Several years ago, Kodak opened a new emulsion coating plant for some of its films, including Tri-X,which is one of its oldest, most-honored films. It’s also one that I’ve used as my primary 4×5 film for more than 30 years. It has been a great, reliable film, with wonderful leeway for both increasing and decreasing inherent contrast of a scene, so it has served my purposes well.
Kodak asked if I would be willing to test the new film in comparison with the film they had been coating at the older facility for years. I agreed to help. So they sent me two boxes of film—both unlabeled—so that I would blindly try to note the difference between the two films. They also gave me detailed instructions on how to test the films.
The funny part was that the instructions Kodak gave me would have negated the means of determining the difference between the films, for they suggested developing one of the boxes in one fashion, and the other box in a different manner. That would have introduced a second variable into the testing, making it unclear if any difference between the two boxes of film was the result of the films being different or the development being different.
So I discarded their recommendations. Instead I loaded two film holders—one with film from Box A and the other with film from Box B. I also loaded a third holder with the Tri-X film I had recently purchased, with the idea of triple-shooting any scene I wanted to shoot, developing all three exposures together, and seeing which unlabeled film matched the film I was using, and which didn’t. (Of course the box I had purchased was still from the older, existing coating factory.) By doing it this way, I could clearly tell which box was produced at the old plant and which was produced at the new one. (The differences, by the way, were minor, but apparent, and it appeared to me that I could have continued using the film without even compensating for any changes.)