Luminous Landscape have done some comparison tests of 11 professional cameras with huge megapixels such as Phase One P45 (39 MP), Phase One P25 (22 MP), Canon 1Ds MKII (16.6 MP), and Canon 5D (12.7 MP).
“So if we have a close race between a 39MP back’s files and a 4X5″ drum scan, where does that leave us? A traditional enlarger made print can’t hope to compare, and so we now appear to have a new ball game, with top-tier medium format digital close to equaling 4×5” large format. And to my eyes images from the 16Mp Canon 1Ds MKII are awfully close to those from drum scanned 645 format Velvia. “