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  1. #71
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    Bill, thanks for the reminder. I had forgotten that Mike wrote that chapter.

    Michael, Crawley was both right and wrong. The older emulsions had buried iodide and were slower. They had little edge effects. The newer, double run emulsions, had surface iodide and thus had edge effects. In addition, modern or high speed emulsions have very efficient acutance dyes in them to aid in sharpness over and above the enhanced edge effects.

    These effects are often difficult to see without the tests I described, except as enhanced sharpness.

    The surface iodide seen in modern emulsions is also the reason why it is difficult to see enhanced sharpness with the older Crawley formulas which used iodide to enhance sharpness. These Crawley formulas relied on rapid adsorption of iodide on the grains surface and then release during development to cause mild edge effects.

    You are in Montreal. This is not all that far from Rochester. Get a few APUT members together and then get GEH to lend us their classroom!

    PE

  2. #72

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    More from Crawley's article, Amateur Photographer 30 March 2002:

    "....Kodak calls the effect 'acutance' and introduced a new range of films in the 1960's designed for acutance-notably a new Panatomic-X emulsion. Other makers followed or took steps to improve definition. That prompted a number of high and maximum definition developers to exploit them."
    "...truly major step came in the 1980's with 'high tech grain' emulsions, such as T-Max and Delta...... About the same time it became possible to adsorb chemical molecules to the surface of grain which further enhanced performance...........However, such materials changed the developer outlook. The presence on the surface of the the halide grains of improver chemicals, as well as greater light capturing area, has made the traditional fine grain developer's solvent action on the emulsion grains undesirable. The result has been a new generation of non-solvent developers such as T-Max, Technidol, Ilfotech, Ilfosol, FX-39.......As films became finer grained, attention turned to obtaining better sharpness of the subject's main features and crispness in definition of fine detail."

  3. #73

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    Interesting that in both the Altman/Henn study and Henry's tests Panatomic-X seemed to do best in D-25 when it came to both acutance and grain (with a reasonably small speed penalty vs D-76).

    I'm not too sure about that list of "non-solvent" developers for tabular grained emulsions. T-Max and Ilfotec are solvent developers (Ilfotec more than T-Max). Kodak considers D-76 and XTOL (both solvent) to give the highest sharpness with TMax films, and Ilford considers ID-11 (D-76) at least as sharp as Ilfotec for use with Delta films.

    I have to admit I have never taken Crawley's chemistry quite as seriously as many people do. Certainly Anchell and Troop consider him a genius but I don't know...

  4. #74
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    Just about every photographic (emulsion) effect is one of adsorption. So, Crawley is somewhat off base with his comments quoted above. Adsorption has been a tool used for years. As for solvent developers, the results posted above show that solvent developers can work, and not too badly. OTOH, the surface iodide (and other adsorbed species that were patented in about 1970) were the things that did the trick and which also obviated the utility of the Crawley developers, and those of many others.

    In other words, he said many of the right things for the wrong reasons and many wrong things for the right reasons!

    PE

  5. #75

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    Erwin Puts was an authority,he more or less agrees with Crawley. Towards the end of this article:
    "Good average results you can get with Xtol but if you need to expand in one direction or the other (granularity or definition) specialist developers are required."

    http://web.archive.org/web/200504050...tateofart.html

  6. #76

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    I don't know, Alan - I'm more or less with Puts on the required resolution in prints (speaking strictly in lines/mm), which is essentially consistent with Perrin and others (ie 10-20 l/mm). But not so sure about his comments on developers. To be fair, the article doesn't go into the details of what sharpness and acutance are, but I find the recommendations a little simplistic. Suppose one dilutes XTOL to 1+1 (as recommended by Kodak) or 1+3. In terms of acutance I question how one can do materially better in the sharpness department with specialist developers when it comes to general purpose films. It seems to me based on most of the data I've seen what you might get with dilute Rodinal or Neofin are more pronounced edge effects, but with a proportionately large penalty in graininess. So when Puts says "...expand in one direction or the other (granularity or definition)", I'd argue based on the data the potential for going in the definition direction vs XTOL (or diluted XTOL to be more precise) is quite limited. Particularly when one then combines image structure characteristics with tone reproduction, "good average results" is quite the understatement regarding XTOL or D-76.

    Interesting discussion, folks. Appreciate the feedback.

  7. #77

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    Also thanks to Mr. Bill for the Kriss reference in James. Even at my best with calculus (which was some time ago at this point) I imagine most Kriss's work would be over my head. Unfortunate.

  8. #78
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    Look at the developer tests posted a few pages ago. Henry's data does not show huge differences with some specialty developers. It seems as if D76 is just about as good as anything or at least it is hard to get excited over anything there.

    PE

  9. #79

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    PE,

    Not wanting to charge in, but from reading through this thread there may not be a strong or real reason to look towards so-called specialist film developers in the vast majority of cases; and that D-76 or XTOL etc. are the best option?

    Tom

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    Learned a lot today.


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