How do we get to the bottom of this in order to establish whether stand development has delivered correctly coloured negs? Otherwise we are condemned forever to have members come up with allegedly sound processing methods which involve less than 100F and others replying that at less than 100F colour crossover is inevitable.
Hi, I don't think that this is an argument that "needs" to be won, one way or the other. In my mind, there is very little possibility of a normal person getting optimal "correct" color from an out-of-spec C-41 process. But if someone else thinks they are doing good work with "stand development," or whatever, what difference should it make to me?
To me, the only pertinent point is with regard to people READING about such things, and perhaps being persuaded that such out-of-spec operations are equally good. I personally think that they should consider that the inventors of C-41, Kodak, doesn't condone such processing, and that therefore the burden of the proof ought to be on the others. But if they want to try it themselves, well ... let them have at it.
My background includes years as the QC manager in a large studio chain lab. Over the years, I was involved in perhaps ten or so trade trials of new films and papers for pro portrait use. We did our own intensive testing before considering usage in our chain, but the trade trials would include a handful of tech reps as well as film/paper engineers from the manufacturers, including Kodak, Fuji, and Konica. They would all have packages of exposed materials to be processed by us, to see how they behaved in thoroughly-seasoned processes. And they would want to take back some of our own test prints for eval. (By the way, we always stayed with the lowest speed Kodak pro portrait/wedding films, from CPS up to Portra.)
In our testing, we used a variety of models, with different complexions and hair colors, over a wide range of camera exposures. We also included color charts and some clothing/ fabric samples (we could put the actual clothing/fabrics in the color booth next to actual prints to see how close they agree). Our main visual criteria was for "good" skin tone reproduction across all complexions, without significant color crossover (from highlights into shadow areas). But no major color errors were allowed either. I think that many of the people on this forum would be astounded at how good the color reproduction was, or at least, could be.
One thing we did NOT specifically test for was out-of-spec processing; we had no need to know about such behavior. But we DID study, sensitometricly, what various things did in the film process (this knowledge is useful in "process control," in knowing how to troubleshoot).
Anyway, from this background, I'm very skeptical that "optimal" color reproduction will come from an out-of-spec film process. And I even doubt that a "normal person" can digitally fix a scan to do so, at least unambiguously. Sure, with a lot of digital manipulation one can get something good, provided that they know what it should look like. By if, for example, someone gives you some (out-of-spec process) film of strangers, with clothing you have never seen, could you fix up the files to get really good color reproduction? I'm really doubtful.
But I'm willing to be proven wrong.
Ps, I think a great deal of the give-and-take on these issues is a matter of how finicky, or perhaps sophisticated, people are about color reproduction. If one has never seen better, it's hard to appreciate how good something really is.