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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 27 Feb 2013 (Wednesday) 23:39
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Back Button Focusing question?

 
nathan549
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Feb 27, 2013 23:39 |  #1

Ok so i normally use the shutter button to focus but i was playing around with BBF. just want to make sure, if i get focus of an object wide open (say f1.2) then recompose the image to the left or right of my screen, that object will stay in focus and the rest will be out of focus correct?


Canon 60D - 24-70mm 2.8 L II - 70-200mm 2.8 L IS II - Speedlight 600 ex-rt - Broncolor Move 1200L pack + A2L pack + MobiLED flash head

  
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lehmanncpa
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Feb 27, 2013 23:47 |  #2

Depends. If shooting with one shot focus, the focus is locked when the BBF is depressed (not necessarily locked on the subject, but just locked at the focusing distance). Therefore, when shooting wide open and with such a shallow DOF, especially with a f/1.2 lens, recomposing may change the distance to the object and render your intended subject out of focus. The best thing to do is to select a focusing point and lock focus on the focus point without recomposing your image. Use live view if needed.

If on AI Servo, then the subject would be tracked if you are using all your focusing points. Otherwise, if the subject is no longer on the focusing point, then the AF system cannot track the subject.


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tonylong
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Feb 27, 2013 23:59 |  #3

At such a wide aperture/narrow depth of field, set your AF to an "outer" point that will "match" your final composition and only "recompose" the bit to get the proper framing/composition. You will typically not use center point focus (unless you have no choice)...if you do have to use Center Point AF then, well don't recompose!!


Tony
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nathan549
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Feb 28, 2013 00:12 |  #4

Thanks guys makes more sense now!!


Canon 60D - 24-70mm 2.8 L II - 70-200mm 2.8 L IS II - Speedlight 600 ex-rt - Broncolor Move 1200L pack + A2L pack + MobiLED flash head

  
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Back Button Focusing question?
FORUMS Photography Talk by Genre General Photography Talk 
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