the problem with photorealistic renders in poser, is the rendering engine. by increasing the render resolution and changing the camera focal to 400mm as opposed to the 35mm default you improve the final render. or, do as most people do for better renders, use a raytracer to render, vue d'eaprit and bryce are both popular for that..rendering poser scenes. they are terrain generators, so have realistic volumetric lighting, which poser lacks.