D800 left - center - right AF tolerance + green LCD

No - I mean test as I suggested

If you re read what I said you will see I mentioned this. In a little more detail the D800 can detect a target about 1/8 in size of the viewfinder rectangle - to outside the rectangle boundary in single point AF.

When using 9 or more point dynamic autofocus detection can be to outside the boundaries of the next autofocus point.

This is why I said the fine detail reference target has to be well away from where the autofocus is aimed.

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Leonard Shepherd
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.