It's not about the distance scale, there is always a way to estimate. The question is rather: where is your Near Limit? Which object close to your cam still needs to be sharp? But as you can see from my results: there is no need to focus on this point, focusing further into the distance still gives sufficient sharpness. Maybe you redo your Maths and compare with the links provided?
Noted, Octarine. Sorry for mispelled your name in the previous post. ;p