Here's the expanded commentary from our video Top Ten Things That I wish I had known when starting in Large Format Photography. For some reason that I don't remember, we started with number 3.
We've received numerous requests for recommended processing times when using our SP-76EC developer with films other than Foma. If you think this is easy to answer, just look at some of the data on popular "recipe" sites. It's not uncommon to find a given film/developer combination listed multiple times, each with a wildly different processing time. Why?
The answer is simple: there are just too many variables. Start with your exposure meter, just how accurate is it? And how precise and consistent are you at using it?
Then, how far off is your shutter? Unless you've just had it calibrated, it's probably further off than you'd expect (our testing shows +/- a stop to be common).
Ignoring these variables, and let's be honest, most of us ignore them most of the time, the next question is: how do you like your negatives? Some photographers like a "thin", almost clear negative; others like them so dense you can barely see through them.
Next comes the question of contrast, do you want a flat negative or one that pushes the dynamic range of the film? Obviously, contrast is highly dependent on agitation and not just how often/how long but to some extent, how violent you get during the process.
What all this rambling comes down to is that unless you can duplicate the exposure and development exactly and then measure the results, using someone else's recommended processing time isn't much better than a random guess.
We've attempted to remove as many variables as we could with our testing of Foma 100, 200 and 400 films (with SP-76EC) and have published our results here: https://shop.stearmanpress.com/pages/film-data-foma
Obviously, this doesn't really solve the problem of all those variables we just listed above. However, it should give you a good starting point for your own testing.