Hi Tom,
I noticed the same thing. When I was young I used a Lunasix for many year with my pentaprism Nikon F. Recently I bought a Lunasix F on Ebay (out of nostalgia - it turned out to be defective, but that is another story and don't want to annoy you). Before the purchase I got the manual in English in the web and I read it all included the part on the zone system.
So I turned to one of my books, Steve Simmons' Using the View Camera AMPHOTO), where one can find a decent explanation of Zone system.
Quite frankly the zone system is for those lucky photogs, that develop and print all by themselves. Otherwise it is of little utility and the concepts reduces to the ten stops range of tonality. In fact if you read an area with a spotmeter and set the exposure by the reading then (by the way the meter is calibrated) if nominal values were true (the ISO of film developing and printing process) that area would go to ZONE V or medium gray. Because in practice the assumptions are not valid, one has to find its own ISO by experiment until this happens precisely.
From this I see that the system is not for me. I do use a spot meter and decide what goes on ZONE V by setting the corresponding exposure and... crossing my fingers. Then I take a lot of contrast measures too check how many stops below are each shadow and highlight, possibly rethinking the exposure if I am not satisfied by the contrast readings. In the end if everything goes well (and in extreme cases bracketing can give more robustness to the procedure) possibly with some corrections in Photoshop, I can get satisfactory results.
Hope will help
Cheers
Paul
