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Archive 2014 · back button vs shutter button focus speed difference?

  
 
Wayne Stewart
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p.1 #1 · p.1 #1 · back button vs shutter button focus speed difference?


When shooting in AI Servo, and taking high speed continuous shots, will the camera/lens focus faster, and stay in focus better, with it set on back button or shutter button, or is there no difference?

The situation I'm referring to is when you have something coming toward you at a high rate of speed, and you're trying to keep them in focus the entire time. I have a sequence that I took, at a Supercross race last month, where I was doing just that, and noticed that some of the frames looked slightly out of focus compared to others in the sequence. I was shooting with a 7D and 70-200mm f2.8 IS Mark I and had it set for shutter button focus. I was using a single focus point, with focus point expansion. The riders were only traveling 30-40 mph, I'm guessing, but were coming straight at me.

I recently decided to try back button focus and I'm liking it so far. It just hit me though that maybe part of the reason why some of the pictures weren't as sharp was because of where I had the focus button set, since I was holding the shutter button down continuously.

Here are a few shots from the sequence to show what I mean. The first one was a few frames before the other two, but the second and third are back to back.


Supercross '14-68 by WStew302


Supercross '14-72 by WStew302


Supercross '14-73 by WStew302

Edited on Apr 11, 2014 at 08:30 AM · View previous versions



Apr 09, 2014 at 06:43 PM
RobertLynn
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p.1 #2 · p.1 #2 · back button vs shutter button focus speed difference?


I think that the mechanics of it are the same inside the camera, it is just a differentiation in the button press by the user.


Apr 09, 2014 at 06:53 PM
EB-1
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p.1 #3 · p.1 #3 · back button vs shutter button focus speed difference?


Are you allowing time for IS to stabilize? I've noticed that new back button users sometimes don't wait long enough.

EBH



Apr 09, 2014 at 07:04 PM
Wayne Stewart
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p.1 #4 · p.1 #4 · back button vs shutter button focus speed difference?


RobertLynn wrote:
I think that the mechanics of it are the same inside the camera, it is just a differentiation in the button press by the user.


So if you have it set on shutter button focus, and you have the shutter pressed completely down, it still continually focuses, just like if you had the button pressed half way down, correct?



Apr 09, 2014 at 07:21 PM
Wayne Stewart
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p.1 #5 · p.1 #5 · back button vs shutter button focus speed difference?


EB-1 wrote:
Are you allowing time for IS to stabilize? I've noticed that new back button users sometimes don't wait long enough.

EBH


Those pictures were taken with it set on shutter button focus, not back button, but yes, during that sequence, the IS had plenty of time to kick in before I started shooting.



Apr 09, 2014 at 07:22 PM
jcolwell
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p.1 #6 · p.1 #6 · back button vs shutter button focus speed difference?


I don't think there's any difference in AF speed between the backbutton and shutter button; however, I prefer backbutton because; (i) I can separate the time and place (in subject space) of setting the AF point from setting exposure/taking the shot, (ii) in AI Servo mode, you can 'pump' the backbutton AF to nail a stationary subject a lot easier than using the shutter button (which results in a lot of extra, unintended photos); and, (iii) in AI Servo mode with high fps, you can easily track a subject to get it in focus, before firing up the high capture rate.

If you're holding the shutter button down continuously, it shouldn't make much difference at all compared to backbutton AF, as long as the subject was more or less in focus at the start of the sequence, see (iii) above.



Apr 10, 2014 at 05:24 AM
jcolwell
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p.1 #7 · p.1 #7 · back button vs shutter button focus speed difference?


Wayne Stewart wrote:
So if you have it set on shutter button focus, and you have the shutter pressed completely down, it still continually focuses, just like if you had the button pressed half way down, correct?


Correct. In AI Servo mode, that is.



Apr 10, 2014 at 05:25 AM
Monito
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p.1 #8 · p.1 #8 · back button vs shutter button focus speed difference?


Backbutton focus => much more control

More control => better photographs



Apr 10, 2014 at 05:53 AM
Dragonfire
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p.1 #9 · p.1 #9 · back button vs shutter button focus speed difference?


I always use the Shutter Button when tracking my subject and shooting in Servo and I press the Back Button when the subject becomes static.

Prior to the 1DX, Canon's back button was too small and difficult to use when compared to Nikon.

Nikon's back button is still larger and easier to use.



Apr 10, 2014 at 06:47 AM
msalvetti
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p.1 #10 · p.1 #10 · back button vs shutter button focus speed difference?


Wayne, the other important feature to be aware of is when you disable AF on the shutter button, you still have the option to adjust how the shutter button press sets exposure. You can either set exposure at half-button press, or you can set exposure at shutter release.

When you set exposure at half-button press, it will not change during a burst. You have to lift and then half-press again. Exposure set at shutter release will vary while you hold the shutter button down during a burst, so if you are panning from sun to shade and using Av or Tv, you'll want to set exposure at shutter release.

Mark

Edited on Apr 10, 2014 at 08:22 AM · View previous versions



Apr 10, 2014 at 07:33 AM
retrofocus
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p.1 #11 · p.1 #11 · back button vs shutter button focus speed difference?


I know many photographers who prefer the back button setup for improved focus control. I tried it for a while on my 5D MkII, but I felt more comfortable using focus control with the shutter button. At least for me this works best. I guess it it a matter of getting used to either way. I just never liked to use one finger for the shutter release and the thumb on the back of the camera for AF. Happened recently again to me when I was asked by a friend of mine to take a photo of him and his family with his 5D MKII - the AF was not working first. He had the back button AF activated.


Apr 10, 2014 at 08:01 AM
Wayne Stewart
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p.1 #12 · p.1 #12 · back button vs shutter button focus speed difference?


msalvetti wrote:
Wayne, the other important feature to be aware of is when you disable AF on the shutter button, you still have the option to adjust how the shutter button press sets exposure. You can either set exposure at half-button press, or you can set exposure at shutter release.

When you set exposure at half-button press, it will not change during a burst. You have to lift and then half-press again. Exposure set at shutter release will vary while you hold the shutter button down during a burst, so if you are panning from sun to shade and using Av or Tv,
...Show more

Good info. I hadn't even thought about that.

So far, I'm liking the focus set on the back. It's not quite second nature yet, but I don't think it will take very long.



Apr 10, 2014 at 08:08 AM





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