Originally Posted by ic-racer
A bellows, extended, say, 130 mm. On it, a 16 mm Luminar, stopped down 2 stops. A 35 mm camera on the rear.
That produces a magnification of about 10 times, with the DOF and diffraction that comes with it.
Now that same setup, but with a 6x6 camera on the bellows, with the bellows extension reduced to 'compensate' for the longer camera body.
Result: same (!) magnification, same (!) DOF and diffraction.
But on a larger (!) format...
That's the aformentioned 'magnification driven' approach.
But yes, if you want to fill the frame the same way, no matter what format is used, you need more magnification (= less DOF) using a larger format.
But for the reduced DOF you also get increased detail.
So it's not all bad at all with large(r) formats, even when using the "frame driven" approach.