At the risk of having this thread suffer the same fate, I suggest 2.8 is the number you seek.
Why 'stop' @2.8. That's not fair '2' those more 'open-minded' or those who have had 1.2 many cocktails.
Certainly your DOF gets narrow as you approach 1 . . . then everything goes fuzzy as you're finally able to take it all in, and then darkness as the shutter comes down.
Oh I do like this metaphor. Better than the chicken even, though that did result in me giggling audibly in the office.