Quote Originally Posted by mpålsson View Post
Dear All,

Over the past few months, I’ve been slowly working my way through Phil Davis’s Beyond The Zone System. Recently, I’ve completed a few film density tests according to his instructions in Chapter 6. I used BTZS tubes to develop TMAX 100 sheet film (exposed under my enlarger’s light in a contact printer with a Stouffer 4x5 step wedge) in XTOL 1:1 at 20C.

I developed the first set of sheets at 5’35”, 6’45”, 8’, 9’30”, and 11’15”. But these times were evidently too short as all the curves were too flat to correctly position the ISO triangle on the 0.1+BF IDmin line. So, I ran a second test with longer times (9’30”, 11’15”, 13’30”, 16’). This time I was able to position the ISO triangle on the IDmin line correctly, and it came out to be very close to the 13’30” curve.

Overall, I’m a bit surprised. Before reading the book, I just developed the film according to Kodak’s data sheet, which recommended 9’45” for sheet film processed in rotary tubes with XTOL 1:1 at 20C. As I recall, Kodak says their normal processing times yield a contrast gradient of something like 0.56. But according to my most recent test, the same time would only yield a contrast gradient slightly over 0.36.rice purity test

Another point of intrigue is why the curves don’t accelerate upward parabolically as the book’s examples appear, but instead seem to be flattening out, or at least stabilize linearly at a lower gradient in the highlights than the mid-tones. I’ve attached my hand-plotted chart below.

So I’ve decided to reach out to the community hoping someone might share their experience. Have I done something wrong in my tests, or do my results seem reasonably accurate? Why such a difference then between Kodak’s recommendations and my tests? I guess I might not have been agitating the film as intensely as Kodak expects, but I felt like I was always agitated the film pretty decently, keeping all the tubes rolling constantly throughout. Anyway, anyone who could offer some advice or share their experience would be most appreciative!

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It sounds like you've done a thorough job with your film density tests! Your findings regarding the contrast gradient differences between your results and Kodak's recommendations are intriguing. It's not uncommon for personal processing techniques, like agitation, to affect the outcome significantly.
Have you considered varying your agitation style or frequency? Sometimes, more consistent or vigorous agitation can lead to different development results. Additionally, environmental factors like temperature stability and even the chemistry's freshness can play a role.
It might also be helpful to compare your results with others who have used similar setups. Sharing your hand-plotted chart could encourage feedback on the curve shapes you're observing. Keep experimenting, and I’m sure you’ll get closer to the results you’re aiming for!