Quote Originally Posted by ic-racer View Post
Like I posted previously, with the larger format your depth of field will be less and if you try to correct with a smaller f-stop your results will be limited by diffraction.

The reason your depth of field will be less is because you are focused CLOSER to the object (in terms of film format diagonals) with the large format camera. All else being equal (ie subject size, subject distance, final print size, absolute aperture 6mm or whatever, etc).

Indeed with pictoral subjects, the depth of field is nearly the same between large and small format cameras when absolute aperture diameter is the same. But once you move in close, you are going to need to increase your subject size to maintain this relationship

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.