We had a very long discussion about DOF here… Physical Defocus
I can recommend frischluft.com - Lenscare Description …well worth the money and the only way to really get DOF correct for 3d rendered assests with a z-depth matte.
Have a good read through the link on the forum, I think I went through everything. I used the LensCare matchbox on the robot job and it did an excellent job.