Hi Doug,
in regards to DOF, more to do as to how close you were to the cup, see:
http://www.dofmaster.com/doftable.html
You will see that a 50mm at f/16 on a D70s at a focus distance of 50cm, the DOF in about 5cm, so pretty shallow, gets more shallow as you get closer.
As for your cup, it still comes out nice and clean,
cheers,
André