None of the above are actually correct. This problem (bug) has nothing to do with the general optimisations, memory utilisation, raytracing or polygon subdivision. I've mentioned this in the SR1 beta forum (link at the page banner above) and I'm trying to reproduce it accurately. At the moment I have one scene with a single light source and a single (one-sided) square, no shadows or raytracing which shows some degree of 'rendering hit' (about an 18 minute render on a 2GHz machine) at certain camera positions. If I have time I hope to put up a bug report and get a pz3 to CL. In the meantime it could be worth looking at whether your problems are due to the camera proximity to a square, or similar object (maybe a backdrop prop) and see if deleting it will help. Bill