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  1. #11

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    Are the following the formulae you refer to?
    See the end of the post by Michael Gudzinowicz:
    https://groups.google.com/forum/?hl=...om/zp8vBn9P8Nw

  2. #12

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    Yes those are the formulae (didn't check each one for correctness but they look right).

  3. #13
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    sounds like a great test. how can i participate?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  4. #14

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    Well, I guess first it would be good to discuss some of Altman and Henn's findings - even though they are somewhat outdated in the specifics.

    Your feedback on any of this would of course be of great value, Ralph. Hopefully we'll get some feedback from PE and others too.

    What I'd really like to do is re-run a similar test with some current films. It's a lot of work but could be interesting to do. The problem I have is I don't have the equipment required to determine RMS granularity and make objective acutance measurements. At the very least one requires a microdensitometer.

    Will post the summary today and see what happens.

  5. #15

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    My guess is that Altman and Henn measured acutance by the old slope-of-density-versus-distance method on film exposed under a knife edge.As mentioned in The Film Developing Cookbook and in Controls in Black and White Photography,this does not take into account adjacency effects which affect the perceived sharpness.

  6. #16

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    Alan - it would be strange if that were the case (although it certainly could be the case) as in Haist the study is quoted in the section about both solvent action and edge effects. Although it is not clear how the measurements were made.

    Attached is a summary I put together for discussion - if someone can tell me how to get it into this thread without screwing up all the formatting (I typed it in MS Word), I'd like to put it in the text here instead of as an attachment.
    Attached Files

  7. #17
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    The triad around which a developer "rotates" consists of speed, grain and sharpness. Hank and Dick worked on this triad looking at how the variables affected all three items. And so, Sulfite, Buffer, pH, etc were all fair game. This work was done to lay the foundation of the next generation of developers. Dick and others had wrapped up D76, then Dick went on to make HC-110, and the next generation was done by Dickerson (X-Tol). FWIW, one more generation is lying in the Kodak archives somewhere.

    Also, FWIW, the written paper may differ considerably from the internal report. Much material was always edited out of publications due to the confidential nature of the material being deleted. This was also the case with Grant's book. Grant bemoaned the fact that many things were cut from his early drafts. (I was one of the cutters! But, Grant and I are still friends!)

    Anyhow, if there was anything worth money in that work it was either confidential and remains so, or it was patented.

    Now, it is not impossible to design a developer for all films. In fact, at the time I left Kodak, D-76 was the release developer for production runs of all films. All films were tested against aims in D76 and either passed or failed. So, all films went through one developer. And, looking at Kodak's developer table and time of development curves, you can see results that are good for a number of films.

    The only developer that is not able to work across films, is a two bath developer due to different grain types and emulsion thicknesses. You have to optimize things for every film or the two baths will not work right.

    Other critical items are pH and buffer capacity along with agitation.

    Now, back to Dick and Hank. They were doing this work in about 1960 or earlier with films that do not exist today. You may think that this makes the work obsolete, and it does in a sense. But consider what I have said.... All release tests are done with D76.

    I hope that this ramble sheds some light on things.

    PE

  8. #18
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    More light to shed! I was reading and writing when the last post was made with the PDF file.

    Where did it come from? What publication?

    Now, on to tests.

    For grain we ran RMSG (Root Mean Square Grain) tests in which a microdensitometer read density at every step in a step wedge. The "noise" was grain and was plotted as a function of grain vs the original step wedge densities. AFAIK, Kodak has never published any of these plots.

    The sharpness is measured by making X-ray and white light exposures with 1000mm, 100mm, 10mm and 1mm apertures at varying densities and then plotting the result in frequency. These are posted on the Kodak web site. We did both negative and positive imaging to show flair and fill. A bright white image flares outward, and a black image with a while surround is filled in. I have charts for both here to run tests when I get a good HD developer.

    X-Ray and white light were used to show the effects of turbidity in the coating.

    Hope this helps too.

    PE

  9. #19

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    Interesting - thanks for the added info and background as always, Ron.

    The tables I wrote out are from Haist. Unfortunately I don't know where I'd be able to get the original research paper, which no doubt would shed some light on certain aspects, although Mr. Bill who responded earlier in the thread seems to have a copy.

    So would the acutance measurements you describe indeed factor in edge effects?

    What fun I would have doing a rigourous series like this with current films!

    Any insight on why the acutance-type formulas in the test gave such poor results with Tri-X - where all three of the triad variables were worse than the baseline (D-76)?

    Or why a mushy developer like D-25 would give Panatomic-X the same acutance as D-76 1+1?

    By the way apologies again for having to attach my summary as a PDF. When I tried repeatedly to copy the text into the body of the reply, I couldn't get any of the spacing to work properly and the data was impossible to read.

  10. #20
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    Yeah, APUG does not like formatted data! Bummer.

    Ok, you do not have to have the best developer to get a benchmark on the properties of developer ingredients. So, this particular developer series might well be worse than D76. And, if the developer is too far out of line, it can reorder results of all films. I've seen that where a coating passed all specs and I ran it through other developers the coating failed in several parameters while giving the accepted curve shape and speed.

    So, I cannot comment on what they got, but I'll bet that the reasons and a lot more facts were explained in internal reports!

    The sharpness tests plotted as response vs spatial frequency and is MTF (Modulation Transfer Function). These tests include all edge effects and that means bad or good.

    PE

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