http://www.schneideroptics.com/info/depth_of_field_tables/ This is for cameras, not sure if it works the same for poser. I haven't tried, but I think to use these you'd have to change the measurement in poser to feet and the focal to the appropriate mm. If python doesn't see anything but PU, then I guess a conversion would be in order. Is that possible with any accuracy? There is an equation, but that's in the realm of physics and I swore off that after college.:) This definitely a thread to watch.