I'm hoping some of you accomplished LFers can sort out a disagreement I have wit h a fellow photographer that goes to the basic foundation of large-format photog raphy. It's kind of hard to explain, so forgive me if this sounds a bit convolut ed and long-winded. Here goes. . .
My contention is that LF depth of field technique is basically the same as that which I have used with my Mamiya RB67 (pick a composition, select an aperture th at'll render everything I want in focus), except that with my LF I can use movem ents to "enhance" or "alter" my DOF on images that need more depth than simple a perture selection can attain. I know how the Scheimpflug principle works. My fri end, on the other hand, says that I should always use movements first, not only in terms of order of application in the field, but from the very start of the co nceptual process. Here's an example that I used on him to stress my point, and h is reply: I'm shooting two cottonwood trees, one is 75 feet away, the other is 1 00 feet away. I know that with my 210mm lens, if I focus on the closest tree and use a relatively small aperture, say f32, that everything from that tree to the horizon will be within the zone of focus. (Assuming, for argument's sake, that the tree at 75 feet isn't quite at infinity, but close.) Or I could even focus a little beyond the first tree and let some 'front-side' DOF bring it into focus. Therefore, in either case, I wouldn't even need to consider movements.
My friend contends that instead of focusing on the closer tree and stopping down , I should focus on the closer tree and then use tilt to bring the farther tree into focus. Then I can stop the lens down to increase my chances further. My pro blem with that scenario is that the tilt will not increase the DOF unto itself, rather it will only change the *plane* of focus. I would therefore have to worry not about being in focus from one tree to another, but instead, from the bottom of the tree to some point *above* my new plane of focus.
Furthermore, he argues that he can get much more DOF out of a 210mm lens on his 35mm camera than a 210mm on LF. MY argument is that both lenses give exactly the same DOF (DOF is DOF is DOF, etc.), but the LF lens covers a wider angle of vie w, so objects that aren't even in the frame of his 35mm shot will need to be rec koned with in LF. I am certain that if we shot in the exact same direction with the same focal length (him on 35mm, me on LF), I could crop a 24mm x 36mm frame out of my 4x5" shot, lay it side by side with his 35mm image, and the two would be exactly the same (discounting slight variations in lens quality and other su ch peripheral factors).