Apples to apples comparisons

[N Dhananjay]

I must confess I was quite under-whelmed by the article as well. I noticed many of the same things mentioned above. In addition, I'm afraid I consider the article methodologically unsound.

A comparison of two developers is a complicated thing to do, because as Jay pointed out, there are so many dimensions to compare them on. To make menaingful comparisons, you typically want to control everything else except the dimensions of interest in a particular test. For example, if you want to test the film speed yielded by two developers, you have to develop them to the same CI etc. What this means is that a comprehensive comparison of two developers requires multiple tests across a variety of fronts. A really rigorous comparison would involve multiple measurements to make sure small differences are significant and not just due to random error, but with the reseach labs at Kodak gutted, I doubt anyone is going to have the patience/money to do that. At the least, one would require some level of experimental control. That would give us a theoretical understanding of the differences between the two developers.

Unfortunately, not everyone is comfortable with interpreting theoretical results and translating them into practical situations. That means some folks prefer to make pictures with the two developers and evaluate the results. Whether those results can show up in magazine reproductions is most unlikley. The biggest problem with this approach is the fact that there are interactions with subject matter. That is, one developer might naturally do much better with certain subjects than another and if that is the subject you shoot, you have skewed the results of your tests right off the bat, which is why I personally think this is methodologically not sound. It is absolutely fine if it is one individual trying to choose a developer to work with because s/he is interested in choosing a developer for his/her subjects. That is, the conclusions s/he draws are indeed constrained to the subjects shot. But in this case, there are generalizations being made that cannot and should not be made. Having used both developers a fair bit, I am highly dubious whether there are substantial differences between PMK and Pyrocat on the reported dimensions.

Cheers, DJ

[neil poulsen]

I don't know too much about pyro, having never tried it. But statisticially, this problem fleshes out fairly simply. For discussion, let's say that we have three responses, three different characteristics that we want to evaluate.

Contrast

Brightness

Edge Effect

In addition, we have two developers, Pyrocat HD and PMK, and we would like to evaluate the effect that these developers can have on the each of the above responses. We will need to determine a method to measure each of the responses, and likely, these methods will be different. One can't measure Contrast in the same way that they would measure Brightness.

So, we conduct and report the results of three separate experiments to determine how these developers affect each of the responses. (An experiment to compare Contrasts, a second to compare Brightnesses, and a third to compare Edge Effects.) This may sound simplistic, but I think that readers interested in pyro would like to know this information. They would find it useful. As DJ points out, there are subtleties, but the overall structure is straight forward.

The trick in all this is in addressing the question, "Which developer yields the most effective print?" This is indeed a trick, because this evaluation requires assessing all three responses at the same time, in the same set of prints. As to the method for making this comparison, one might photograph a given scene with the same brand of film, but developed in each developer. Then, perhaps the same printer would print the two resulting negatives the best way that he/she could, using the same print developer and paper. The printer should not know the source of each negative. A panel of viewers could evaluate the final prints (not knowing which is which developer), and these prints and the panel's comments could be included in the article for the reader to digest.

Of course, there are some problems encountered in the preceding paragraph, as there will always be. There's variability in how the printer would print each negative. Another problem is that perhaps one developer would favor cloud scenes during the day (e.g. John Wimberly), whereas another developer might favor night photography. So, pick whatever approach seems best. The important thing is that these problems should be pointed out in the article. If the reader knows the circumstances of each comparison, how it was done, the weaknesses, etc., they can then draw their own conclusions. One could do a study for both cloud scenes and night scenes, but if the article goes on endlessly, it loses its value. At the very least, the reader knows that each developer can yield good results under some circumstances. Or, perhaps the comparisons done might show that one of the developers is indeed inferior?

I think that including final prints in some context is worthwhile. After all, it's the final print that really counts. How final prints are affected will be a question in the readers' minds. As a statistician, I'm inspired by the work of Richard Henry in his book "Controls In Black and White Photography." He was a research chemist who applied his research methods to better understand B&W photography. He would frequently include final prints in his evaluations and have them evaluated by a panel of independent viewers. We may find no substantial differences, but that in itself advances our understanding.

[Jay DeFehr]

DJ, you make a lot of sense, as usual. I doubt wether the differences in developers of the same class are substantial enough to be important in practice. I am interested in the kinds of measurable differences noted above as a means to fine tune developer formulae, but my main criteria for developers of a common class are keeping properties and economy. If I can make up a concentrated solution that will develop hundreds of rolls of film for a few dollars, and that will last indefinitely on the shelf, I can learn the intricacies of that developer without the variations introduced in the making up process. It seems that a lot of the debate is centered around the championing of one formula over another, rather than personal use. I will try to make the kind of comparison that I noted in my previous post between the two developers that I'm currently working with, for my own personal information, but I will happily share whatever information I glean with anyone who is interested.

[sanking]

DJ makes many good points. Most especially as regards the importance of developing comparison negatives to the same CI, and to the importance of subject matter.

There are several areas of particular interest in film testing: apparent sharpness, appearance of grain, and effective emulsion speed. With staining developers you also have the question of how the color of the stain interacts with the sensitivity of a particular paper.

I have always been interested in comparing different films and developers and over the years have done quite a bit of testing. And since I don’t like to waste my time with meaningless comparisons I try to use sound methodology, which includes the use of sensitometry in the initial stages to assure that comparison negatives, whether for film or developer testing, are always developed to the same contrast, or CI. This is very important because the CI to which a negative is developed affects not only effective film speed but also sharpness and the appearance of grain. Even a very small difference in CI could potentially result in a big difference in all three of the primary evaluation areas.

Some might assume that it would be a fairly easy matter to determine the CI and EFS of a particular film developed in PMK and Pyrocat –HD but I can tell you for a fact that it is really quite complicated. My own comparisons are made in two steps. First, I use BTZS type testing (see Phil Davis’ Beyond the Zone System) and plot comparison curves from transmission step wedge. This data, however, which is based on densitometer readings, is not definitive because of the complication of the stain. So in a second stage I refine the CI and EFS values by matching PMK and Pyrocat-HD step wedge densities. And you need separate tests for indoor and outdoor lighting because films have a different response to different color light.

The next step if fairly routine. You make two negatives of the same scene, using the EFS indicated by your tests, and then develop the negatives for the time indicated by the tests. You should now have two negatives with identical printing density in the shadows and highlights.

Next, you make a print, basing exposure on first maximum black in the shadows. Now you can compare the results and make some meaningful comments. There will be some differences in the rendition of tonal vlaues between prints made with PMK and Pyrocat-HD due to the different color of the stain. The difference will be very small with graded silver papers, but could be significant with VC papers. With regard to sharpness we are now in the realm of the subjective because different observers might well come to different conclusions. For this reason better to have several people comparing results rather than just one. The problem with one observation is that he/she may have an existing bias and see what is already in his/her mind.

If you print with AZO or one of the alternative processes you would need to run new tests.

Over the past several weeks I have been thinking about a methodology that would provide a meaningful comparison of a couple of pyro staining developers with non-staining developers, limiting the comparison to one film but several different kinds of lighting conditions. As I envision the tests at this time there would be three parts.

1. I would determine the CI and EFS for the developers tests and make and develop the test negatives.

2. The negatives would be given to a master silver printer who would be asked to make the best print possible from each of the negatives, but using no dodging or burning.

3. The silver printer would then send the prints to three other persons, all with an established reputation, for visual evaluation.

This project would take a lot of work but it is something that I might be able to use in a book project I am currently involved in so it might be worth the trouble for me.

Meanwhile, the credibility of any evaluation of films and developers will be determined by interested parties based on the methodology utilized and reputation of the person making the tests or reporting the results. That said, my own evaluation of pyro staining developers in terms of the three areas of particular interest are as follows.

Sharpness – When the negatives are developed to the same CI there is no difference in sharpness between PMK, Pyrocat-HD and WD2D. I am convinced that any independent and objective comparison made by disinterested parties will come to the same conclusion.

Grain – There is virtually no difference in the appearance of grain between these three developers in prints up to 20X24” size from 4X5 negatives. Over this size Pyrocat-HD appears to have a slight advantage.

Effective Film Speed – No contest. Pyrocat-HD provides slightly more emulsion speed than either PMK or WD2D. I have been conducting carefully controlled testing of these developers for several years and in my mind there is no doubt about this fact. Steve Simmons appears to have reached another conclusion in his comparison of PMK and Pyrocat-HD, as did Jorge in the article in which he compared PMK, Pyrocat-HD and WD2D. But I stand by my conclusion, with full confidence in the methodology of my testing procedures, and in the knowledge that it is based not on one or two or even three observations, but on dozens and dozens.

[John D Gerndt]

So many people making so much sense!

I am glad to hear that you have a book project Sandy King. You seem like a scientist with an artist’s heart. Have you ever noted how many photographers started out in engineering?

Jay De Fehr has made a keen point as developers do belong in classes (show me the curves!) and one does need to work with each developer for some time to get a feel for what they do.

Now if only I had a large bunch of data to make an intelligent choice with…

Jay De Fehr makes a second keen point about economy. From what I can gather Pyrocat HD and good ‘ol HC-110 are the best in this regard. If Jay De Fehr has something cooking that is even better I might just swing that way but if I respect his first point I must consider staying with what I know…there is the rub!

My thanks to all who share their data; I have learned more about photography and sensitometry this year, through this forum, than I did in the last ten years of shooting in the dark!

Cheers,

[sanking]

John,

Actually I am one of those humanistic types with a Ph.D. in language and literature studies but there is a lingering suspicion in the back of my mind that I should have been engineer instead. But at least my career has given me the opportunity to pursue my interests, which include not only image making but the history and aesthetics of photography as well as image making.

As for the book, those who participate in the AZO forum are already aware of the fact that the book is a joint project with Michael Smith and we will each be contributing to the book in the areas of our greatest interest. In my case that is alternative printing processes, exposing and developing film, use of pyro developers, and digital negatives for alternative and silver processes. I am very pleased with the collaboration because Michael is in my opinion one of the most outstanding photographers of our time working in what I call the pure or straight photography tradition of Weston.

Since both Michael and I are proponents of pyro staining developers a study of the type I suggested in a previous message could be an interesting addition to the book. But if I do indeed do such a study the objective will not to be to prove that one developer is better than another, but to discover and report the differences and how we can take advantage of them. And the methodology will be as sound as I can devise, and the reasons for any conclusions transparent and open to criticism.

[Brian Ellis]

Chris - The way you suggest doing it is, IIRC, exactly the way Phil Davis does it in his BTZS workshops - i.e. he matches the darkest shadow and the brightest highlight from print to print then looks at everything in between to compare negatives and developers (or something very close to that, it's been about 8 years since I attended his workshops). Of course you need a densitometer to do this with complete accuracy and once you say "densitometer" to some magazine editors you hear things like "I'm a photographer, not a lab worker," "some people spend their time running tests, I prefer to spend my time making photographs," etc. etc.

[Tom Duffy]

You guys are making this much too complicated. Pyrocat works flawlessly in a JOBO, PMK doesn't.

[Kirk Keyes]

Tom - why do you say PMK doesn't work flawlessly in a Jobo? I find it works quite well.

[Tom Duffy]

Kirk, With 5x7 and 8x10 sheet film in a expert drum, areas of the neg such as clear blue sky often ended up streaked with uneven development or staining. I found I was ruining more negs with PMK than I was helping. I never, repeat, never had a similar problem with Pryocat. As an added advantage, Pyrocat has much less general stain and the negs print in half the time. take care, Tom