84 — Back (rear) button autofocusing

Pho­tog­ra­phy pod­cast #84 is based on a sin­gle com­ment by Richard from our forum where he men­tions rear-button aut­o­fo­cus to aid in sharp­ness. This tech­nique was devel­oped by Canon about 20 years ago but I first heard of this tech­nique on the MPB pod­cast (link in shownotes — thx for find­ing it for me Mar­tin!) about two and a half years ago. Basi­cally this tech­nique REMOVES aut­o­fo­cus­ing from the shut­ter release but­ton and assigns it to a but­ton on the back of the cam­era. Espe­cially when track­ing a mov­ing sub­ject, this is a great tech­nique and will likely get you more keep­ers. It will also STOP your aut­o­fo­cus from track­ing things that you don’t want it to.

Finger positions for rear button autofocus

Fin­ger posi­tions for rear but­ton autofocus


Ducks — Even though ducks are entering/exiting the scene, aut­o­fo­cus is not lost on the cen­tral duck which I was track­ing. The aut­o­fo­cus­ing can­not ‘hunt’ for any other duck because I am track­ing and lock­ing focus on only 1 duck.

Links /resources men­tioned in this podcast:

Excel­lent Rear but­ton aut­o­fo­cus arti­cle by Canon
Rear but­ton aut­o­fo­cus dis­cussed on the Mar­tin Bai­ley Pod­cast
July 2010’s — Per­spec­tive and/or Lead­ing lines assign­ment
Publicphotograpgy.orgCel­e­brat­ing the rights of pho­tog­ra­phers -Publicphotography.org — Flickr groupPublicphotography.org — Face­book group

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Thanks to Jackie Sheen, Jason and Glenn Euloth who posted a blog com­ment about our last pod­cast. Thanks as always to every­one that sent com­ments by email about our last pod­cast. Although ALL com­ments are appre­ci­ated, com­ment­ing directly in this blog is pre­ferred. Thanks as well to all the new mem­bers of the bul­letin board.

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  1. Aseguin says:

    Nice tip. I heard this men­tioned before, but I thought it was only for higher end cam­eras that had a back af but­ton. I just changed it on my cam­era and really enjoy it. Much eas­ier. I use to hate it when I would hold my shut­ter release half way and by mis­take I would press to hard and release the shutter.


  2. Richard says:

    Thanks for another great podcast,

    I leave my cam­era with BB focus on all the time now as it suits my shoot­ing style. It does con­fuse the hell out of any unsus­pect­ing per­son who picks up my cam­era with out ask­ing me first and then won­ders why all their shots are out of focus.

    One easy way around this on my 450D is…

    if you put the cam­era into an Auto mode it tem­porar­ily dis­ables the rear but­ton focus, and then re-enables it when you switch back to man­ual, or Av Tv mode etc.

  3. admin says:

    Thanks for the com­ments guys! Excel­lent extra info there F8!

  4. f8&Bthere says:

    Another very good dis­cus­sion in a pod­cast is by the Nikon­ian Image Doc­tors:
    I don’t shoot so much sports and wildlife, but I’ve been using the tech­nique exclu­sively for almost a few years now and the big thing for me is how easy it makes focus and re-compose. I usu­ally like to shoot with the AF set to cen­ter point. But hav­ing the AF “tied” to the shut­ter but­ton just makes me uncom­fort­able– I guess it’s my own lack of dex­ter­ity, I just think get­ting that half-press and hold thing right doesn’t work for me. I’m always trip­ping the shut­ter or releas­ing pres­sure caus­ing the AF to refo­cus when I don’t want it to. The AF-on tech­nique solves all that for me, and I could never go back now. For exam­ple, when por­trait shoot­ing I can put the AF point right over my subject’s eye, hit the AF-on but­ton, then re-compose as desired not wor­ry­ing about the shut­ter but­ton mess­ing up my focus. So it’s not only great for mov­ing sub­jects in dynamic AF mode.
    One last impor­tant point for Nikon shoot­ers using VR lenses (not sure if it applies to Canon IS or oth­ers). On cur­rent Nikon bod­ies, the AF-on but­ton will not engage VR. Only the shut­ter but­ton can do that. And since it takes a brief moment for the VR sys­tem to engage, the time that a nor­mal AF shooter would half-press the shut­ter to grab focus, a AF-on shooter using VR may have to just give a quick light press to the shut­ter but­ton prior to snapping.

  5. RobvE says:

    Heard about this tech­nique a while back, tried it, and now use it all the time. Ideal combo between sin­gle shot focus and con­tin­ues track­ing.
    Only change when I want some­body else to take pic with my cam­era. Have the set­ting in the quickmenu.

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