Quote Originally Posted by Stephen Benskin View Post
The Zone System doesn't have one.
So the Zone System defines its benchmark log-H point in terms of the EI which corresponds to the "desired" shadow density quality, which in early versions was a visual determination where you could just detect detail difference between Zone 0 and Zone I on the print.

So many of our variables and constants are not defined... but might be inferred if the components could be isolated somehow... Say by doing flare tests and film sensitometry and working backwards to the same meter settings.