film categories: which are "retro" and which are not?

Pixophrenic said:

Thank you, PE. Not sure why you chose Tri-X to support D-76. That's a lot of data, and often difficult to read curves. Contrast index curves for D-76, oddly, are much shorter than shown for newer developers, they do not go past 10-minute point. However, the suggested times for 3-stop push with D-76 go very much past 10 minutes. T-Max RS, D-76 and Xtol are the developers recommended for 3-stop push, then why D-76 contrast index data are omitted?

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To answer your question, ask Kodak.

As for your comments on push processing, I must remind you that a push process usually only increases contrast, not true speed. If true speed were to be increased, then it would be done at constant contrast. And BTW, that is one of the ways to read those curves. Pick a constant contrast for all developers and start from there.

I picked Tri X because that is what I found handy on the EK web site. Most have been removed by now. Which one would you have picked?

PE

Photo Engineer said:

To answer your question, ask Kodak.

As for your comments on push processing, I must remind you that a push process usually only increases contrast, not true speed. If true speed were to be increased, then it would be done at constant contrast. And BTW, that is one of the ways to read those curves. Pick a constant contrast for all developers and start from there.

I picked Tri X because that is what I found handy on the EK web site. Most have been removed by now. Which one would you have picked?

PE

Click to expand...

It would be more interesting, PE, if you started with T-Max films, as their info papers can be had just as easily. It gets more interesting in there than with Tri-X. Contrast index curves on page 16 for T-Max 100 show that for small tank at 20 C, with stock D-76 (and XTOL) only 2 minutes (6-8 min) of development separate contrast index of 0.55 to 0.8. If you are after 0.65, you have to be very precise timing your process. Develop for 10 minutes, and technically it is not a pictorial film anymore. With 1:1 dilutions both developers get easier to handle, usable contrast raise is between 9 and 13 minutes. However, 6 minutes separate the same span of contrast index for stock T-Max developer. Obviously the chemistry was advanced with this developer, beside it being sold as liquid. IMO, this behavior of T-grain films more than anything explains the popularity of dilute developers with them. It also means that if the film is sent to a lab using stock D-76, using median devt time as you told me earlier, my chances to get back a film without one stop push, uncalled for, are slim, but they get much better if the lab happens to use T-Max or T-Max RS developer. It is interesting that for rotary tube and tray, D-76 is omitted from T-Max data altogether, available data only for XTOL and XTOL 1:1 show that they behave similarly (rapid rise of contrast), but at a different starting time point. There is, of course, a disclaimer that all of the above is only representative of a sample tested, and does not necessarily apply to the roll you purchased. I have not found a lab that uses XTOL, but from the above it follows that if I were interested in a T-Max film developed in a lab, I'd rather give it away to one using T-Max developer. Sounds almost trivial.

There is probably an error in that data. The sensitometric curves show straight lines with good contrast at the two lower development times in both developers in a small tank. The contrast charts do not entirely agree suggesting the data is mislabeled somehow.

It does illustrate blended emulsions (the bumps in the curves) and the fact that these films grow in contrast rather rapidly depending on developers.

Please look at the two pages again. Something seems wrong.

PE

Ron, the Tmax PDF just indicates that the contrast of Tmax 100 will build up quickly during development, faster than with Tri-X

Here's the comparative graphs, I've adjusted the Tri-x scale to be a better comparison.



Something we've all now since John Sexton's articles when he was testing Tmax for Kodak prior to its release

Ian

Apologies there's an error in the above image as I mistakenly thought both started at 0 mins/


Tmax100 is this small chart on the right.

I think the OP is reading too much again into why people use developers like D76/Xtol at 1+1 or even 1+2 or 1+3. It has nothing to do with the slightly steeper contrast rise with development with Tmax films, it's more that people started using rotary processors and a 1+1 dilution is ideal under these circumstances.

Contrast with Tmax films and even Foma which are far more finicky is easily controlled without resorting to dilution, people use dilution for entirely different reasons, development times and temperatures should be kept tight anyway regardless of the fil, developer or dilution.

Ian

I am only looking at the T-Max data, both development times and contrast rate of change. There is a mismatch that does not make sense. The rate of D76 is higher in contrast change than appears in the H&D curves. I'm still studying it, but it looks strange to me.

PE