Why 36MP at 100% looks less sharp than 12MP a 100%

Ok I am going to disagree.

Firstly the circled spots are in the OOF region on both images and therefore it is not a true indication of sharpness to start with- and that will affect the D800 more than the D700 because it can resolve the difference but not blur.

2nd, I really don't see the D800 shot to be sharp as what I have seen and therefore I wonder what lens, what aperture were used ?

To me the D800 looked like an up-scaled D700 image or vice versa rather than from a different camera and since the DOF is so narrow I doubt whether the lens was at its sharpest or whether it can handle 36mp anyhow.

I may well be wrong but I don't see the explanation you gave as being correct because it could be a optical issue (d800 out resolves the lens at that aperture), DOF (it is in the OOF region and blur can't be resolved - only sharpness) rather than sensor issue.

Cheers
Neil
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