I'm not Michael but I'll give it a shot. PJ's right - digital images (from scanner or digital camera) are soft even if the focus is dead on, etc. Sharpening can be done in the camera and/or later in Photoshop. I took the liberty of running it thru Photoshop and giving it some Unsharp Mask - hope you don't mind but I gathered that this is what you were looking for.
These are levels I usually start with (compliments of Scott Kelby's book):
Amount: 125
Radius: 1.0
Threshold: 3
That seems to do the trick to my eye. One thing though, some cameras can have problems with back focusing. Basically, this is a mis-alignment of what the camera thinks is in focus. It's going to be most obvious at wider apertures and shorter distances. Try shooting a ruler near the minimum focus distance of your 50 f1.8, and do it wide open. Focus right on a number and see if it's sharp, or a fraction one way or the other. Put the ruler pointing almost away from the camera so there's some distance involved (just not perpendicular to the camera). If this is the problem, you may want to exchange it - unless you never shoot that way (moderate distances and moderate apertures - say 10' at f8 - will have enough DOF that the problem will pretty much go away).