As usual,

@Stephen Benskin and

@Bill Burk pointed out some really interesting ideas related to describing film performance. This time, I went back to Way Beyond Monochrome (Lambrecht and Woodhouse, Fountain Press, 2003) and re-read the relevant chapters. I decided to take a deeper dive and see if I can offer analysis and visualization tools for their model. I would imagine a lot of photographers have read the book and tried to implement the model into their own workflows. The book contains templates that can be printed out and used to analyze the data. That analysis is done mostly visually, with some simple calculations needed. This tool, however, offers a computer-aided analysis. The idea is to just enter the data into a spreadsheet, set a few preferences, and run the program.

I am asking for your feedback. This is just a first attempt at creating these visualization tools. My goal is to create a tool that is as simple as possible, both to use and to interpret, but without leaving important bits out. Bear in mind, this model, just like most other existing models, is not perfect, but I think it can be implemented successfully.

The gist of the WBW model is on p. 128. The idea is that there's a simple, linear relationship between "subject brightness range" and the Zone System (represented by the N-numbers), where seven stops is considered normal, and each stop (or EV) of brightness range in either direction, corresponds to a single step along the N-numbers continuum.

The next important relationship is between the average gradient (Ḡ) and the Zone System (N). It's important to point out that the authors consider a density range of 1.20 to be best suited for a contrast grade-2 paper in combination with a diffused light source. As

@Stephen Benskin pointed out, this is not as simple as it appears, but, for practical purposes, it can be assumed to be a reasonable approximation. For a condenser enlarger, a different value may be needed, and the tool needs to be able to accommodate that.

The analysis of the film exposure and development, in my opinion, can be summarized by four plots. I will be using my TMY-2 data for this as an example.

The first plot shows the relationship between the average gradient and development time. The curve represents the actual data, but the N-number labels are derived from the WBW model. Essentially, you can look up any combination of time and Ḡ and compare it to the Zone System (N). The blue line represents the normal development for an average gradient of 0.57. I decided to only include the range of N-2 to N+2 here, but I would leave it up to the user to decide on the range. In the book, this plot is on p. 138.

The next important view of the data in the WBM system is the relationship between development time and the Zone System (N). Here, we can compare the actual values (from our TMY-2 data) and their relationship to the WBW model. We can see that a "normal" development time in XTOL-R is a little under 9 minutes in a Jobo processor at 20C. The same, of course, can be read from the plot above, but that's just a different look at the same data, so to speak.

Next, the plot of relative log exposure and the average gradient. In the book (p. 139), they recommend to use it as a tool for estimating effective film speeds of the curve family. I think that presenting such data in a table might be more effective. I am still not sure how to go about this. This is a somewhat unusual plot because, often, we associate the average gradient with development time, rather than exposure, so it can be potentially misleading. There is another wrinkle here, namely, one needs to do an additional test to determine normal film speed, and then use this plot to estimate effective film speeds in relation to film speed obtained in that test. I guess I am making it sound more complicated than it is. In essence, a 0.1 change in log exposure equals 1/3 stop in film speed. The EI values at the bottom of the plot are rounded such that they should be easy to use with an exposure meter. One of the important conclusions is that the "normal" film speed, or EI, is around 320.

Finally, there's the plot of effective film speeds and the Zone System (N). This plot shows how "sensitivity decreases with development contraction." This plot is supposed to instruct the photographer regarding their exposure and development decisions in the field. Unlike the previous plots, this one does not include the actual TMY-2 data, but, instead, it shows the relationship between the N-numbers and film speed, derived from the actual data. Again, I am not sure how clear this distinction is. Please, let me know what you think.

I hope to put together an installment about testing paper, and then relating film and paper data to each other. More to come.