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D7100: AF focuses on background a lot?


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doppler_fto

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"RE: D7100: AF focuses on background a lot?"

doppler_fto Registered since 23rd Mar 2013
Sat 04-May-13 05:30 PM

>In looking at 0404 and 0417 one issue may be with shutter
>speed and the movement of the drummer. If you look at his
>waist area and pants I think you will see that they appear to
>be better in focus than the upper body and head which would be
>moving more than his waist. The slow shutter speeds simply
>make it harder to determine if it is the cameras AF system.
>Especially if it is happening with 2 bodies.

The reason his waist is in better focus is because it's closer to the wall which is what's actually in focus. Part of why I added 0517 to this set is to demonstrate definitively that the camera is focusing on the wall, and that the problem isn't motion blur or anything like that.

>The shutter speeds also seem a little low compared to the
>focal length. One of the things that became somewhat apparent
>with the introduction of the D7000 is that in order to get
>crisp images consistently you really need to be at 1.5 to 2
>times the focal length with the shutter speed with the
>increased number of pixels unless your technique and hand
>holding is flawless. I am sure that is even more important
>with the even larger number of pixels on the D7100.

I appreciate the advice, but this is pertinent to the issue at hand. If you're curious about my hand-holding abilities, the following post includes a number of images that I shot handheld at 1/15s with my 80-200/2.8. Remember that the 80-200 doesn't have VR:
http://blog.doppler-photo.net/2008/08/17-hours-of-street-photography.html

>Looking at 1009 I am not sure what happened on that one as it
>is clear that the area in focus is the table behind the guy
>kneeling.
>
>I think I would head outdoors with some good light and try
>doing some tests under those conditions using focus priority
>in AF-C single point and see what you get. If you still are
>having trouble you may have a problem at which point I think I
>would do a little more formal testing using a tripod, etc., in
>order to be sure of my results before contacting Nikon.
>Although, with it happening on both bodies I find that very
>unusual based on the track record of the D7100 so far, but
>anything is possible.

I'm still trying to get a better understanding of which situations provoke this behavior; I don't think I'm anywhere close to having a repeatable testcase yet. In particular, because I notice this when I'm actually trying to cover events, I don't have time to stop and troubleshoot; I just end up compromising on my desired compositions to make it easier for the AF system to do the right thing.

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This is a hot topic  It has been locked by a team member D7100: AF focuses on background a lot? [View all] , doppler_fto , Fri 03-May-13 05:19 AM
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