Sonnar/Jupiter 85/2 lens peculiarity

[Pherdinand]

One interesting thing I've noticed last time while looking up DOF for some lenses.
The Jupiter-9 85mm f/2, aka sonnar or any similar lens, at closest focus possible (1.15m i think) has a DOF around the focus subject numerically almost exactly equal (in cm) to the aperture used. That is, at f/2, DOF is 2.03 cm; at f/2.8, DOF = 2.88 cm, etc, up to f/22 where still the deviation is very small (23.2 cm)
All this based on the web-DOF calculator http://www.dofmaster.com/dofjs.html

I've found it pretty cool, just thought i'd share it.

 

[RML]

Don't you have anything else to do, Csab'? 🙂

 

[Pherdinand]

I do, i do...just a coffee break post🙂 before playing some table-tennis🙂
I was just trying to compare the 50/1.5 and the 85/2 w respect to their DOF, which one can achieve thinner DOF...that's when i've noticed this funky coincidence