Originally posted by RyanW The example about wanting to maintain shutter speed and dof - well sometimes. I would say for many maintaining shutter speed is more important than maintaining dof because unless you are shooting with shallow dof for artistic purpose and I'll agree there are times you will do that. Otherwise, when dof is not maintained, it gets greater not shallower and that's better for landscape, group photos and a whole bunch of other photography.
You haven't understood what I said. I said keep the same shutter speed, use a smaller aperture on the large-sensor camera, and increase ISO to give the same exposure. You will have the deep DOF you want, you will have the shutter speed you need, and you will have the same amount of noise, on both the small camera shot and the large camera shots.
Originally posted by RyanW If it was like full frame I would own m4/3 in a heartbeat because I want the DOF at faster shutter speeds.
No problem, keep the fast shutter speed, and stop down the aperture on your camera, you will get the same DOF as a m4/3. The bigger problem occurs if you want to get very shallow DOF on m4/3, because you have to buy a really fast and therefore expensive lens.
Originally posted by RyanW The equivalence argument seems to think that I always want the same DOF
Not at all. Equivalence is simply a formula for comparing the output of cameras that use different sensor sizes. It will show you what settings and gear you need in order to take the photo you want, with the correct DOF, AOV, SNR and perspective.