Originally posted by Yamanobori Not with a 645D with these lenses. The DoF scale is already one stop narrower on the lens. For a given focal length, you have more DoF with a larger format.
I know that very well, but f/16 is seldom necessary. The 645D has only a 1.27x (linearly) larger sensor than 24x36, which equates to an 1.27^2 = 1.6 stop difference in DOF. Not at a given focal length, but at a given angle of view.
The difference between 645D and 6x7 is ~2.6 stops. Which means that f/22 on 6x7 gives the same DOF as 22/(1.4^2.6) = f/9 on the 645D.
Largest possible DOF might be a nice thing, but one should remember that most lenses give their highest contrast and sharpness at about 2 stops down from wide open. So the 120/4 Macro is probably much better at f/8 than at f/16. And then we haven't even considered diffraction, which can be an issue if you want to squeeze the best out of the fairly small 645D pixels.
You might as well get the same softness in the background from diffraction at f/16 that you would have gotten from limited DOF at f/8, while the subject in focus is just as smeared by diffraction as the background. I can't see how that would be a good thing.
So, don't stop down further than you have to!