"4000x4000 with 300 dpi" = 13 1/3 inches square "4000x4000 at 1200 dpi" = 3 1/3 inches square Render at a sufficient size in pixels to give the size of output you want at the resolution your printer supports, you can set the resolution in Poser or in your image editor - it's just an output scale factor, nothing to do with image quality as such. For a high end item like a dye-sub the manual or the manufacturer's website should recommend values - if it can put 24bit colour on each dot (which lasers and inkjets can't) then you could go up to the physical DPI; you'll probably get best results with a value that is a divisor of that.