Originally posted by bossa And the reason there IS a difference is because we then enlarge the output to a standard set of sizes.
And that's presentation, not photography -- part of the picture-making process, but not controllable from the camera, just as we can't control perception.
[rant]
DOF is a complex product of photography, presentation, and perception. We can control the photographic factors: camera, lens, aperture, distances, etc. We *might* control the presentation somewhat: enlargement, framing, placement, etc. But unless we're mind-control wizards, we can't control perception: the viewers' visual acuity, state of mind, hallucinations, etc. So we do the best (or worst!) that we can, and to hell with the circle-of-confusion calculations!
[/rant]
If we enlarge to LARGE (non-)standard sizes, DOF differences between formats becomes noticeable. At small sizes, not. I've mentioned making 6x9cm prints of 1mpx P&S images (810x1216 pixels) and contact prints from 6x9cm negatives, printing them on the same paper, glassing and framing them the same, presenting them side-by-side -- and except with a magnifier, they are indistinguishable.
The moral: Keep the image small and you can get away with almost anything!