+ 1 for Dan
+ 1 for Ralph
(I will read the Staler after brunch)

Over the years, I have "collected" ZS interpretations for those who are more interested in taking good pictures than proving their maths proficiency. Among my favourites is one from Gem Singer, over at lfinfo, which is almost as good as the ones above. (but lacking the distinction of the "important" details in the shadows and highlights) There is also an equally brief but slightly different one by Rob Gray, and a rather irreverant one by Jim Brick that reduces the zones to four, "Zone Good, Zone Bad, Zone Ugly, Zone Butt Ugly." His treatment gives a bit of a chuckle, but his reasoning is sound.

These three are posted on my site (with permission of the authors)