TriX wrote:
All except #3 unless you really need that much DOF. On a DX (crop ) body diffraction starts to rob you of sharpness by f11, and the loss is noticeable by f15/16. I’d try not to go past f8 unless you need to for DOF, and rarely go beyond f11 at the most.
I don't think your sensor is causing diffraction, I think it's probably your lens.