Wed Dec 13, 2006 8:20 pm
I mostly agree with Talley regarding dpi, or more accurately pixels per inch (ppi). For people working with web images or home printing leaving your resolution as it came out of the camera is the right way to go. Inkjet printers are more than happy to work with a 72 dpi image (windows ), (I think 81 is the Mac standard). I have blown mine up beyond A3 quite happily with stunning results. The key is simply the more pixels the bigger you can print without blockiness or jagged edges. Even my old Fuji at 2.4M pixels could manage A3, though sharp edges were jaggy close up, but from a few feet away quite acceptable. Modern cameras of 8 and 9M will no doubt blow up to A1, but I can't afford the kit, not yet anyway.
Commercial offset printing is very different and involves the manufacture of plates. For this reason printshops are very fussy about their image resolution, which is dictated by halftone screen frequency. This is complicated unless you are familiar with it, but generally for colour work this means that resolution works out at around 300dpi, but is dependant on the settings of the equipment and will vary slightly depending on who you go to. The printshop you use will tell you what they want.
Regards John