Dev time help, Rollei Paul & Reinhold @ 25ISO, camera default

[moodyblue]

Shot one of the Rollei 100yr anniversary rolls in a Pentax Espio 145 point and shoot, which has a default ISO of 25 (only after shooting did I note the manual saying non-DX rolls should not be used, oops!).

I will be developing with Ilford DD-X @ 20°C. My usual dilution is 1+4 but having a full bottle I can vary this if needed.

Wondering what might be the best development time to make the most of this higher-sensitivity film that was shot at such a low-sensitivity setting?

Any theories and suggestions appreciated!

 

[KitosLAB]

I just wanted to open a new topic but I see that this is a great fit for my post. In the USSR, we often used this method to determine the time of development. So, we cut off a small piece of film and lower half of it into the developer, at the same time turning on the stopwatch. Initially, the wet part swells the emulsion and brightens.
Then comes the development process and the emulsion begins to darken. At the moment when the color on both parts becomes equal, we turn off the stopwatch. We multiply the resulting time in seconds by 3.14 and get the manifestation time in minutes.
I just developed the film. Responsible film, my daughter filmed in Stockholm, Prague and Kyiv. In my case, the time in seconds was 23 seconds. 23 x 3.14 = 72.22. We consider = 7.5 minutes. I played it safe and showed 8 minutes, but now I see that really 7.5 would be ideal. Film Ilford 400 developer Foma, water temperature was unknown to me about 18C. I don't know why, but this method really works and can be used when there is uncertainty. I will be glad to questions, comments and results of experiments

 

[koraks]

the time in seconds was 23 seconds. 23 x 3.14 = 72.22. We consider = 7.5 minutes.

That's a really neat trick, but you lost me on the calculus here. 23 seconds multiplied by 3.14 is indeed 72. According to your earlier statement:

We multiply the resulting time in seconds by 3.14 and get the manifestation time in minutes.

This would result in a development time of 72 minutes. Perhaps there was a small detail missing, and the rule of thumb should have been:

"Multiply the resulting time in seconds by 3.14, then divide this number by 10 and we obtain the development time in minutes"

Would this be correct?

 

[KitosLAB]

That's a really neat trick, but you lost me on the calculus here. 23 seconds multiplied by 3.14 is indeed 72. According to your earlier statement:


This would result in a development time of 72 minutes. Perhaps there was a small detail missing, and the rule of thumb should have been:

"Multiply the resulting time in seconds by 3.14, then divide this number by 10 and we obtain the development time in minutes"

Would this be correct?

It is most correct to multiply by 0.314 and then round up for reliability. But for some reason we multiplied by 3.14 "in the mind" translating into minutes