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Are you looking for a source other than Mpix, or are you just asking how large you can print? If it's how large you can go, consider the viewing distance. I have images taken with my D3s that have been printed at a number of large x huge sizes, including 3 foot by 6 foot, 4 foot by 8 foot, 10 foot by 12 foot, as well as full size billboards. So it's really a matter of the quality of the photo that you start with, the viewing distance, and the medium that you're printing on.