Only if the lens in long enough though - good luck getting any noticeable circle-of-confusion out of a 20mm lens on 35m. It's not just about aperture and focal length either: sensor size makes a big difference as well. My GR-D, which has quite a small sensor and a 28mm wide angle lens, has massive depth-of-field even at f2.8. With the 21mm adaptor you hardly need to focus it, except for macros, while with the 40mm you can get a bit of isolation if the background is far enough away from a reasonably close subject.