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  1. #41

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    Can we assume this method amounts to continous agitation? If so, it could help explain, for example, why adjacency effects might have been surpressed/reduced. It could also have an effect on speed as gamma would generally be reached sooner, with slightly less shadow development.

    Then again - as PE points out overanalyzing this experiment is problematic.

  2. #42

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    Quote Originally Posted by Michael R 1974 View Post
    Can we assume this method amounts to continous agitation?
    I don't think we can really infer anything, unless the reference cited has solid information.

    I would imagine that the "paddle" agitation is essentially a paddle or vane, or series of these, that sweeps past the test material. Given that the cost is reported as "high," I would expect that test runs could be configured in a number of ways. Possibly speed of paddle motion (rotation?) is variable, and possibly programmable for either continuous or any degree of intermittent sequences. So I dunno.

    I wouldn't worry too much about overanalyzing, as long as you enjoy doing it. (I'm sure PE has certainly done it himself!) Everyone knows the films tested are ~50 years in the past, so that you won't get any directly useful information. But it will help clarify your thinking on the subject, which will allow you to more clearly understand any such future tests as well as see their deficiencies.

  3. #43
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    I admit that I have over analyzed things but I did so either when I had all of the information or I could call on the originator of the experiment to answer questions.

    I am reminded of the circus elephant that escaped and ended up in the garden of a woman who had never seen one before. She called the sheriff and reported that there was a huge gray animal in her cabbage patch. When asked what he was doing, the old lady said "he is pulling up my cabbages with his tail and you would not believe where he is putting them"!!!

    Explaining this experiment is similar to my story. We just don't know what we have or what is going on. We cannot repeat the experiment exactly because those films don't exist and some of the actual conditions are missing such as agitation. And, BTW, that was just about the time that Kodak went to Nitrogen burst agitation which is not very expensive and is very vigorous.

    So, the best we can do is limp along speculating, which is what I am doing now. I wish I had paid more attention to this when I first saw it in the galley proofs. I might have asked Grant some questions back then that would help me post real answers here.

    PE

  4. #44
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    Quote Originally Posted by Michael R 1974 View Post
    And remember Altman and Henn were trying specifically to evaluate the effects of the Metol concentration and sulfite concentration.
    See, that's the problem. You change Sulfite concentration, but what you actually do is vary several parameters at once: alkalinity, buffering, solvent strength, oxidized Metol scavenging, ... and similar things happen when you add more Metol: contrary to expectations, activity goes down because pH drops so much.

    If you look at Sulfite, it's a terrible buffer at pH of 10 but quite strong between 6 and 8, and it is well known that pH drops locally in the emulsion during development. Since Metol develops down to pH 6 (see Haist), different buffering between pH 6 and 8 will have an impact on development and sharpness.

    What does this mean? Changing Sulfite in a developer will have different effects depending on buffering of other components, depending on developer pH, developer concentration and whatnot. The experiments published by Henn and Altman tell us what happens when we modify D23, but may not even tell us what happens if you lower Sulfite in D76.
    Trying to be the best of whatever I am, even if what I am is no good.

  5. #45
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    If you lower the sulphite in D76 you should get a touch better film speed, and improements in sharpness and finer grain and as a slightly better tonality. Later work showed that cutting the Sulphite to 80g/litre was a better blance, this approach was taken by Agfa in Agfa 44 (Agfa Ansco/Gaf 17), Adox Borax MQ and Ilford Microphen/ID-68.

    D76 is used FS in the tyests in the PDF.

    Ian

  6. #46
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    Quote Originally Posted by Ian Grant View Post
    If you lower the sulphite in D76 you should get a touch better film speed, and improements in sharpness and finer grain and as a slightly better tonality.
    If lowering Sulfite would have improved all key parameters of D76, one would wonder how Kodak could have missed that when they formulated it. Something is likely missing in this analysis.
    Quote Originally Posted by Ian Grant View Post
    Later work showed that cutting the Sulphite to 80g/litre was a better blance, this approach was taken by Agfa in Agfa 44 (Agfa Ansco/Gaf 17), Adox Borax MQ and Ilford Microphen/ID-68.
    None of the developers you list here are D76 with reduced Sulfite, they all have different compositions, and Microphen is not even an MQ type developer. Their low Sulfite content proves nothing, and looking at Promicrol and various Crawley developers tells me that 100 g/l Sulfite or even more never really went out of fashion.
    Trying to be the best of whatever I am, even if what I am is no good.

  7. #47

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    Quote Originally Posted by Rudeofus View Post
    If lowering Sulfite would have improved all key parameters of D76, one would wonder how Kodak could have missed that when they formulated it. Something is likely missing in this analysis.

    None of the developers you list here are D76 with reduced Sulfite, they all have different compositions (...)
    If you adjust the relative concentration of D96 or Adox to reach the same level of sulfite (100g/L), you obtain not so different formulas (more Borax + some Pot. Bromide):

    D-76
    Metol 2
    Sod. Sulfite 100
    hydroquinone 5
    Borax 2

    D-96 (x1,33)
    Metol 2
    Sod. Sulfite 100
    hydroquinone 2
    Borax 6
    Bromide 1

    Adox (x1,25)
    Metol 3
    Sod. Sulfite 100
    hydroquinone 5
    Borax 5
    Bromide 1

  8. #48

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    Sensitivity of developing agents to bromide is given as the bromide potential πBP in older texts. Each developing agent is compared to hydroquinone which is arbitrarily given a relative value of 1.0. The values of π range from 0.4 for paraphenylenediamine to 40 for Amidol in alkaline solution. The greater the value of π the less sensitivity of the agent to bromide. Mason contains a table of values and a discussion of the measurement method.
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  9. #49
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    Harold, those formulas are VASTLY different!

    To compare, you would hold HQ, Metol, and buffer constant as well as pH and then vary Sulfite only with no Bromide.

    Please remember that too many variables distort the results.

    PE

  10. #50

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    The origin of the term acutance as slope-of-the-density-distance-line at a knife edge, as used by Altman and Henn,is described in an article by Perrin on acutance here:
    http://image.eastmanhouse.org/files/GEH_1956_05_06.pdf
    They say that many tests showed the higher the acutance value the sharper the picture appears.
    However, as explained in Dr Henry's book it is now thought that adjacency effects also can change the perceived sharpness.Some confusion is caused as the combination of slope-of-the-line-acutance and adjacency effects never got a new name as Dr Henry suggested but is also called acutance.
    Measurements of slope-of-the-line acutance made by Altman and Henn were also made by Dr Henry and are in his book.These seem to be the only fairly readily available results.Altman-Henn are quite logical within the definition they use but their acutance measurements don't seem to have included any studies of the effect of agitation and their acutance is not necessarily perceived sharpness.
    When Crawley worked for Amateur Photographer magazine he used a microdensitometer to scan negatives of a series of lines starting thick and getting ever thinner.He seems to have extracted information about response of films giving some adjacency effects when he reviewd films.He never made a sudy of developers using this method, it might be possible.

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