I picked up an EF to m43 adapter with a built in aperture some time ago. It works reasonably well, I don't notice any vignetting with the lenses that I use it with. I've yet to test how much extra dof I get from it. Controlling the aperture of the lens directly would be nice, but with a price tag in the hundreds, I could pick up some Canon FD lenses (mechanical aperture) and adapt those instead.