I would be curious to know why you would need to render that high. First off, you wouldn't actually be gaining enourmous detail. Second, you can re-rez images up higher in Photoshop. Logically, you could output at 4K in Poser, do the necessary posting in Photoshop- as the image WILL need it, and then rez it up. If you are attempting animation at this resolution, you are totally using the wrong software, as Poser is not (at $179 or whatever it sells for) a high-end professional Hollywood animation program.