Above 300 ppi is sort of a waste, but if you have an image with a great deal of resolution and want to print a small size, that's where you are. No reason to interpolate UP to more than that though. There are some terrific digital printing mail lists. These folks make printing an art---most on my b/w digital print list are shooting with film, scanning with state of the art scanners and printing digitally--for sale. They are interested in producing very VERY good prints--and as archival as possible. Then there are several other lists--some printing with just Epsons, etc. If you are interested in getting the best print with your equipment, then I'd advise trying one of these lists. And then, of course, there is color managment LOL---this will ensure a better print also, though has nothing to do with resolution. BTW, Misha, one of the lists has been discussing the relationship between the pixels and the dots.