What is the practical use of the 'autofocus' back button?


weeloong

New Member
Jan 4, 2011
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#1
Hi all,

just wondering if anyone can share their experience on how this button helps in their shooting?

Thanks
 

Rashkae

Senior Member
Nov 28, 2005
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#2
Hi all,

just wondering if anyone can share their experience on how this button helps in their shooting?

Thanks
... by allowing you to disengage AF to maintain focus, or to lock AF, or to reset the selected AF point to the center one...

Without a clue as to what camera system you're talking about it's hard to make head or tails of what you are saying.
 

edutilos-

Senior Member
Dec 28, 2010
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#3
Hi all,

just wondering if anyone can share their experience on how this button helps in their shooting?

Thanks
I don't use it at all, but that's because of my preferred style of shooting.

This article brings up a lot of relevant points, particularly if you use a 7D.

How and Why I Use the Back-Button AF | Learning DSLR

Here's another one:

Andrew Yip Nature Photography » Why you should use the AF-ON button
 

Rashkae

Senior Member
Nov 28, 2005
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#6
help u to af when u are on live view mode
Ows? My camera doesn't need that button to AF in LV mode.

The specific function of that button will vary from manufacturer to manufacturer, then also in what mode you are in and if you set anything custom in the menu.

If you can't figure out a use for it, maybe you don't need the manual controls a DSLR can give.
 

David Kwok

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Aug 23, 2008
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#7
This question has been discussed awhile ago. I uses it on my Nikon system all the time, except when I need to pass the camera to a stranger whom has no idea how it operates. You set it to perform AF and your shutter release to only release without AF. In this way, this will allow you to release the shutter without refocus all the time.

The following as some advantages through my personal usage that I feel is useful.
1) Allows recompose even in continuous shooting mode
2) Useful in fast motion scenes such as sports, racing and fast moving subjects where you can you release the shutter without refocusing. Eg: In the event for soccer game when you can see a player is going to cut your line of sight when you are continuously focusing on another player further away, you can quickly release the AF button and the AF stops, the focus is likely still on the player when the intercepting player moves away. You can then capture immediately, or press the AF button again with less chances of focus hunting.

There are some quirks of course, because the shutter release no longer requires in focus to release, there are higher changes of out-of-focus should your subject is not in focus when you release the shutter. You will need to depend on your hunch, or visually on the in-focus indicator found in the viewfinder to indicate that you are in focus before release the shutter. This is not so much a problem for a slow photography event such as landscape or event, but for fast motion event, there is higher tendency for OOF.
 

farbird

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Jan 14, 2004
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#8
prevent AF from hunting and u can snap even if focal point is not achieved with the lens on AF mode. [ better if your lens allows FTMF ]

reduces number of presses on shutter button [ to hunt focal point ], thus lengthening lifespan of that button [ which is prone to fail always on canon xxD bodies ]
 

rhino123

Moderator
Staff member
Sep 1, 2006
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#9
help u to af when u are on live view mode
Which camera brand are you using? My Canon focus as per normal even when I am using the live view.
 

Zackt87

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May 26, 2009
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#10
Ows? My camera doesn't need that button to AF in LV mode.

The specific function of that button will vary from manufacturer to manufacturer, then also in what mode you are in and if you set anything custom in the menu.

If you can't figure out a use for it, maybe you don't need the manual controls a DSLR can give.


Which camera brand are you using? My Canon focus as per normal even when I am using the live view.
Flickr: Discussing Live View autofocus problem in Canon EOS 5D Mark II

Canon 5D Mark II: Live View - YouTube (06:17 onwards)

Im using 5D2; AF-quick mode
 

Verticoastro

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May 7, 2006
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#11
All my old 5D and 1Ds are set to back button for focus... mainly for easy lens manual override the and to overcome focus hunt. other then that I can depress the shutter anytime without the lens trying to focus thus missing the shot... but you have to practice and get use to it...
 

weeloong

New Member
Jan 4, 2011
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#12
Many thanks to all who have shared their exp and useful knowledge! =)
 

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