras work.  There comes a point where you might find yourself in a situation where you want to autofocus, but you want to make multiple images without the focus resetting or changing every time you press the shutter.  For instance a studio set up or a landscape scene.  Another instance would be a scene where your subject is not changing distance but you want to capture multiple shots or expressions and not refocus.  Sure you could put the camera in manual focus…but if you prefer autofocus, or need to autofcous but just not on every shot…why not have an option?  As it turns out most cameras do.

We can remove the focusing from the shutter button and move it to another button.  On most cameras this means a button on the rear of the camera near the thumb position.  This allows you to focus with your thumb and fire the camera with your finger on the shutter.  Once you have tried this, it might become your favorite way to work.  A lot of people shoot like this.  I personally go back and fourth depending on my subject matter.

Let me elaborate a little bit on how I personally use this feature, and then we’ll explore how to set up your camera.

I generally move the focus to Function Button 1 on the rear.  This lets me focus with my thumb.  I normally set the camera to S-AF+MF.  This lets me autofocus with the rear button, but then also manual focus at will from the lens if I need to refine or adjust.  It allows me to manual focus and then shoot freely, but if something comes up and I need to autofocus quickly, I still have my rear button ready with my thumb over it.

I have a secondary function set up as well.  Olympus cameras are the only ones i’ve worked with that let us customize ANY button to be a focus button.  Thank you Olympus!  I do a lot of ground level shooting.  I like low perspectives, and often when shooting landscape or nature macros I have the camera virtually on the ground.  This makes holding the camera traditionally very hard.  The focus button is easy to trigger from on top, but the rear focus button becomes more difficult.  So I have also programmed one of the top custom buttons (the record button) to be a secondary focus button!  All I have to do is press the record button and my camera focuses!  This makes waist-level and ground level shooting a breeze.

I will say personally, the shutter button feels a lot more responsive and quicker to action than any other button on the camera.  If you need sharp decisive focus without any delay, the shutter button still feels best for this.  The rear buttons have a different “press” feel.  It’s slightly more effort to press, and they aren’t as large.  Small trade-off.  Often when I use continuous autofocus I will switch back to shutter button focus.  Again, it comes down to personal preference.  I would try both and see which works best for you.

So how do we set this?  We do it in 2 steps.

1. Menu Button > Custom Menu A1 > AEL/AFL > S-AF > Mode 3

This establishes that you want to move focus duties away from the shutter button and move it to the AEL/AFL command. The next step is to assign AEL/AFL  (Auto-exposure lock / auto-focus lock) to whatever button you choose.  This would make that button your focus button.  You do that with this next step.

2. Menu Button > Custom Menu B > Button Functions > Select a button and set it to AEL/AFL option.

Any button in the menu can be customized to the AEL/AFL option.  Again, I set Function Button 1 to AEL/AFL and I ALSO so Rec Button to AEL/AFL.  I have two focus buttons in this way.  You can set focus to whatever button you like.  You could even set your lens button to be your focus button!  Fancy that!

Some times handing a camera to someone else…they don’t “understand” rear button focus at first.  So if they are taking a picture of me or a family group shot, they end up being out of focus since they think the shutter is focusing.  Even when I tell them.  I have a custom mode saved that has focus on the shutter and face detection on just for handing the camera to others!  All my main working modes have Fn1 as Focus, and Rec as focus.  My lever changes from S-AF+M  to Continuous focus but on the shutter.  Kind of complex but it works great.  You can actually set continuous focus separately from single autofocus.  That is set up by repeating step 1 above and selecting continuous AF assignment.

What is your preference?  Do you find one faster than the other?  Are there any other buttons you use as focus, and if so what benefit do you get or what specific scenarios call for this?


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3 thoughts on “Setting up Rear-Button Focus

  1. Dear Tony

    Thanks for sharing your thoughts on setting AF with the ‘Back Focus Button’. I only started using this technique over the past few weeks and there’s one thing which I’m unclear about.

    (1) After setting focus using the ‘Back Button’ > I release the button > take my time to wait for the right moment, the right smile, or the right expression, etc.

    (2) When I’m ready > I press the ‘Shutter’ release button and the ‘IBIS kicks-in’ > the image in the EVF normally ‘jump or jerk’ a little due to the image stabilization.

    *My Concern Is*
    Will the ‘kicking-in of the IBIS’ (after the shutter release button is pressed) ‘affect or alter’ the focus which I had earlier set with the ‘Back Button’?

    I hope to hear your feedback on this concern so that I can use this technique with confidence – which I really like and enjoy using :-)

    Yours sincerely,

    1. Yes this little nudge from the sensor shaking is interesting…i’ve even had it adjust my composition a little when on a tripod. In terms of AF and dealing with this I would ONLY be concerned in very extreme macro scenarios. Situations where you are very close and working with a very shallow depth of field. Otherwise the sensor is just not shifting enough to move you out of the plane of focus, or introduce a scheimpflug effect. (tilt/shift) Or at least that is from my experience. If it could, that would be amazing to be able to utilize! Then again, the Pentax cameras can move far enough to handle astro photography for up to 5 minutes apparently. It is the Astrotracer feature. I have not used it…and I wonder what focal length is the max usable. Regardless…quite the tangent. If you are not up macro close, you have nothing to worry about in terms of focus shifting from IBIS.

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