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How can I go about testing color negative film using the zone system. First, I a m wondering how to check for the proper film speed. Can I do this by finding a . 10 exposure with a densitometer? What is the Zone VIII density I should strive f or with color negative film?
To determine negative film speed I use an ISO that produces a 0.10 density unit above film fog for the red reading only. You do not have to worry about the Zone VIII placement for setting the slope of your characteristic curve. This is because color negative film is developed at its maximum contrast at 3:15 at 38 dc. This is, if you increase the development time or exposure time the curve will not increase in slope. The curve will move up evenly from toe to shoulder increasing in overall density, but the slope will not change (which means you cannot do expanded development like you can with B&W films). So determine your film speed as noted and develop normally and measure your Zone III density and that is what is supposed to be.
I have developed a complete CC for Kodak Pro 100 negative film and found it could record between 10 and 11 stops with almost a perfect straight line CC. This is amazing because I have never seen any B&W films perform this well. I have also been very successful at doing N-1 and N-1.5 contracted development without color shift instability. At N-2 instability was noted but whether the human eye could actually detect it, I do not know because I never did any field work at N-2. Unfortunately, Pro 100 has been discontinued and replaced by Portra. I will be testing this film and the Fuji negative films this winter. I pray that they can perform as good as the Pro 100 has.
Hope this helps.