Quote Originally Posted by Michael R 1974 View Post
It is worth noting many ZS testers just try to find a net D of 0.1 4 stops below metered without giving more thought to local contrast in the toe. 0.1 above B+F in the context of the ZS is a means to an end, the end being adequate shadow contrast, which is subjective to some extent. A target Zone I density in and of itself is meaningless.
That's a very important fact. The 0.1 Density for Zone I came later. First it was a noticeable difference between blackest black and first detectable tone. Ralph Lambrecht pointed out in the Focal Encyclopedia that later papers were able to reach such a higher D-Max that even the earlier visual match test became unreliable.