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Thread started 18 Oct 2013 (Friday) 09:22
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Should you release Back Button Focus in Servo when taking the picture?

 
travisvwright
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Oct 18, 2013 09:22 |  #1

I'm not doing any fancy sports but I'm using back button focus and AI servo. So i get focus and my subject moves a bit, and I'm ready to take the picture should I release the focus button so that the lens stops moving? Or does the AF automatically pause to allow the shutter? Or is the shutter so fast that it doesn't matter?


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rrblint
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Oct 18, 2013 09:27 |  #2

If your subect is moving, you should keep the button pressed. If the subject and camera are stationary, then release the button.


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GregDunn
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Oct 18, 2013 10:00 |  #3

You want the servo tracking till the last possible instant if the subject is moving. Not sure when the camera stops updating the lens focus, but it doesn't hurt to keep the button down - especially if you plan to take another shot quickly afterward.


Canon 1Dx | 5D3 | 7D2 | 6D | 70-200L f/2.8IS | 70-200L f/4 | 24-70L f/2.8 | 24-105L f/4IS | 100-400L f/4.5-5.6IS | 17-55 f/2.8IS | 50 f/1.8 | 28-105 f/3.5-4.5 | 4x Godox AD360

  
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scotchtape
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Oct 18, 2013 10:27 |  #4

Actually... can I also ask for help?

I've read lots of stuff online and in the manual but I'd like to know how people use AF during event photography, or even for sports.

Does anyone focus / recompose during those events? What about for sports? Do you just select and AF point and then keep the AF point on the subject? How do you do this if you want to recompose the shot... Is that even possible?

The reason I ask is because I've tried focusing with BBF, AI servo on a point, but then I want to recompose. So I do so, hoping that somehow the AF will track the subject across the frame. I guess I often end up with the subject not on a focus point which is why I've gotten quite a few OOF shots. Are you just stuck to keeping an AF point on the subject without regard to composition for subjects in motion?

Just wondering how other people do this - if they even try to focus recompose with bbf and AI servo.




  
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rrblint
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Oct 18, 2013 10:31 |  #5

scotchtape wrote in post #16380563 (external link)
Actually... can I also ask for help?

I've read lots of stuff online and in the manual but I'd like to know how people use AF during event photography, or even for sports.

Does anyone focus / recompose during those events? What about for sports? Do you just select and AF point and then keep the AF point on the subject? How do you do this if you want to recompose the shot... Is that even possible?

The reason I ask is because I've tried focusing with BBF, AI servo on a point, but then I want to recompose. So I do so, hoping that somehow the AF will track the subject across the frame. I guess I often end up with the subject not on a focus point which is why I've gotten quite a few OOF shots. Are you just stuck to keeping an AF point on the subject without regard to composition for subjects in motion?

Just wondering how other people do this - if they even try to focus recompose with bbf and AI servo.

You have to release the back button in order to recompose or else just use One Shot AF.


Mark

  
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GregDunn
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Oct 18, 2013 11:22 |  #6

Focus/recompose doesn't work well if the subject is moving toward or away from you. The camera will stop focusing when you take your finger off the AF button, and if you leave it on, the camera will attempt to find focus again as soon as it thinks it has lost focus (a configurable parameter on some models). This will lead to focus hunting (unless that is disabled, also a configurable parameter) and unpredictable results regardless. Focus/recompose works best on stationary subjects.

I either track the subject with the selected point and leave room for cropping later or in some cases switch to zone focus if the subject is close enough by then to cover multiple points.


Canon 1Dx | 5D3 | 7D2 | 6D | 70-200L f/2.8IS | 70-200L f/4 | 24-70L f/2.8 | 24-105L f/4IS | 100-400L f/4.5-5.6IS | 17-55 f/2.8IS | 50 f/1.8 | 28-105 f/3.5-4.5 | 4x Godox AD360

  
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Should you release Back Button Focus in Servo when taking the picture?
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