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  1. #21
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    I think the specific question you had was about VC paper and highlight control.

    There are two things going on - the first is tanning of the gelatin. This is common to all the pyro type developers, including pyrocat. The tanning action hardens the gelatin and helps prevent runaway, or infectious development in really hot highlight areas. This is one way that all pyro type developers are supposed to help 'tame' really bright highlights. Think of this contrast control as a 'global' effect that will affect the entire density range of the negative

    The second issue is the stain color. This is where pyrocat differs from PMK, ABC and Rollo. All except ABC use metaborate to create the high pH necessary to develop the film, and it will cause a yellow-green stain. In fact, I have proven accidentally that if you use metaborate and part A of pyrocat together, you will get a green stain, not to mention a bulletproof negative! This green stain ideally is proportional to the silver density, so the highlights are more green than the shadows. The green effectively filters the bluish high contrast light that affects the high contrast part of VC paper emulsion. So a green pyro proportionally stained negative will cause the highlights to print softer 'automagically' on VC paper. Think of this contrast control as 'local', since its effect is concentrated where the most stain occurs, i.e. the highlights.

    Pyrocat, on the other hand, has a brown stain color, and does not seem to cause the same highlight softening as the metaborate based developers and ABC. So, you get more highlight contrast with VC papers and pyrocat. But you still get the global highlight control of a tanning developer. So the statements are not necessarily contradictory, as I think Sandy is referring to two different attributes of the developers.

    Of course, I'm putting words in Sandy's mouth, so Sandy, call me down if I am full of it.

    Clay

  2. #22

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    [quote="jdef"]

    "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.

    Sandy

  3. #23

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    im looking for a source for the Potassium Carbonate mentioned in Sandy's formula..i cant see it on the list at artcraftchemicals but can see potassium bi-carbonate (anhydrous) at photographers formulary..is the bi-carbonate the same stuff in sandy's formula?

    -andrew

  4. #24

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    Potassium Carbonate is not in order with the rest of the Potassium compounds on Artcraft's site. Just keep scrolling down or search the page for it. It is near the bottom of the chemical compounds just before the Zonal Pro chemistry.
    Paul Hamann

  5. #25

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    I've posted this elsewhere, but felt I should do it here.

    Sandy's article is one of the best articles about the technical aspects of photography that I have ever read. For those interested in developing negatives with Pyro this is a must read.

  6. #26

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    Quote Originally Posted by john_s
    Ole says above"Think you could change the recipe to give 1000ml final solution? It would be a lot easier for those of us who put the finished solutions in 1000ml (or 100ml, in my case) bottles. "

    That's what I was driving at when I suggested 769g with water to make 1000mL, based on Sandy's figure of 1kg pot carbonate plus 1Litre water to make "approximately" 1.3Liter. If it's hard to get all of the pot carbonate to dissolve (sounds like a possibility) i'd be tempted to make up half strength part B and use 2x as much (as I do with PMK, since I found it impossible to get the full amount of metaborate to dissolve in the required amount of water)

    From my perspective there are advantages to expressing the formula for Stock Solution B as it presently is, and there are advantages to doing it the way you suggest. However, if I change the way the formula is expressed at this point in time I will get about 500 email messages over the next six months asking me to explain the discrepancy, and since I answer all my email you can see the problem. However, what you propose makes perfect sense and if it is more convenient for you to mix this way by all means do so.

    I don't know how to explain why some people have difficulty in getting 1000g of potassium carbonate to go into solution in 1000ml of water. But I think the secret is to add the carbonate to the water very slowly, with constant stirring. It never takes me more than a couple of minutes to get it all into solution when I add it this way.

  7. #27

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    Quote Originally Posted by Black Dog
    vvg article-excellent intro but covers plenty of ground as well. You mention using hypo clear btw-won't the sulfite in this remove some of the stain?


    No, I tested this. Negatives that are cleared with 1% sulfite show no decrease in the level of stain.

  8. #28

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    In your article you speak of streaking and pressure marks. To be clear, is this streaking increased or decreased film density? I assumed that since the cure is to load the film wet so that there "is a transfer of chemicals on the base of the film", that the streaks would be decreased density due to less developer action. Is that right?

  9. #29
    Ole
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    Quote Originally Posted by sanking
    I don't know how to explain why some people have difficulty in getting 1000g of potassium carbonate to go into solution in 1000ml of water. But I think the secret is to add the carbonate to the water very slowly, with constant stirring. It never takes me more than a couple of minutes to get it all into solution when I add it this way.
    My guess is that they take 1 kg potassium carbonate and try to make 1 liter finished solution, instead of combining 1 liter of water and one kilo potassium carbonate...

    It's no problem at all dissolving it - but then again I "cheat" and use a magnet stirrer!
    -- Ole Tjugen, Luddite Elitist
    Norway

  10. #30

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    Thank you for your article Sandy. I have been struggling to find an ideal developer for sheet film for a while. I use Fortepan 200 in 8x10 and have tried it in D-76, DK-50, HC-110, ABC pyro and Rodinal all producing good, but not great results for enlarging. I have tried PMK in 120 a few years ago and loved the sharpness but could not stand the muddy highlights it often produced with vc papers. Graded papers were fine but not readily available here in Australia anymore.

    Yesterday I decided to mix up some Pyrocat-HD and processed some test sheets of 8x10 Forte 200 rated at EI:100 for 16 minutes at 20 degrees. The results were fantastic. The rich brown stain noticably different from that of PMK. I enlarged a small section of the neg about the size of a 120 neg up to 8x8 inches. The sharpness and lack of visible grain is quite incredible. Highlight tones are silky smooth and luminous whilst the midtones are rich with excellent separation.

    It appears that I should be able to make enlargements from 8x10" negs up to 30x40 inches in size without a problem. This is exactly what I have been looking for.

    Thank you so much for the work& time you have put into researching & publicising your formula.

    Regards,

    Matthew Stanton

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