[jychang]

Have you ever stopped to think about HOW MUCH wider the DOF is when you stop down on a DSLR? Because when it comes to macro, the answer is "usually not enough", even at f/22. And at such small apertures, diffraction becomes a big issue.

This is why focus stacking exists for macro on DSLRs, as when using a true macro 100mm lens you basically have only a thin sliver of usable DOF at reasonable apertures.