>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.
>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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