Tuning the Hybrid Film/Digital process
Part one - film calibration
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Introduction
Like every photographer who hasn't gone completely digital, I'm constantly re-evaluating that decision.
There are compelling reasons for me to stick with film capture - the ability of digital capture to handle extreme subject brightness ranges, the robustness of digital equipment out in the real world environment (e.g. rain, fog, and dew), and the relative lack of resolution on a par with a 4x5 sheet of film.
On the other hand, the smooth tonality of digital capture, along with the incredible ease of making lots of exposures and dealing with them digitally - it beckons. If I could buy a digital back that offered something to the resolution of a 4x5 sheet of film, I'd probably do it. But the prices remain above what I can justify, so I remain firmly in the hybrid film/digital camp, and I'll stay there until the prices drop.
In the meantime, I'm left wanting to optimize the hybrid film/digital process, and get the best results I can. Is there more performance that can be wrung out of film if we abandon the notion that we're going to print it on gelatin silver paper, and tune everything for scanning?
So I've decided to tune that process - pick the best film for scanning, the best developer for scanning, develop the film to the optimum densities for scanning. Before I can optimize the process, though, I have to first be able to control it. That means I need to be able to make exposures on several different films, and develop the negatives in several different developers, and get negatives with the same contrast. It's important to change only one variable at a time - and to do that, you need to control all the others.
The Films
Most of the time, I use the film I consider my old reliable friend - TMX, aka TMax-100 or what Kodak is now calling Tmax 100 Professional (or some similar variation).
I like it, primarily because I've used it for so long that its various shortcomings have become part of my thinking. I'm used to the tonal rendition it offers, and I like the fine grain and sharpness. And, joy of joys, it can be bought in Readyloads, which I consider a great convenience.
Tmax-400 is another favorite of mine. I have a bunch in the freezer, so I'll do the work for this film as well. I'm interested to see how well it fares when scanned compared to TMX and Acros.
Finally, another candidate is Fuji Acros 100 - similar to TMX. I compared TMX and Acros a while back, when I was silver printing. Now that I'm scanning the film instead of doing optical enlarging, it's time for a rematch. Alas, Acros is difficult to find in loose sheets (easy in Quickloads at $2.50 a sheet) which makes it expensive to do extensive testing with it. On top of that, Acros has substantially shorter development times than TMX and TMY, so that it's hard to combine development runs. My plan is to do the testing with TMX and TMY, then go back and do testing with Acros where it seems to make sense. That way, I don't waste time and money testing combinations that are likely to be losers.
There are other films of interest - Ilford's Delta 100 and Delta 400, and FP-4+ and HP-5+. But for now, I'm ignoring them. I think I'll have my hands full and learn plenty from doing the three films. Later, when I'm done, I'll go back and reconsider other films. Having mapped out the process with these three, it should be easy to add others to the set later. My experience tells me that I learn a lot from the first time through a process, so it's wise to go through it once with a limited set and then add more later, after I've learned those lessons (or, as my daughter so neatly puts it, "Oh, NO! Another God-damn learning experience!!!").
The Developers
Using the same reasoning, I'm limiting the set of developers. I've already done a rough and ready comparison of Tmax-RS (diluted 1+9) and XTOL for scanning, and the Tmax-RS finished a definite last. So Tmax-RS, my developer of choice for many years, is not on the list.Xtol, though, produces negatives which scan nicely. My plans are to evaluate XTOL at four different dilutions (1+0, 1+1, 1+2, 1+3). Why try them all? Because I'm wondering what difference I'll see in sharpness, grain, and noise when scanning as the dilution is changed. Is there an optimum dilution? Enquiring minds demand to know.I've learned a few things about scanning negatives by going back and scanning older 4x5 negatives. One negative I have scans particularly well - I've made a beautiful print that's about 40" x 50" from it, and it looks awesome. And it turns out that negative was developed in the old standby - D-76. My notes are fuzzy and inconsistent on the dilution - it might have been straight, or it might have been 1+1. So I'll evaluate both.Finally, I keep hearing about the wonderful attributes of a much maligned developer - Microdol-X. In the small format world, it's despised for it's softness and loss of film speed. In the hybrid world, I'm finding a much greater need for smoothness than sharpness, and a loss of film speed doesn't bother me at all. So Microdol-X, both straight (1+0) and diluted (1+3) is in the mix as well.Are there other developers that would be interesting to evaluate? Sure. A real evaluation of Tmax-RS would be a good plan. I'd love to do pyro based developers, particularly the pyrocatechol based ones. And D-23 is on the list as well. But again, better to proceed with a reasonable first set, work out the methodology, and then expand later.The Calibration Process
In Ansel Adam's epic tome, The Negative, he outlines a film testing procedure that suggests that we might find the normal development times for a film/developer combo by exposing three sheets of film, processing them, measuring the zone I, zone V, and zone VIII densities, and iteratively adjusting development times until we get the results we want - film calibration by successive approximation, if you will.
Adams is often referred to as St. Ansel, and if he actually used this process to do film testing, then he surely had the patience of a saint. I, however, do not.
Instead, I will use the following changes - first, instead of exposing three sheets of film using my camera (and thus capturing things like shutter variation, meter variation) I'll make the exposures on one sheet of film, under my enlarger, using a Stouffer 31 step .1 density step wedge.
And, instead of finding the development times by successive approximation, I'll make three runs at carefully chosen development times, and I'll use the measurements from those three sheets of film to build a curve that describes the variation in Zone VIII density as a function of development time. Given that curve, I'll then use it to calculate the times to give the right Zone VIII densities for N-2, N-1, N, N+1, N+2 development.
Furthermore, if I'm very clever (and moderately lucky) those three development times can be chosen so that they'll do the trick for all the films I'm calibrating - so I can combine development runs on the Jobo and calibrate all three films in parallel. (Note: although this was my plan at the start, it turned out the times for Acros were too different from those for TMX and TMY, so I couldn't combine runs)
What looked like hundreds of development runs on the old Jobo has now been reduced to three runs per developer/dilution. For the eight developers and dilutions I want to test, that works out to 24 Jobo runs. At two runs per hour, that works out to 12 hours of standing in front of the Jobo, listening to it whirr along while I wait for the timer to beep. Clearly the first step is a visit to the library to lay in a supply of mystery novels!
How It's Done
The process I've described is roughly how I got the development times for TMX and Acros in Tmax-RS that I've published in this article.
Here's how it works: I did a three development runs with TMX, in Tmax-RS diluted 1+9, at 75F. The development times were 5 minutes, 10 minutes, and 15 minutes.
Measure the density difference between the step that represented Zone I and the step that represented Zone VIII (21 steps on my step wedge, one third of a stop in exposure per step), I got the following results
Time (minutes) Net Zone VIII density 5 1.0 10 1.54 15 1.93
Now, I can make a graph of these data:
There are two interesting things to notice. First, the three points make a nice smooth curve. Second, they don't quite make a line - but they're close.
It turns out that I can fit a simple curve (a second order polynomial, in fact) to the points, and get an equation for that curve. That equation gives me a way to predict what Zone VIII density I'll get for any development time reasonably close to those three test data points. That is, if I want to know what Zone VIII density I'll get if I develop TMX in Tmax-RS for 12 minutes, I can get it. If I want to know what density I'll get for, say, one minute, or 100 minutes, I probably can't. 1 minute and 100 minutes are extrapolations instead of interpolations, and they're too far away from the test data (too much of an extrapolation) for me to be confident. But for anything between 5 minutes and 15 minutes, or even between, say, 3 minutes and 20 minutes, I'm pretty golden.
Now, all I need is a table of the desired Zone VIII densities for N development, for N-1, N-2, N+1, N+2, and I can happily predict away.
That's it. I take that curve, calculate the development times for N-2 through N+2 development, and I'm done. Three sheets of film, three development runs, some measurements, and I have everything from N-2 to N+2, in the bag.
Thinking is way easier than working.
The Details
Ok, when I develop film, I do it in my Jobo CPP-2. The film goes into Jobo 3010 Master film drums.
The rest of the process is pretty standard:
- Prewet - I use no prewet. My testing shows no difference between films developed with a prewet in the Jobo, and films developed without except for changes in development time. Since I calibrate my own development times, I save time and don't use a prewet stage.
- The specific development time and temperature varies depending on film and developer, of course. It's listed with each combo, below in the results section.
- Stop Bath: I use a 30 second stop bath. The stop bath is 1.25% acetic acid.
- Fixer: I use a 5 minute fix in Kodak Rapid Fixer, diluted as per the instructions except that I don't use the part B (Hardener) for 4x5 film.
- Clearing agent: I use a 2 minute clearing agent bath. In particular, I use Heico Permawash, diluted according to instructions.
- Wash: I use an 8 minute wash. For normal film development, I do the wash in the Jobo, changing the wash water every 30 seconds. For film testing, to save time I wash the film in a tray with running water, which frees up the Jobo for the next development run.
D-76 1+0 @ 68F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 3.9 -0.5 N-1 4.5 -0.3 N 5.3 0.0 N+1 6.4 0.4 N+2 8.1 0.9
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 4.6 -0.3 N-1 5.1 -0.2 N 5.8 0.0 N+1 7.0 0.3 N+2 9.3 .8 D-76 1+1 @ 68F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 5.9 -0.6 N-1 6.7 -0.3 N 7.8 0 N+1 9.2 0.5 N+2 11.4 1.2
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 6.9 -0.5 N-1 7.7 -0.3 N 8.8 0 N+1 10.2 0.3 N+2 12.1 0.8
Microdol-X 1+0 @ 75F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 5.3 -0.4 N-1 5.7 -0.2 N 6.1 0.0 N+1 6.8 0.2 N+2 7.8 0.6
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 5.2 -0.5 N-1 5.7 -0.3 N 6.3 0.0 N+1 7.1 .3 N+2 8.4 0.6
Microdol-X 1+3 @ 75F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 7.3 -1.0 N-1 9.2 -0.5 N 10.8 0.0 N+1 12.4 +0.4 N+2 13.3 +0.5
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 9.1 -0.5 N-1 10.4 -0.3 N 11.9 0.0 N+1 13.8 0.3 N+2 16.4 0.8 XTOL 1+0 @ 68F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 4.8 -0.3 N-1 5.4 -0.2 N 6.2 0.0 N+1 7.2 0.2 N+2 8.5 0.3
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 5.1 0 N-1 5.5 0 N 6 0 N+1 6.9 +0.1 N+2 8.5 +0.3 XTOL 1+1 @ 75F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 5.6 -0.9 N-1 6.2 -0.4 N 6.8 0.0 N+1 7.7 0.4 N+2 8.7 0.5
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 4.7 -0.5 N-1 5.1 -0.3 N 5.7 0.0 N+1 6.5 0.3 N+2 7.8 0.4 XTOL 1+2 @ 75F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 7.6 -0.2 N-1 7.9 -0.1 N 8.3 0.0 N+1 9.0 0.2 N+2 10.3 0.5
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 8.3 -1.2 N-1 9.0 -0.6 N 10 0.0 N+1 11.2 0.4 N+2 12.9 0.8 XTOL 1+3 @ 75F
Tmax-100
Development Time (minutes) Speed adjust (stops) N-2 11.0 -1.1 N-1 11.9 -0.5 N 13.1 0.0 N+1 14.5 0.4 N+2 16.5 0.7
Tmax-400
Development Time (minutes) Speed adjust (stops) N-2 8.8 -0.2 N-1 9.4 -0.1 N 10.1 0.0 N+1 11.2 0.1 N+2 12.9 0.3
