You are never, ever going to need 600 ppi in a print, max would be: 420 ppi for 1440 dpi inkjet 350 ppi for highest quality offset printing 210 ppi for 720 dpi inkjet It's real simple, mutiply the ppi (pixels per inch) desired for the printer (you always figure from the printer, if you don't know how it is going to be printed I'd just go with 300ppi) X the print size = number of pixels required. If your scanning, just scan to get the right number of pixels. Forget about everything else, trust me, computer images are composed of PIXELS, there are no actual inches stuck in there, anywhere! PPI and inches are just a ratio derived from the pixel count, many get confused here.