There are two reasons I think image quality matters...
1. A generally sharper image in good light would have more clearly delineated the DOF. It just makes it easier to assess the image.
2. In a very general sense, many here have been here a long time, and over that time have seen dozens if not hundreds of "camera focus error" threads.
And I suspect most have, like me, noticed that images taken in similar situations, with complaints of focus hardware problems, more likely than not turn out to be operator error. It is purely a statistical thing. And remember, we do not know you. You are relatively very new here.
Now, you have a very difficult swim against a roaring current if you are trying to convince anyone that you have a camera problem and that problem is a fundamental design problem shared by all D7100's.
That leaves only one possibility: If you believe your specific camera has a problem then I'm not sure why it is important that you get "group confirmation" on that. Send it in for repair. Perhaps after doing my "Stop Sign Test".
You are fully convinced that your expertise is such that you cannot be doing anything wrong. That only leaves one of the two options above, I think?
I'm just trying to come to some conclusion here without going round and round with what has already been said. I'm really trying to help, as is everyone else participating here.
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