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  1. #301

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    Hypersensitization of film was still being done for astrophotography in the 1990's. I do not know whether this practice still continues but I would suspect that it still does.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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  2. #302

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    Quote Originally Posted by Gerald C Koch View Post
    D-76 suffers an increase in pH due to oxidation. This has been known for a very long time. Various modifications have been proposed to the original formula to provide better buffering such as D-76d which contains 8 g/l each of borax and boric acid. The change in activity led me to abandon the use of D-76 decades ago. I personally would not describe this developer as being reasonably buffered.
    You are mixing two different issues here.

    Any solution will increase pH if some of the constituents react to generate base in the solution. You are merely stating that D-76d is more heavily buffered than D-76. Buffer is not all or nothing deal. It is a matter of degree, and the question is what degree is sufficient for the application. If you don't keep D-76 stock solution for a long time the original formula is sufficient.

  3. #303

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    Quote Originally Posted by Ryuji View Post
    That particular case, everything is reversible reaction and nothing leaves the system so it doesn't matter as long as the end product and pH meet your needs.
    Thanks. That's very good to know.
    When working with concentrates versus directly mixing into water, the order will change, and it's good to know the end-result will be the same.

    Mark Overton

  4. #304
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    Quote Originally Posted by Thomas Bertilsson View Post
    http://www.apug.org/forums/forum216/...-negative.html

    This will help you shape your tone curve.
    Thanks, Thomas, I am fully aware that "stand development" (I put it in quotes because agitation does take place every so often) combined with weak dilutions can reduce contrast in a neg. The important point is, though, that not all developers respond to this in the same way, I would imagine a strongly buffered developer does this much less than a poorly buffered counter part, all other things the same. Rodinal is known to work extremely well with stand development. Its other big plus is that it is very well characterised after so many decades of heavy use. There are, however, hopefully some additional ways of achieving a flatter curve in the highlights which also work with devs more suitable for e.g. Delta 3200 (I have nothing against TMZ except that it doesn't come in 120 format).

    PE has written about swelling agents for the gelatine like urea which foster development and grain growth. It would be interesting to find the opposite of these swelling agents so less fresh dev reaches the silver halide. In the same thread he wrote that sulfite regenerates HQ, so putting in less or no sulfite into the mix may also help me get closer to my goal (no idea whether it does the same with phenidone/ascorbic acid). Lots and lots of silly ideas which show how little I understand but which indicate to me that there is something which gets me there. Assuming I don't care about grain size and dev durability I can safely play with the sulfite content (I know, I know, pH value ...).

    PS: I learned today how spoiled and dumbed down I am from using premade developers. It took me hours to get Na2SO3 and borax to dissolve in water, same problem of course with phenidone in propylene glycol. I also learned the hard way that it is not feasible to specify 0.058g of a substance which is sold in pellets Oh well, noob lessons learned . I will hopefully have everything mixed until tonight (writing this while the borax dissolves) and can report back later.

    PPS: Mark, some of the substances you specified come with varying amounts of H2O bound to the crystal grid. For now I assume you mean Na2BO2 * 4 H2O when you specify "Sodium metaborate". Please tell me if this is indeed the case.
    Trying to be the best of whatever I am, even if what I am is no good.

  5. #305
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    Sodium Sulfate is one of the best anti-swell agents for gelatin.

    PE

  6. #306
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    Quote Originally Posted by Rudeofus View Post
    Thanks, Thomas, I am fully aware that "stand development" (I put it in quotes because agitation does take place every so often) combined with weak dilutions can reduce contrast in a neg. The important point is, though, that not all developers respond to this in the same way, I would imagine a strongly buffered developer does this much less than a poorly buffered counter part, all other things the same. Rodinal is known to work extremely well with stand development. Its other big plus is that it is very well characterised after so many decades of heavy use. There are, however, hopefully some additional ways of achieving a flatter curve in the highlights which also work with devs more suitable for e.g. Delta 3200 (I have nothing against TMZ except that it doesn't come in 120 format).
    That article is not about standing development. It is about using agitation as a tool to shape the tone curve. 1m agitation intervals will cause a different tonality than 5m agitation intervals.
    This works well with Rodinal, but Xtol works equally well, as does Edwal 12. (Those are the developers I have used this way, and have experience with using this technique).
    Rodinal works very well at the 1+50, or 1+25 dilution too using this technique.

    I posted the link, because Ryuji said it was very difficult to alter the tone curve because it was very much a characteristic of the film used. I counteracted that comment by showing that you can override the tonality of some films (TMY-2, Tri-X 400, FP4+, TMX, Acros, Delta 3200, which have long straight curves) and create a shoulder by slowing down agitation. I do it myself every single time I develop film.
    "Often moments come looking for us". - Robert Frank

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  7. #307
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    @PE: can you give me any details about quantities to use for the effect I want? Is the number from the dark room cookbook (105g/1l) a good starting point?

    @Thomas: I understand the difference between stand developing and what you suggest in your article. Stand development is one extreme which would bend the characteristic curve a lot, frequent agitation is the opposite extreme which creates a straight(er) curve, and your suggestions cover the range in between to fine tune the outcome. I'm also surprised that Ryuji questioned the shapeability of the characteristic curve since I have read too many times that different developers yield different curves.

    @Mark: you recipe worked, I developed for 12 minutes (attempted 2 stop push), agitated every 1/2 minute and got reasonable looking negatives. I'll try to print a few of them on Wednesday and will report what I find especially with regard to speed and highlights. Please note that I am aware that exposing film with the builtin meter of my Rollei 35s, pushing it two stops and then looking at the result is not the recommended way of evaluating a developer I do have a densitometer at my darkroom so if questions about my negatives arise I can take some measurements (e.g. min and max density).
    Trying to be the best of whatever I am, even if what I am is no good.

  8. #308
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    You can use Sulfate at 25 - 100 g/l. The effect depends on concentration and you can salt out your developer and get crystals forming in it if you use too much. Also, the effect may be smaller than you wish.

    PE

  9. #309

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    I have done some testing of PC-TEA where the developer is dilute but quite high amounts of sulfite added and I could not get grain as fine as Xtol(or DS-10,Mytol,E-76).It seems to me quite likely that the high phenidone(or derivative), ascorbate and borate in these latter contributes to the fine grain.Therefore the concentrate has to be high in phenidone,ascobate and borate.The chemistry gets to the limits of what is known,esp wrt the formation of glycol borate complexes and their dissociation,when making these concentrates.It's quite a project.

  10. #310

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    Quote Originally Posted by Thomas Bertilsson View Post
    I posted the link, because Ryuji said it was very difficult to alter the tone curve because it was very much a characteristic of the film used. I counteracted that comment by showing that you can override the tonality of some films (TMY-2, Tri-X 400, FP4+, TMX, Acros, Delta 3200, which have long straight curves) and create a shoulder by slowing down agitation. I do it myself every single time I develop film.
    Well, the sensitometric data shown at your link does show some visible difference in the curve, but if you compare that to the shoulder of Verichrome Pan or Panatomic-X (which are generally referred to as films with shoulder) or even Delta 3200 or TMZ, you are not even halfway there. I would not state that effect as if you can switch one type into another.

    The best way to obtain the "shoulder effect" in film characteristics today is to use paper emulsion with toe, and use print developer that does not trim the toe.



 

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