Normally, offset-printing is done either at 60 lpi (lines per inch) or 70 lpi. For 60 lpi you need 305 dpi (dots per inch) resolution, for 70 lpi you will need a resolution of 350 dpi. Do not hit to high on the dpis, or you may risc getting a moire-pattern in your prints. If you are aiming at a mathematical-raster-print, you'll need your pictures at about 400 dpi - the rest will be done by the RIP-software. You should render the image at maximum resolution possible in Poser (4096 x 4096 pixels) and cut and resize it to fit your printing-size + 3 mm on all sides (bleed) When converting from RGB-colours to CMYK, make sure to use a solution for art-prints or else your pictures will look flat and greyish in print. If you need any help in converting the pictures for print, I can help you. I am doing this kind of thing quite a lot.