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I think if you were to get similar results with a superwide camera, you'd need a lens that approximates the angle of view. If he's used an 85mm focal length lens to stitch together a 4x5-sized image, then that should be the same as using an 85mm lens for a single shot on a 4x5 camera. As far as I know there are no 85mm lenses for 4x5 (there are 72, 75, 80, 90, etc), and there are definitely no large format lenses that open up to f/1.2.
But if there were an 85 f/1.2 lens that could cover 4x5 at this focus distance, I would think the DOF would be exactly the same. I mean the format size/CoC, focal length, aperture, and subject distance would be the same.
I'm not sure how far from th car he was, but for a single shot on 35mm with a 28mm lens he'd need a really wide aperture to achieve a DOF like this one. I mean it would need to be below 1.
The f/number shouldn't need to be scaled if you're using an 85mm lens on 4x5, though. The difference between a 4x5 lens and a 35mm lens is mainly the image plane coverage, but for a given focal length the f/stop and focal length don't change.
There would, as you say, be a difference in field curvature with a single shot rectilinear lens, and I'd think that 28mm on 35mm would be fairly similar to 85 or 90mm on 4x5. There may be other differences, because LF lenses cast an enormous image circle to allow movements, so if you don't use movements at all you have basically flawless lens sharpness at the corners of wide lenses. This is true with some wide angle SF lenses, but the sensor/film is much closer to the edge of the image circle on these formats. The LF lenses have a different amount of field curvature as well, depending on design, because they're often a fairly simple symmetrical or near symmetrical design. On the other hand, the stitched 85mm image on SF would be pretty darn flat if you could avoid parallax errors. The only way to get a flatter field than that would be to use a true flat-field lens (like a macro).
Creo que finalmente nos acordamos!