Thanks guys. I was excited to see so many replies by only 930am! So just to make sure. To get the same framing for different focal lengths the subject distance is proportional to the focal length? (50mm-5ft, 100mm-10ft, 200mm-20ft, 300-30ft, and on and on (even in the reverse direction?)) And just to throw another wrench in the machine. I have the 100mm f/2.0 and the 300mm f/4.0. This is even another question, but I guess I can calculate it now for sure granted the subject distance assertion is correct.