Would you be willing to help me with an experiment? My thought is this: We can set up a poser cube at the origin, which would be the focus object, then set up additional cubes every 1 poser unit aligned to the axes of the ground plane (x and z). Then, by modifying the f-stop in prearranged steps, we can get a rough estimate of the "sharpness zone" in poser units. If we arranged that data into a tabular format, it shouldn't be too hard to use a spreadsheet to graph the information and come up with a "close enough" mathematical formula to describe the curve. In order to check our results, we could try the experiment several ways. My suggestion is that we would: a. Get the data for 10 separate f-stop values at 35 mm with a set distance frm the focal point. b. Get the data for the same f-stops at 70 mm with the same distance from the focal point. c. 10 renders, same f-stop values, 35 mm, double the distance from focus. d. 10 renders, same f-stop values, 70 mm, 2x distance from focus. That would require 40 renders in all, which could give us a reasonable data set to generate some real relational data. Can anyone think of a reason this wouldn't work? I can probably set the experiment up as a pz3, and host it on my server, so that anyone with a decent connection speed could contribute or try variations I haven't thought of.