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Archive 2013 · Help with 7D AF settings (BIF)
  
 
RogerC11
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p.1 #1 · p.1 #1 · Help with 7D AF settings (BIF)


I am having some trouble with getting a reasonable of in focus shots for BIF. The two shots illustrate some of the types of difficulties I have been experiencing. I had the the Servo speed set to slow for these two particular shots using center point with expansion on. Curious as to how I could change my AF settings to get me a better percentage of in focus shots. (aside from my lack of skill)

400mm
f/6.3 ISO 800
1/2500th









Feb 24, 2013 at 07:13 PM
Pixel Perfect
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p.1 #2 · p.1 #2 · Help with 7D AF settings (BIF)


It appears that the 7D has back focused, as the water is sharp behind the bird. I assumed you placed the centre AF point over the head of the bird, but it's a fairly small target and of low contrast. The AF may have then shifted to a surrounding point even if servo speed was set to slow as it could not obtain focus with the chosen point.

One thing that would be interesting is to open the image in DPP and use shit + L to see where the focus point was that achieved focus. If it's on the water you have your answer.

Apart from adjusting the AF settings it may be a case you need to pump the AF to try and achieve a lock if it's struggling with the low contrast subject. Try releasing and re-enaging the AF or try a different spot on the subject. Birds coming straight at you can be tough especially an all black or white bird.

Other things to try in this case are using single point rater than expansion.

What were your other AF settings under CFn III?



Feb 25, 2013 at 01:16 AM
RogerC11
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p.1 #3 · p.1 #3 · Help with 7D AF settings (BIF)


I have been reading up on some AF settings used for 7d BIF and I have not tried the pumping AF technique you mention yet but it seems to have good results. I will try it on my next time out. In this case, I just held the AF point on the bird hoping the 7d would keep tracking. My relevant CFnIII are as follows:

1: slow
2: AF priority/Tracking priority
3: Continuous AF track priority
4: Focus search on
7: stops at AF area edges

I have also separated the AF from the shutter and moved the AF start to the AF-ON button.



Feb 25, 2013 at 02:23 AM
 

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lighthawk
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p.1 #4 · p.1 #4 · Help with 7D AF settings (BIF)


I notice when I shoot my dog running directly at me that she will outrun the focal point, creating a back focused shot. I'm using a 7D, mostly with a 70-200 for this application, although I've seen the same result with 400/5.6.


Feb 25, 2013 at 02:49 AM
ashley138
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p.1 #5 · p.1 #5 · Help with 7D AF settings (BIF)


I think that for a subject coming fast directly at you, the 7D just doesn't always have fast enough AF - at least this is what I've gathered from from stuff I've read and some personal experience. The newer 1D bodies should be fast enough but not sure how to combat this issue on the 7D. If your having this problem with subjects moving parallel to you, then maybe you have a back or front focusing problem.
I think your settings are fine - I wouldn't think that is the problem.



Feb 25, 2013 at 03:10 AM
uz2work
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p.1 #6 · p.1 #6 · Help with 7D AF settings (BIF)


RogerC11 wrote:
I am having some trouble with getting a reasonable of in focus shots for BIF. The two shots illustrate some of the types of difficulties I have been experiencing. I had the the Servo speed set to slow for these two particular shots using center point with expansion on. Curious as to how I could change my AF settings to get me a better percentage of in focus shots. (aside from my lack of skill)

400mm
f/6.3 ISO 800
1/2500th



Your settings look to be fine, but you need to be certain that you have locked in focus with the center point on the bird before you start shooting, and my guess is that that did not happen. The 7D should be more than capable of doing well with AF in that situation. I have many bursts of 7 or 8 shots of a bird flying straight at the camera with busy backgrounds and ending up with 7 or all 8 of the shots in focus.

In your pictures, I'd be fairly certain that the focus locked on the background. With the relatively small head of the bird, I would not even try to focus on its head. I'd try to lock in focus with the center point on the fat part of the bird's breast, and there still should be enough depth of field to keep the head in focus. Also, as Pixel Perfect suggested, if the amount of contrast is not sufficient to be able to lock in focus on the bird, I would switch to just using the center focus point so as not to allow one of the surrounding points to lock onto the water. Again, though, regardless whether you are just using the center point or the center point expanded to surrounding points, you still need to start by locking the focus in with the center point. Until you have done that, the camera doesn't know what the subject is on which it should be focusing. And, as soon as you sense that you are starting to lose focus, that is when you need to back off of the shutter and re-establish focus lock, again, with the center focus point.

Also, even though I don't think that it is the cause of your out-of-focus shots, my preference is to leave the tracking sensitivity at its default neutral setting. That setting is a double-edged sword. If you reduce that setting, it should theoretically make it less likely that you would lose focus, but it will also make it less likely, if focus is lost, to regain focus. Similarly, if you increase the tracking sensitivity, it can make it more likely that focus will be lost while tracking, but it will also make it more likely that focus will be regained. My experience with multiple 1-series bodies and with the 7D, however, is that this setting is rarely the reason for either success or failure in tracking a moving subject, and, unless there is some specific reason for changing the setting, I leave it at the default.

Les



Feb 25, 2013 at 03:47 AM





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