I do agree with Gareee on this subject. Not about Maya and Lightwave thou, their renderers are far more faster than the Firefly, about 8-10 times (Ive tested it many times, well, not tested really, used them instead). They also do not share Poser5s problem with using your computers RAM. But why should you use a rendering engine who are about 12 years old? Why on earth would you satisfy yourself with the few material options in Poser 4/4PP? Maybe because you do not have enough RAM in your computer, thats a legitimate cause, not enough CPU is too. The latest 3d-geometry and textures do take a lot of resources, so do the rendering engine. A not legitimate cause (I think) is because you do not want to learn the few changes between P4/P5 or Its much faster with P4, then (I say), you do not really care about the result!