Zone System testing uses a different method than a sensitometric approach using a step table and curves. It states the 0.10 fixed density is four stops below the metered exposure. This method will generally generate a 1/2 to 1 stop slower film speed than the box speed because the ISO speed point is 3 1/3 stops below the metered exposure point (Hg/Hm = 10). Zone System users end up rating their film one half to 1 stop slower than the box speed without any complaints. In fact, most have no idea they are using erroneous speeds because most didn't have a way to confirm their results
Very enlightening. I had no idea Zone System could shift the Film Speed so much.
I'm just reading Adam's books again: The system gives you a tool to make this decisions reproducibly and defines a usable baseline, it is not scientific standard of some kind and was never intended as such. I uses the scientific basis of sensitometry and densitometry as its foundation but in application is was meant as a practical approach, regardless of what some may make out of it.
That is also my understanding from the Zone System, and I am also in the process of reading the books. Ansel Adams makes it quite clear, it is a tool to allow the artist to transform his vision into a final print, and there are scientific but also very practical steps.
I will start with the suggested manufacturer ISO Speed, and see if I find the necessity to make it slower or not. And adopt that as my EI.
Now, I was trying to measure Density using my SpotMeter. This really didn't work at all, probably because it would require a Close Up Lens adapter which I dont own for close focus.
Instead, I have placed an order for a X-rite 331 Densitometer, Second Hand of course, and I will be continue my journey into sensitometry as it arrives. It should be well calibrated, and there will be no guess involved