Don wrote this:
"Think about this for a moment, if you will. If we test and establish that a film such as TriX, for instance, is truly a EI 160 film (based on a .10 density in HC110 dil b). Then we place the low values in an exposure on a Zone III or IV. Aren't we in effect saying that irrespective of the manufacturers rating or Ansel's and Fred's edicts that this film needs to be exposed at EI 40 (Zone III placement) or EI 20 (Zone IV placement). Then when we have in our development testing placed our high value densities at 1.25 above FB+fog we have in effect shortened the entire scale of the film. This is a sure guarantee for flat and lifeless prints in my darkroom."
Lee wrote this:
"the way I interpret this is that the zone III is really at 80 and the zone IV is 110. Maybe I am not understanding properly. Certainly would not be the first time.
If one is slavish to the zone system, one can expect some of the problems that Don has stated. I disagree with the number he used for zone VIII. I like 1.35 for zone VIII. The 1.2 or 1.25 would be about zone VII in my book. I use PMK pyro and without a color densitometer I can't tell exactly what the zone really is but I have exposed and developed and printing a lot of those negatives. My times do not reflect what Gordon H. uses or recommends.