Some time ago I printed on see-through fabric and the printer guys said they only needed 10 Mb per square meter! That was approx. 43 dpi. When I saw the output it was crisp and clear, even the logotype I put in, the letters having harsh lines. But it hints to another connection to the 'naked eye' thing Impudicus mentions: The larger the output, the smaller your image resolution (and print resolution) can be. I am certainly no mathematician, nor very good at it, but at some point there must be a balance between resolution and how large the output is, which has to do with the fact that nobody looks at a 70x100 cm poster at the distance one looks at an advertisement or book cover. So the further away you look at a printed medium, the lower the resolution can be. Something like: Image resolution = 300 divided by (looking distance in cm divided by 30). Oh no. I shouldn't try anything like this. This understanding helped me through several nights wrestling with 900 Mb layered Photoshop files on 200 dpi which were impossible to work on (on a Mac G3) when they were 300 dpi (the night before). For 70x100 cm posters 200 dpi proved to be enough. Only if you stand too close you will mention some lack of detail. Detail you won't see after all if you look from the proper distance. Mmm. Not a real addition to this thread. Just that it helped me a lot to discover that I can make REALLY large stuff on my computer. Because of the human eye and clever interpolation of modern printers as well.