A book called, The New Zone System, gave me some ideas to use. I shot a roll of new Tri-X 400 in my Pentax 6×7 of a gray card exposing it at every setting so that I could figure out the ASA. The least exposure was made. A gray card correct exposure was made and a blank frame was made. Then a series of exposures were made in 1/2 steps. Zone 1 is four stops closed from the gray card. I went past 800 ISO a full stop and past 200 ISO a full stop.
One of those exposures would show me the optimal ISO to use the film at. But which one and how was I to determine which one?
More tests were needed. Photo paper was totally exposed to bright light and developed to a maximum black. Another sheet was not exposed at all and fixed as is. That gave me a maximum white sheet. Then wedge tests were made using the blank negative.
A step wedge test was made to determine the time needed to expose paper through a blank negative to maximum black. The enlarger was positioned to make an 8×10 print even though 4×5 paper was used. It was focused on the grain in a frame that had a gray card visible in it. Then the blank frame was put into the negative carrier. The iris was set to f22. Two seconds were given to each of five areas then four more seconds to the entire sheet. That made the areas from right to left to be 6, 8, 10, 12, 14. I can see the 6 and the 8 and sometimes the 10 second areas but no more. When I held up the 4×5 backwards to the light I could see the differences between the first two areas. Scanning the strips like this really shows the changes.
Another strip was made in single seconds to narrow the changes. f22 @ 1-5 +4 seconds overall. 5-9 seconds as shown. Under a lamp I can see all these steps clearly. Of course the blacks in reality go very black but in the scan the differences are pronounced. That helps to determine what is maximum black.
A 4×5 was exposed to light without a negative in the carrier. The idea was to expose the paper and make as black a black as the paper could make. There is no point in showing it here as it only looks gray. A white sheet was also made. The blacks in the tests looks like it. f11 was used for one minuet; it was developed three minuets as were all other tests. The white was only fixed.
The maximum black 4×5 was held up along side of a 9 second exposure 4×5 and my wife correctly chose the darker one. 9 seconds is not dark enough.
10 or 11 seconds is the correct exposure to make maximum black through a blank negative with my stuff.
Any other negative that has any density at all will print lighter at the same time and development. The first one that I can see clearly will be the correct ASA for that film and paper. That is zone 1.
Tri-X 400 film was used as was Ilford MG IV paper. D-76, stop bath, fixer and Dektol were freshly mixed. Dektol was diluted 1:2, D-76 was 1:1. Development of paper was 3 minuets.
The New Zone System Manual book supplied these ideas. Not the scanning of the prints. That is my idea.