David A. Goldfarb said:The only additional thing that might be interesting, if it could be done successfully for presentation on the web, would be some illustrations from negatives and/or prints showing the effects of different pyro formulas, maybe with a standard developer or two like D-76 or HC-110 in there for comparison. I realize that there are resources like this out there in back issues of _View Camera_ and such, but it seems like this would fit naturally here.
Francesco said:Well done Sandy.
1. In this article you recommed a presoak in distilled water of 5 min. in BTZS tubes. In another you recommended 2 to 3 mins. Any real difference? (BTW, I place the distilled water in the tube caps and then shake it well for about 2 or 3 mins).
2. You recommed the use of a stop bath in the article. How long time should the film stay in the bath? You have also stated elsewhere that 1 minute in water was good enough if the fixer used is TF-4. Is this still the case? (By the way, I put the stop bath in extra BTZS tube caps and agitate slightly for about 30 seconds before I let the film lie in plain water for 1 minute. What do you think?).
jbrodkey said:However Sandy says you should mix the stock solutions under a hood or outside.
I live in an apartment house - no hood and hard to work outside. Photographer's Formulary
only supplies the powder although they do provide the stock solutions for several other Pyro developers. Why don't they supply Pyrocat in liquid form. Is there some reason for only supplying the powder?
john_s said:What a great article. It's time for me to mix some up and try it. One part of the mixing instructions I was not sure of, mixing part B. When you say that the "The total amount of solution will be slightly in excess of 1300ml" does that mean that the instructions for part B actually make 1300mL?
In other words, if I want to make 1000mL of part B should I use 769g of potassium carbonate?
Most formulas end with "water to make 1000mL"
Thank you for alerting me to this matter.
This part of the article is confusing and will I will see that it is changed as soon as possible. With the Stock Solution of Pyrocat-HD we should start with 1000ml of water and slowly add to the water 1000g of potassium carbonate. This will make a total amount of Stock B solution of approximately 1300ml. Previously published formulas made this step clearer but I can see that there could be some confusion with the directions as provided in the article.
jdef said:"Hi Sandy. I've found one point a little confusing. In your introduction, under advantages of pyro developers in point #3 you state " 3. When printing with variable contrast papers, pyro stain, which is always proportional to silver density, functions as a continuous variable color mask that reduces printing contrast, particularly in the high values. This allows shadow and mid-tones to be printed without compressing or blocking the highlights, reducing time spent burning and dodging. ", which suggests to me that reducing contrast in the high values is a good thing. Later, under Is Pyrocat Better Than Other Developers, you state "9. When printing with silver gelatin variable contrast papers Pyrocat-HD renders upper middle tones and highlights with more contrast than pyrogallol-based developers. ", which suggests that a reduction in contrast in the high values is a bad thing."
The fact that pyrogallol based developers reduce contrast in the highlights and that Pyrocat-HD renders these highlights with more contrast is neither a good thing nor a bad thing -- these are characteristics of the developers. Some subjects would benefit from the highlight compression, others would not.
"I've read reports by others that Pyrocat gives LESS speed than ABC, but you claim it gives more. Since you're the obvious authority in the use of this developer, I'm inclined to take your word, I just want to be sure that I'm understanding the information correctly."
I know for a fact that Pyrocat-HD gives more effective film speed that ABC Pyro. For that matter both PMK and Rollo Pyro do as well. I saw one report on the AZO formum by someone who said that he got more speed with ABC Pyro. But it was obvious from his description of results that the comparison tests were not develoed to the same CI, and it is pointless to compare effective film speed from different developers unless the films are developed to the same CI. Also, very few people have the equipment to really test effective film speed accurately. My exposures are made with a light integrator that guarantees accuracy to 1/100 of a second, and any comparsion development that I do has careful temperature control.
"You say that Pyrocat is an excellent choice for dual purpose negatives, silver and alt., but if I'm understanding your information, it is really an excellent choice for any purpose, i.e contact/enlarging small format/large format, tray/rotary etc. Is there any scenario in which another developer would be a better choice?"
OK, in what conditions would another developer give better results?
1. For 35mm work with some films you might want a tighter grain patterns than you get with Pyrocat-HD.
2. For scenes with a lot of very high tonal values the compression you get with PMK or Rollo Pyro might work better.
3. If you are after strange curves there are developers out there that will give interesting non-linear curves, unlike the nice linear, straight curves you get with Pyrocat-HD.
4. I would not use Pyrocat-HD for developing color emulsions.
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