steve simmons said:
IMHO the best of the formulae is still the PMK developed by Gordon Hutchings in the early 1980s. The definitive work is called The Book of Pyro also by Hutchings. I have used this formula for 25 years and have never felt a reason to switch. If someone can prove to me there is a better pyro formula please do so.
When I first saw this message a few days ago I started to respond but did not have the time to give the issue the attention it deserves. First, let me state that Steves personal satisfaction with PMK based on 25 years of experience is not surprising. PMK is without question one of the best all around developing formulas available and I used it for almost ten years as my primary developer. But let me begin with two preliminary observations.
1. I know a photographer who has used D-23 for more than twenty-five years and would not consider changing to another developer. The fact that we are satisfied with our developer and dont feel a need to change is ample reason to not do so, but it does not mean that a given developer is better than another.
2. Steves statement that in his opinion the best of the formulae is still the PMK developed by Gordon Hutchings in the early 1980s suggests that he has actually compared the current crop of Pyro formulas. At least that is how I understand the issue because I personally would not say that one developer was better than another unless I had some experience with both of them. So, Steve, if you have actually made any objective comparisions of PMK with other Pyro developers please show your criteria, methodology and results.
It is my understanding that Steve plans to publish an article in View Camera at some time in the future comparing pyrogallol and pyrocatechin developers, perhaps directly comparing PMK and Pyrocat-HD. Let me state right here that since I have used and tested both of these developers extensively I already know what a well-designed comparison test of the PMK and Pyrocat-HD will find. And I am going to reveal some of that information here now. My criteria for comparison are, 1) sharpness and grain, 2) rendition of tonal values, and 3) versatility, and 4) suitability as dual-purpose negatives to print with both silver and Pt/Pd. Some of these criteria may not be important to many readers but they are all important in evaluating the two developers in terms of their overall versatility.
1. Sharpness and Grain.
First, lets start with the points of similarities between PMK and Pyrocat-HD. Both are semi-compensating high definition developers staining developers . When used at the recommended dilutions for silver printing (1:1:100 for Pyrocat-HD, 1:2:100 for PMK) they give negatives that are virtually identical in terms of sharpness and grain.
I tested sharpness and grain in two way. First, I made two identical exposures of an outdoor scene with a 4X5 camera, and after calculating time of development needed for an equivalent CI, developed one in PMK and another in Pyrocat-HD. Then I made 20X24 prints from the negatives.
Result: At 5X magnification there was no discernible difference in either sharpness or grain between the two prints.
So I tested again for higher magnification, using a Fuji 6X9 cm camera with a 90mm Fujinon EBC lens, obviously on a tripod. I made eight exposures on Tmax 100 120 roll film of the Edmund Scientific Company Resolving Power Chart, a reproduction of the USAF 1951 Test Pattern. I made exposures at f/5.6, f/8, f/11 and f/16, then repeated the sequence. In the darkroom I cut the 120 film into two equal lengths and developed one set in PMK and the other in Pyrocat-HD. I dried the negatives and them examined them at 40X magnification with a Bausch and Lomb stereoscopic microscope.
Result: The resolving power of the 90mm Fujinon EBC lens approached 100 lpm with both PMK and Pyrocat-HD negatives. Clearly the limitation to resolving power was in the optical system and/or film, not in developers.
Ditto for grain. Virtually no difference between the two negatives.
Conclusion. At a magnification size of 40X (that would equate to a print size of 90X 90 from a 6X6 cm negative) there is for all practical purposes no difference in sharpness or grain between PMK and Pyrocat-HD negatives.
Do we need to say anything more about sharpness and grain?
2) Rendition of tonal values.
When developed to the same CI, PMK and Pyrocat-HD give negatives that print the same on graded silver papers, which are sensitive to blue light. With VC papers there are issues. For a complete explanation of these issues see my article on staining developers at http://unblinkingeye.com/Articles/PCat/pcat.html
. But the bottom line is that PMK has more of an effective shoulder than Pyrocat-HD, the practical result of which is that in scenes of great contrast range PMK holds highlight detail better than Pyrocat-HD. But, with developers you dont get something for nothing, and the down side of the shoulder is that with VC papers PMK negatives print the upper mid-tones and highlights with less separation (= less contrast) than Pyrocat-HD negatives. If you don't believe me on this just check the literature because there have been many comments by PMK users about lack of separation or contrast in upper mid-tone separation in certain kinds of lighting.
Conclusion: The differences in shoulder are developer characteristics, not advantages or disadvantages. When printing with VC papers some scenes would print better with PMK while others would work better with Pyrocat-HD.
Based on my research and experience there is little question but that Pyrocat-HD is a more versatile developer than PMK. The main reason is that pyrocatechin is more stable in alkaline solutions than pyrogallol and it oxides much less rapidly. The practical consequence of this fact is that Pyrocat-HD works equally well in both tank, tray and rotary (Jobo, BTZS tubes) processing, and with all kinds of agitation, including minimal and semi-stand. This means that you can use Pyrocat-HD with minimal and semi-stand agitation to maximize adjacency effects and apparent sharpness. With PMK you can not use these types of agitation because the rapid oxidation of the developer requires frequent agitation to avoid uneven staining.
4) Suitability as dual purpose negative for silver printing and printing with Pt/Pd.
Again, see my article for a fuller explanation of why Pyrocat-HD negatives are more suitable than PMK negatives as dual purpose negatives for printing with both silver and Pt/Pd (and other alternative processes sensitive to UV radiation). This is due to the fact that Pyrocat-HD negatives have a much greater difference between the effective printing density for UV light processes and blue sensitive light processes than PMK. This results from the fact that a much higher percentage of the effective printing density of a Pyrocat-HD negative consists of brown stain, which functions as a much more effective filter to UV light than the green stain of PMK negatives.
Consider for example the following density reading of highlight and shadow values of PMK and Pyrocat-HD negatives, bearing in mind that the Blue readings are for silver printing with graded papers, UV for alternative processes.
-----Highlight Reading---Shadow Reading---- DR
Blue 1.67 -------------- .47 ------------ 1.20
UV --2.30 --------------.67 ------------1.63
------Highlight Reading---Shadow Reading---- DR
Blue 1.61 -------------- .45 ------------1.16
UV --1.80 ------------- .62 ------------1.18
Anyone who understand the practicalities of printing with both silver and Pt/Pd will immediately understand the reason why a Pyrocat-HD negative makes a better dual-purpose negative.
None of the above is in any way intended to convince Steve Simmons to switch to Pyrocat-HD from PMK. Persons who develop in trays and print exclusively with graded silver papers have nothing to gain in switching. For all other conditions there might be reason to reconsider.
Opinions are one thing. And not always the best things. Which is why I always say, spare me the opinions, just the facts please.