N.B. This is not really a question, but an answer to a year old thread.
Based on a discussion about quality difference in digital printing from 5x7in vs 6x7cm (see Digital threads) I decided, being a scientist, that I should run an experiment. The impetus was conflicting statements about whether there were disc ernable differences between rollfilm and 4x5 when printing to a Lightjet5000 at sizes up to 20x24 (4000x5000 pixels). Bill Nordstrom has said that there would b e no significant visible difference. Joe Holmes said that a 4000x5000 scan from 4x5 would be absolutely sharper than the same resolution scan from 6x7 (or 6x9). Since I have great faith in both of these individuals, I decided I had to run a test.
So, I shot the same scene in 4x5 and 6x9. Both cameras used Velvia, and I select ed a lens for the 4x5 that was 50% longer than for the roll film. The lenses wer e a 180 Apo-Symmar for 4x5 and a 120 Apo-Symmar for rollfilm. The 4x5 was expose d at f/22, the 6x9 at f/16 to compensate for both differing diffraction limits a nd depths of field. The 4x5 was scanned at 1400 dpi, the 6x9 at 2100 dpi. Assumi ng (as everyone seems to say) that the optimum input to the Lightjet is 203 dpi, those resolutions correspond to a print with a maximum dimension of about 30 in ches.
I have compared the resulting scans in Photoshop. They are incredibly similar. T here are no specific details in the scan from 4x5 that are not visible in the sc an from 6x9. However, the edge contrast is slightly better in the scan from 4x5 giving the impression of just a hair sharper image. The difference is very subtl e but it does exist. I doubt that it would be as noticible in a print as on a mo nitor.
I conclude that Bill and Joe are both right. The 4x5 does generate a slightly "s harper" scan, but a moderate size print, say up to 20x30, from 6x9 will be virtu ally indistinguishable from one made from the larger sheet film.
I would love comments or feedback, and am willing to email snippets of the scans to anyone that wants to see what the difference in format means in this digital age.