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Photo Forum / Film Photography / Darkroom / October 2005PMK, ISO & ASA
First of all, can anyone confirm the tradeoff between ISO and ASA when using PMK Pyro? The recommended ASA's in the Formulary pamphlet are aprox 20% less than ISO's. Secondly, are there any pyro developers that give full film speeds? -Lew > First of all, can anyone confirm the tradeoff between ISO > and ASA when using PMK Pyro? The recommended ASA's in the > Formulary pamphlet are aprox 20% less than ISO's. > Secondly, are there any pyro developers that give full > film speeds? > -Lew Full film speed compared to what? The variation in speed among developers is around +/- 3/4 of a stop. This is less than the latitude of most films. The fastest speeds are gotten from optimum developers using Phenidone (Microphen, Xtol, T-Max), "normal" speeds from optimum developers with Metol and hydroquinone (D-76 and its many copies), lower than "normal" speeds from a variety of developers including extra fine grain developers when used full strength (Microdol-X, Perceptol, Kodak D-25) or some developers which either do not have the optimum amount of sulfite or which have to use bromide for fog suppression (Rodinal and many others). The first thee developers will yield about 3/4 stop more than D-76, the extra-fine-grain developers about 3/4 stop less, and Rodinal some intermediate value, perhaps half a stop. Pyro, by itself, is capable of good film speed but PMK may not give you this because its main goal is to produce a good stain image but with finer grain than the old and more active Pyro formulas. BTW, the ISO speeds are measured using a well controlled method but it does not specifiy a standard developer (the standard did in the past). The speed can be measured using any developer but the developer is supposed to be included with the film data along with the speed. The ISO speed is valid for the conditions of the test. If a different developer is used, or the film is developed to a different contrast (the ISO contrast is about right for contact printing and diffusion enlarging) then the speed will be different. Also, for black and white pictorial negative film there is virtually no safety factor (actually its 1.25) so exposures are just about the minimum that will yield good shadow detail. Nearly all negative films have enormous overexposure latitude so often the tone rendition of the film is improved by giving it a little extra exposure.  Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com > First of all, can anyone confirm the tradeoff between ISO and ASA when using > PMK Pyro? The recommended ASA's in the Formulary pamphlet are aprox 20% less > than ISO's. > Secondly, are there any pyro developers that give full film speeds? > -Lew One pyro developer that gives full film speed is 510-Pyro. Here's a link to the particulars: http://www.digitaltruth.com/techdata/article-stainingdev.php 510-Pyro fits Mr. Knoppow's description of speed enhancing developers, containing phenidone, but no bromide. This developer offers many benefits over PMK, including improved film speed, reduced grain, shorter development times, reduced general stain, compatibility with rotary processing, single-solution convenience, improved shelf life, and compatibility with extreme dilution/ reduced agitation development techniques. Jay > > [quoted text clipped - 21 lines] > > Hi Jay, Very interesting. I will have to try 510-Pyro. Thanks for the information. This shows that innovation in film-based photography is still strong! Francis A. Miniter > >>First of all, can anyone confirm the tradeoff between ISO and ASA when using > >>PMK Pyro? The recommended ASA's in the Formulary pamphlet are aprox 20% less [quoted text clipped - 24 lines] > > Francis A. Miniter No problem, Francis. If you have any questions or suggestions, feel free to contact me. Jay > improved shelf life, LOL ! I see ! You were pulling our legs ! I mean how can one take 3 of the least stable developing agents and make a more stable developer ? 510-PYRO TEA 75 ml Ascorbic acid 5 g <CRASH !> Pyrogallol 10 g <BURN !> Phenidone 0.25 g <FIZZLE !> TEA to make 100 ml John > > [quoted text clipped - 14 lines] >John > He says that the triethanolamine acts as a preservative. It is used in color developer formulations for that purpose, so I am willing to give it a try. The cost in chemicals for a test is fairly small. The only problem is the 150° F. temperature required, not insurmountable, just a pain. Am I going to need a pyrex container? I may take two test rolls and develop one in 510 Pyro and the other in PMK and see if I can visually detect any difference in the resulting developed film. Francis A. Miniter Francis: If you do make that test, please post your results. -Lew 510-Pyro is made up in TEA, and will not oxidize in the absence of water. When the concentrate is added to water to make a working solution, it becomes alkaline and acts as a developer. The 510-Pyro concentrate will last decades on the shelf, with no loss of activity. The 150F required to dissolv the constituents of the developer in TEA is only slightly warmer than the 125F recommended for making up Dektol , D-76, and many other commonly used solutions, and well below the boiling point of water. When comparing developers like PMK and 510-Pyro, it is important to test in a variety of conditions to see all of the differences. Using a rotary processor, or an extremely dilute solution and semi-stand development will show obvious differences. Other easily observable differences include film speed and general fog. Jay > 510-Pyro is made up in TEA, and will not oxidize in the absence of > water. When the concentrate is added to water to make a working [quoted text clipped - 13 lines] > > Jay So the oxygen (TEA = C6H15NO3) in it is bound ? If this is the case why does it darken when exposed to light or air as indicated in : http://www.jtbaker.com/msds/englishhtml/T5291.htm I will certainly give this a try sometime though. Sounds like a very interesting formula. John > > 510-Pyro is made up in TEA, and will not oxidize in the > > absence of water. In the absence of oxygen is correct. The oxygen in water is very much bound to the hydrogen. > So the oxygen (TEA = C6H15NO3) in it is bound ? If this > is the case why does it darken when exposed to light or air [quoted text clipped - 4 lines] > I will certainly give this a try sometime though. Sounds > like a very interesting formula. John The oxygen is bound. TEA, like H2O, will absorb oxygen. What of the freezing temperature, 72F, or separation at 60F? Mr. Gainer is the authority on the use of TEA in photochemistry. Perhaps the quest for immortality will continue. Dan ><snip> > > The oxygen is bound. TEA, like H2O, will absorb oxygen. > What of the freezing temperature, 72F, or separation at 60F? > Mr. Gainer is the authority on the use of TEA in photochemistry. > Perhaps the quest for immortality will continue. Dan I guess this developer does not get refrigerated like most. Francis A. Miniter I've had good luck with variations of Jay's developers in which I've substituted propylene glycol for some of the TEA. I then don't need to worry about my basement darkroom in NW Wisconsin that can get to 62°F in the depths of winter. I decided to get a good foundation with some pyro developers that have some history and user-base (PyroCat, WD2D+, Rollo, etc) and find that they all their attributes and find that PyroCat and the Rollo-TEA variant are especially predictable and useful but tend to lose a stop in true speed. I have had good luck with some limited testing of Jay's 510 and HyperCat and am now embarking on some more detailed testing and perhaps tweaking (PG blends, etc) and have not had a single episode that I would call a "failure". I'm using every opportunity to shoot black and white instead of color, even for "snapshot" situations as a way to get a comfortable, every-day situation sort of overview of the behavior of these concoctions. I also like the full speed nature of these 2 formulas. I recently sent Jay a shot I took of my son to show him the easy skin tone printing that HyperCat is allowing me. This is on HP5+ and prints almost grainless with a nice edge to details (eyelashes, etc) that give it very good accutance. This is downsized to 218K but it still shows the basic behavior better than I can describe.... http://webpages.charter.net/craigclu/eva7621.jpg These are 510's from a recent soccer game and are about 1/2 frame of a 300mm shot using HP5+ again... http://webpages.charter.net/craigclu/5Copy.jpg http://webpages.charter.net/craigclu/cfm7Copy.jpg It seems to handle the extreme light quite well and my scanning ability is showing its ugly head here, too. They printed easily in the darkroom and held good shadow and highlight detail, too. These are proofing scans, downsized for emailing but again, I think you can get an idea of the basic "look" of these developers. I like them and am going to pursue some additional sorting out and check out slower films now, too. >><snip> >> [quoted text clipped - 6 lines] > >Francis A. Miniter Craig Schroeder craig nospam craigschroeder com > I've had good luck with variations of Jay's developers in which I've > substituted propylene glycol for some of the TEA. I then don't need > to worry about my basement darkroom in NW Wisconsin that can get to > 62°F in the depths of winter. <big snip> Hi Craig, What proportions of TEA and propylene glycol did you find worked well? I have the same cold winter basement problem - Connecticut, plus the darkroom is beyond the insulation. Francis A. Miniter My notes don't jive with my memory and I was last dealing with this last winter so I'm now second guessing, I'm afraid. My recollection is that I was mixing the dry into the PG as it goes into solution easier in the PG than the TEA and at a lower temp. I use a magnetic stir/heater and I leave it at a moderate temperature allowing it to creep up slowly. I then add the TEA to the final total level of concentrate. I recall getting less discoloration when I didn't get so high in mixing temperature. I really need to revisit some of these mixes regarding which ones solidify as it seems to vary greatly with seemingly similar blends. Gainer's PC-TEA was going solid on me quite easily but Rollo-TEA didn't but I was getting paranoid about the issue as the reason I was getting involved with the TEA concentrates was for convenience issues. I've been more active lately because of renewed interest in the testing I've been doing but over time, I find that diversions, work, etc can sometimes make my darkroom visits sporadic and I liked the idea of very stable concentrates if gaps in time occurred between projects. I'm glad that Patrick G, Sandy King, Jerry Koch and Jay have done so much to further knowledge and interest in this direction. >> I've had good luck with variations of Jay's developers in which I've >> substituted propylene glycol for some of the TEA. I then don't need [quoted text clipped - 8 lines] > >Francis A. Miniter Craig Schroeder craig nospam craigschroeder com > The oxygen is bound. TEA, like H2O, will absorb oxygen. > What of the freezing temperature, 72F, or separation at 60F? > Mr. Gainer is the authority on the use of TEA in photochemistry. > Perhaps the quest for immortality will continue. Dan TEA certainly has peaked my interests though I still wonder why it darkens when exposed to light and/or air as documented in that MSDS I cited. In retrospect I probably won't bother with the pyro/ascorbate brew but it has given me an idea for a modification of something I've been toying with. John >>LOL ! I see ! You were pulling our legs ! I mean how can one take 3 of >>the least stable developing agents and make a more stable developer ? [quoted text clipped - 19 lines] > > Francis A. Miniter I might try something similar. I don't bother with ascorbates as their history indicates a strong likelyhood of unanticipated failure as seen with both Kodak's Xtol and Ilford's Ilfosol-S. John John, Xtol and Ilfosol-S are both aqueous stock solutions. Sudden death is not an issue for one-shot developers that need only last as long as the development time. As I've said, the 510-Pyro stock solution is extremely stable. I've never seen any TEA-based developer freeze, or separate, and my darkroom occasionally gets below 60F in the winter time. If my developer did freeze, I guess I'd warm it up. For those of you who live in cold climates, and worry about TEA freezing, you can make up 510-Pyro in propylene glycol, and a second solution of 10% sodium metaborate. In this two-solution form (call it 510-Pyro 2), it would be used like Hypercat. A 1:1:100 dilution of 510-Pyro 2 will give similar results at similar development times to the original, single-solution version. |
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