skiwillgee - i've got a company to ptiny a poster for me in A1 - resolution was 3307 *2339 in 150 dpi (they even say 100 is suitable) - the reaseon it produces a very very nice result is that you will look at a size A1 or bigger at a distance, which means you won't see the pixelisation very much - and i must say that even close up it looks fantastic

/Arne