''You looking for me''?

I think this shot has really put the D800 to the test?
It was never anything like this sharp when new!This was taken wide open @f6.3,1/400sec. with my Sigma 150-500 O/S APO lens @ISO 6400.Hence the bit of picture noise? I purposely used max. aperture so as to test the A/F accuracy. And I think I can say that I am happy!
Not the best of subjects with the best of light,but a good result!