Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,953   Posts: 1,522,760   Online: 985
      
Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 25
  1. #11
    juan's Avatar
    Join Date
    May 2003
    Location
    St. Simons Island, Georgia
    Shooter
    Multi Format
    Posts
    1,637
    Images
    4
    OK, here's the potentially stupid question of the day. What about Pyrocat-HD as a two-bath developer? Why? Because with the SBR range where I photograph and the temperature at which I have to develop, I continue to have trouble with negatives with too much contrast for even Grade 2 Azo.
    juan

  2. #12

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    No, what it means is that sulfite and a superadditive agent will be in competition. With phenidone, you don't have this problem and this is one of the reasons why PQ is more superadditive than MQ.

  3. #13
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    Quote Originally Posted by jdef
    Pat,

    I would like to make the comparison you suggest, but I'm not sure I know exactly how to do it. If I want to duplicate the two bath developer as a single bath, don't I need to know how much of the first solution is being carried over into the second? Should I expect to see similar results by simply combining the two baths into one? Can you suggest a formula for a single bath that would approximate the quantities and ratios present in the two-bath development? Since you're here, I have some questions I thought you might be able to answer. I read your article on the synergism of phendione and ascorbic acid, and understand the role of excess ascorbic acid in the developer solution, but two-bath developers represent a special circumstance, and I'm not sure how the ratio works. How much metol do you think is being carried over into the second bath by a roll of film, assuming 5g/liter of metol in the first bath? I realize that an excess of ascorbic acid in the second bath is necessary, but I don't want to waste it unnecessarily. I made up a liter of your Stock A without the metol, which contains 8g of ascorbic acid in a buffered borax/NaoH alkali. The omitted metol is .8g, or 1/10 the asorbic acid, which I replaced with 5g of metol,25g of sulfite, and 3g of 50% gluconic acid in a liter of water for the first bath. The first bath is stored in an open pitcher, and the second in a stoppered flask. This combo is going on its third day, with no signs of exhaustion/oxidation, which seems to exceed the requirements for a single-session developer. It seems to me that two-bath development depends on excess, which makes it friendly to teaspoon measurement, and so practical in most darkrooms, but I don't need to tell you that.


    Jay
    Now Jay, all I meant to do was to develop a test strip with the 2-bath and then mix A and B together and find a developing time that will get you the same contrast for printing. You may have to dilute it some. The object is to find if you are getting better negatives from your 2-bath than the best you can get from the same chemicals in a single bath.

    Incidentally, if heating glycol gives you the willies, dissolve 10 g ascorbic acid in 10 ml hot water, add the 0.2 g phenidone, and add cold glycol up to 100 ml. It took me 15 seconds in the microwave to dissolve the chemicals. I doubt if that amount of water will appreciable shorten the storage life.
    Gadget Gainer

  4. #14

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    Quote Originally Posted by jdef
    Thanks, Ryuji. So, I just need to be sure there is enough metol present?
    No. It's not just any one thing, but the main point is that when you put one agent in A and another B, you shouldn't expect the same superadditivity just becauuse two agents are used. The outline I gave would tell you about the factors that could reduce the superadditivity effect. You should either figure out a way to take advantage of it, a way to overcome it, or abandon the idea of keeping two agents separated.

  5. #15

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Quote Originally Posted by juan
    OK, here's the potentially stupid question of the day. What about Pyrocat-HD as a two-bath developer? Why? Because with the SBR range where I photograph and the temperature at which I have to develop, I continue to have trouble with negatives with too much contrast for even Grade 2 Azo.
    juan
    Yes, you can use Pyrocat-HD as a two-bath developer. In fact, I have a professional photographer friend who swears by it, and says that for printing on silver papers it is the best thing to a silver bullet he has seen.

    Personally, I don't care much for the two-bath approach. I prefer to use weaker dilutions in combination with reduced agitation to tame the highlights.

    Whatever approach you take, however, you will have to test a lot to get it right.

    Sandy

  6. #16

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    Quote Originally Posted by jdef
    I tried omitting the ascorbic acid from the second bath, and saw a definite decrease in activity, which suggests to me that there is some superadditive effect. I'm sure you realize that I have no chemistry background, and am completely unqualified to conduct these kinds of experiments. I can measure chemicals, expose film, and measure densities thereof fairly accurately, which allows me to test simple ideas, and measure the results. Most of what you write is far enough over my head to be meaningless, although I do appreciate your consideration.
    Is it really the case that removing ascorbate from B decreases activity? It seems to me that you have enough metol in A. Removal of ascorbate would increase the pH of B. I am not too sure if the activity level goes down, unless you measure and compensate for the pH shift resulting from omission of ascorbate.

    I do realize that some of what I write are too much for many people, but if you see, at least, a piece of reality that what you read in Anchell and Troop or any other darkroom literature, including ones by famous authors, is oversimplified and sometimes misleading. Those authors aren't usually selling anything but their books, but you often see that those books have marketing hypes for the favorite techniques of the authors. I've been working with developer chemistry for several years, but as I understand more about it, what I realized was that there are many ways to achieve the same goal. (Henn of Kodak said the same thing in different words.) Of course, the simplest and most economical solution without losing reliability and robustness is the best solution (environmental load is another consideration), but in reality those authors sometimes prefer more complicated approach. Why? I don't know, but I bet that's something psychological. That's something I don't understand. (I'd rather talk about psychology and images, or mounting and framing techniques, for example, rather than psychology and unnecessarily cumbersome darkroom techniques. Darkroom work is transparent in good works anyway.)

    When I started photography I was very frustrated with the kind of information I could get on photographic chemistry. Internet was no good because there are some people who keep posting based on their speculations (but they somehow think truth) and there are even more people who keep copying the previous speculations, to amplify the noise. Soon, I realized that photographic chemistry is a highly specialized branch of chemistry which an ordinary chemist specializing in areas outside photography would not understand very deeply. After several years of catching up with 150 years of photographic technology, especially those recent results that clarify, support or dispute old theories, when I look at darkroom literature I have in my library, I realize good books containing few errors and misconceptions (I'm not talking about typographical errors or trivial errors) are some of those books that give concise instructions and relatively little far-fetched descriptions (and they give all you need to know to be a good photographer). I know one decent book written for science-savvy photographers, but besides this, your best bet for learning more about photographic chemistry is literature written for real photographic chemists. The gap is huge but if you want to get deeper understanding of developer chemistry, for example, I see no way around it. It's a big committment for a hobby, I know.

  7. #17
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,928
    Images
    65
    Ryuji's comment about photographic chemistry is correct.

    I would like to add that most of the real chemistry is so confidential that over half of it (my estimate) is art and not published, and therefore unknown in any literature. This extends the myth and error factor in published information on the net and in books.

    In addition patents are often misleading. They show a working embodiment, but the real salable product may be far from what is shown in the patent due to 'hidden' chemistry and 'hidden' technique not related to the use of the art disclosed in the patent. And let me add that this does not negate the validity of the patent. All the patent has to do is show that an invention is unique and not obvious and it must show a working example compared to the prior art.

    I think the best way to describe it is to say you are seeing, in a patent, a wing being disclosed from one evolutionary track when there are many. You see an airplane wing in the patent but the insect wing and the bird wing are equally functional but totally different in design even though all three lead to flight. Perhaps this might clarify how far disclosure can be from actual fact in R&D and mgf.

    The resemblance of the inner workings of R&D and the current state of knowledge compared to the published data is like looking at a man and a chimp. You see a resemblance, but in fact they are worlds apart.

    Ryuji's statement above, being so true, has often led to disagreements where I differ with him or Patrick Gainer. It seems to me that trivialization of the hidden art in photographic science and engineering is like me trying to, for example, become a biochemist or aeronautical engineer by reading a good science article and then going to my basement to build a working vaccine or a working jet plane.

    I respect both of their opinions, achievements, and knowledge. I simply cannot talk about a lot of mine, but there is a lot to talk about, a lot to be said, and a lot - more than anyone knows, still hidden behind the 'silver curtain' at Kodak, Ilford, Agfa and Fuji. None of the retired workers there are inclined in any way to talk about these matters at all, notwithstanding the fact that the knowledge will die out and is in fact dying out at the present moment. Each quarter, we get a newsletter with the current passings of our colleagues to the great 'darkroom of infinity'.

    At the present time, I am trying to formulate several developers and fix baths based on technology I know, and which may advance the understanding of the average hobbist by a modest amount. I am also working on several new emulsions which are simple makes intended for the hobbist as well, with economy and simplicity in mind. I hope to add appropriate manuals and teaching material to explain them completely so that an individual can extend them and customize them to suit their purposes better. I may even try to develop a photo system design workshop to teach others.

    I am also developing a method for inexpensive high quality hand coating which will yield a high return on expended emulsion in sizes of film and paper from 4x5 - 8x10. I need to hear if there is any interest in this as well. At present, I can only make 4x5, but the quality of the best approaches that of manufactured products. Soon, I will hopefully be able to do better.

    I will avoid using proprietary informaton in all of the above.

    I have gotten e-mail encouraging me to do this from those who have read my posts and have a similar interest. If you are interested, please e-mail me so that I can judge whether there is enough aggregate interest out there to continue. Emulsion experimentation as Ryuji knows, is expensive and very hard on a retired person's income. I need to hear from you all if it is worth going on.

    Thanks. Sorry for the blather to those not interested. I think that this puts into perspective though, some of the comments going on here, and also explains how I feel about what is happening to conventional photography. I am putting my time and effort into saving conventioal. Is it wasted? Are you interested?

    PE

  8. #18
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    It used to be that every photo shop had its trade secrets. Now there are few small shops where processing is done. "The Theory of The Photographic Process" is very incomplete because those who are most capable of completing it are bound to former employers to keep secrecy. One person with advanced degrees in chemistry and physics is at a tremendous disadvantage in trying to discover what the research departments of large companies have discovered and are keeping secret. Yet, when the photography industry yields to digital imaging, will those secrets be made known? It seems likely that if a company with secrets can no longer use those secrets to make a profit, the secrets will die. I'm not really paranoid, but I am dreadfully depressed.
    Gadget Gainer

  9. #19

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    No book is complete for that matter. You have to read original research reports written by scientists, patents written by product engineers and project managers, and analysis of products they actually make and sell. Patents are the lowest quality information source of these alone, but when combined with other sources, you'll get much clearer picture of what is being done in practice. Patents often list zillions of potentially useful compounds, millions of useful compounds, thousands of preferred compounds, hundreds of particularly preferred compounds, and they never tell you what they use, but if you use process of elimination from environmental regulations, occupational regulations, costs, synthesis methods of compounds in question, solubility, stability, etc., the obvious choices are limited and once the number gets cut down to dozen you can do tests and find out. Also, if you read LOTS of patents you'll get a vague picture of how their plants are set up, etc. and those fill in the very information that is kept blurry in the patents.

    Anyway, after 1990s, more is written abotu photographic chemistry in Japanese language than any other language, and journal of the society of photographic science and technology of japan STILL publishes research reports and review articles on silver imaging system. They are written by real scientists and engineers at Fuji and Konica specializing in the very topic, not low-level plant engineers and technicians, and they are rich of insights. Of course they don't give away commercially relevant information but that is not an issue. They are scientists and they are proud of showing their achievements to the public. The president of that society is Tani, one of the most famous scientists in photographic sensitivity (a branch of emulsion chemistry), who is also one of the high ranks of Fuji labs. Are they going to discourage publication of scientifically significant knowledge because those ex-scientists are retiring and starting second life as university professors? At least as I read from the pages of the journal, the trend is opposite. (And if a half of high ranks of the corporation is ex-scientists and ex-engineers who dedicated their life to silver halide photography, are they going to wipe out the products they worked on, so easily and completely, when the other half of business experts say to get rid of them?)

    In later half of the past century, those scientists gained access to equipment to analyze structure and other details of a single crystal in films and papers. Reverse engineering processing chemistry is also not that difficult. Trade secret approach is of not much use in this modern technological industry. Those Fuji researchers are publishing details of their achievements, including what methods they used to make emulsions, what they got, etc. with details of grain structures, performance analysis etc. Of course they always compared what they got against what Kodak got, so even if Kodak keeps it quiet, some info comes from the other end. More useful information is available today about certain things. If one firmly believes in silver curtain, a part of it resides in Rochester, and another part , his ignorance on existing literature.


    Quote Originally Posted by gainer
    It used to be that every photo shop had its trade secrets. Now there are few small shops where processing is done. "The Theory of The Photographic Process" is very incomplete because those who are most capable of completing it are bound to former employers to keep secrecy. One person with advanced degrees in chemistry and physics is at a tremendous disadvantage in trying to discover what the research departments of large companies have discovered and are keeping secret. Yet, when the photography industry yields to digital imaging, will those secrets be made known? It seems likely that if a company with secrets can no longer use those secrets to make a profit, the secrets will die. I'm not really paranoid, but I am dreadfully depressed.

  10. #20
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,928
    Images
    65
    Patrick, the authors of "The theory of the Photographic Process" are all dead. The only living researchers are not interested and are not encouraged to write about the details of their work.

    Ryuji, the Fuji work is as misleading as all others for what it leaves out. Believe me that the engineers at Fuji and Konishiroku will not talk openly at all. I have had lunches and dinners with Hrozo Ueda and Tadeki Tani, along with Yasuo Wakabayshi and others at intervals. Our companions were people like Paul Gilman from Kodak. Drs Tani and Gilman are known for their work on sensitization, and Dr Wakabayshi is reknowned for his work on lead dopants. In fact, I have an autographed copy of his textbook on photographic emulsions. (His name in Kanji is wrong in the book which distressed him very much).

    These sessions are very guarded.

    You talk about reading patents.

    I have read the original "Periodic Reports" on many of these subjects and have written over 100 myself. To understand a subject fully, you often must follow it from Periodic Report to Idea Memorandum to Invention Report, to the final Patent and then compare that to the Formula Transmission Document from R&D to the plant.

    Having done that personally and having written all of the above at one time or another, I am forced to say that I doubt that there is much of a gap in my knowledge or understanding of these topics. I should add also that the understanding of Kodak science by Fuji is far less than you might imagine, and the reverse is probably also true. I know this from discussions with the scientists at both companies who wrote some of the papers and books mentioned here.

    Theoretical knowledge gained from reading a book or patent is far removed from the actual practice of something. Try learning how to ride a bike or to swim by reading a book. If you try either with only book learning, you will need training wheels or be in the shallow end of the pool for a while before you gain any skill.

    Where the rubber hits the road is when they tell you they are going to make a full run of your film, paper or developer involving hundreds of thousands of dollars and weeks of scheduled time and your heart goes into your throat, and you hope and pray you got it right, and you don't know for sure - in spite of all the preliminary work, until people start using it and saying "hey, this is pretty good stuff".

    Where you feel bad is when you miscalculate pump speeds or valve timing and spray silver nitrate all over the floor in the making room and hold up all the work until the room is cleaned up. Or when you miscalculate viscosity and the coating winds up as a puddle on the floor of the coating machine and you have to spend the night with the night shift with your putty knife cleaning the machine with them.

    BTDT.

    PE

Page 2 of 3 FirstFirst 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin