I created a makeshift focus chart in order to try testing my camera’s focusing system again. The following photo is a crop, reduced in size by 50% (along each dimension):
As you can see, focus is pretty much dead-on. Yet clearly, in my original review of the Olympus 50mm f/2.0 lens, the camera front-focused.
My best-guess conclusion is that the lens is in spec, and the Olympus E-500 DSLR focuses well when you point it at black text on a white background, but the autofocus is flaky when pointed at real-world objects like bottles of scotch. I will further guess that maybe the problem is that the center autofocus sensor is much bigger than the label, and is also picking up some of the glass, and the optical properties of the glass are confusing the autofocus.
These tests demonstrate the difficulties of using wide-aperture lenses with autofocus DSLRs.