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  1. #1
    Jim Fitzgerald's Avatar
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    Densitometer readings?

    Let me first say that I do not know much if anything about this machine but I'm willing to learn. I guess I'm more of a Weston type. It works like magic and I don't know how. I have a Xrite 329 densitometer. I read my Pyro negs on the blue channel and here are some of the reading I've gotten. These are my first 8x20 negs and I'm trying to figure out how this relates to my printing paper. I have one neg that is good to my eye. It is Bergger 200 shot at 80 and developed in Pyrocat HD in trays for 12 1/2 minutes at the 2:2:100 dilution. The readings are .87 and 1.92. Is the range DR 1.05? I have no idea how this relates to my paper that I'm trying to contact print this on which is Forte Polygrade V. I know there are many questions the people who know about all of this have for me. So fire away. I know this film is not the best to expand contrast. Would I just increase the development time? I have another test negative that I developed for 16 minutes and the readings are from 1.35 to 1.68? The exposure for this neg was about 2 1/2 minutes and I should have reduced development probably. How do I find the paper curves to match the neg to? Am I backwards in my thinking? Like I said I'm interested in learning but I'm a slow learner so be patient. Help me understand the process. This is something I've always been curious about but I need a simple explanation. Thanks to all.


    Jim

  2. #2
    gainer's Avatar
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    Were I in your shoes I would contact print the two areas you measured with small pieces of the paper you plan to use. The blue channel readings would be more appropriate for graded paper, but sample prints on the Polygrade will help you calibrate your densitometer. OTH, maybe I'm all wet in assuming that Polygrade means variable contrast.

    The problem with the densitometer is that you need to make a print in order to calibrate it! The value of the densitometer is that once you have it calibrated, you can apply some factors that will let you read the DR next time, but if you are using variable contrast paper, the factors will vary with the printing filtration, so you may need a chart of meter factors vs filter setting or filter number.
    Gadget Gainer

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    Jim,

    I suggest you read one fine book that will help you understand these readings and curves : 'Beyond the zone system' by Phil Davis.
    http://www.amazon.com/Beyond-Zone-Sy.../dp/0240803434
    and of course you can find it on e**y.com

    This book will guide you step by step to understand film and paper curves, how to obtain and use them for your purposes.

    See also : http://btzs.org/

    Marc
    Last edited by Marc .; 10-30-2007 at 02:08 PM. Click to view previous post history.

  4. #4
    Jim Fitzgerald's Avatar
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    Quote Originally Posted by gainer View Post
    Were I in your shoes I would contact print the two areas you measured with small pieces of the paper you plan to use. The blue channel readings would be more appropriate for graded paper, but sample prints on the Polygrade will help you calibrate your densitometer. OTH, maybe I'm all wet in assuming that Polygrade means variable contrast.

    The problem with the densitometer is that you need to make a print in order to calibrate it! The value of the densitometer is that once you have it calibrated, you can apply some factors that will let you read the DR next time, but if you are using variable contrast paper, the factors will vary with the printing filtration, so you may need a chart of meter factors vs filter setting or filter number.
    Pat, thanks for the response. This has always interested me. The Forte Polygrade V is a variable contrast paper. I have done some Azo prints that I can measure along with some Kentmere graded prints. So, when I measure the prints what channel do I use? Then when I compare the print readings to the negative readings how do they relate? I hope this makes sense? I'm sure I'm confused but that is normal for me.

    Jim

  5. #5
    Jim Fitzgerald's Avatar
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    Quote Originally Posted by Marc . View Post
    Jim,

    I suggest you read one fine book that will help you understand these readings and curves : 'Beyond the zone system' by Phil Davis.
    http://www.amazon.com/Beyond-Zone-Sy.../dp/0240803434
    and of course you can find it on e**y.com

    This book is will guide you step by step to understand film and paper curves, how to obtain and use them for your purposes.

    See also : http://btzs.org/

    Marc
    Marc, I think reading and research is the answer. Thanks.


    Jim

  6. #6
    Photo Engineer's Avatar
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    The zone system is only 7 points on a 21 point scale. Each zone is 1 stop from the adjacent steps. The complete 21 point scale is encompassed by a normal film with a range of density from 0.1 to 3.0 under normal conditions. The slope is about 0.6 for negative films.

    Paper has a range of 0.1 to 2.0 under the same conditions and as a negative, it has a slope of 2.5 (grade 2) and 1.5 as a print.

    So, the zone system is a small subset of the H&D curve and a small subset of the full range of a film.

    PE

  7. #7
    Jim Fitzgerald's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    The zone system is only 7 points on a 21 point scale. Each zone is 1 stop from the adjacent steps. The complete 21 point scale is encompassed by a normal film with a range of density from 0.1 to 3.0 under normal conditions. The slope is about 0.6 for negative films.

    Paper has a range of 0.1 to 2.0 under the same conditions and as a negative, it has a slope of 2.5 (grade 2) and 1.5 as a print.

    So, the zone system is a small subset of the H&D curve and a small subset of the full range of a film.

    PE
    Ron, thanks for this. Let me digest it a bit so I understand. I think a step wedge is in order so I can "see" what is going on and how it relates. Sorry for being thick headed but some of this stuff confuses me. I appreciate your expertise and knowledge in these areas.


    jim

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    Quote Originally Posted by Jim Fitzgerald View Post
    Marc, I think reading and research is the answer. Thanks.


    Jim
    Jim,

    Here is also a link to a Kodak workbook on sensitometry (this is the name of the thing...)
    http://www.kodak.com/US/plugins/acro...y_workbook.pdf

    Phil Davis' book covers the same subject, explaining each concept and suggesting exercises.

    The effort to read these books is well worth it !

    Best,

    Marc
    Last edited by Marc .; 10-30-2007 at 02:29 PM. Click to view previous post history.

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    I have a Macbeth densitometer and a Stouffer calibrated scale so I can make sure the densitometer is reading correctly. In the back of the book "The New Zone System Manual" White - Zakia - Lorenz, is an excellent explanation relating the paper to the film and both to the Zone System. In the Appendix, I, Calibration with Densitometer and Graphs explains step by step how to take measurements and plot the curves, very nice to know for contraction and expansion. Flair, reciprocity and other topics that come into play are also covered. It's a book well worth having.

    Stouffer site: http://www.stouffer.net/TransPage.htm

    Curt
    Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand

  10. #10
    Photo Engineer's Avatar
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    The Kodak reference is excellent. It explains the whole thing in detail.

    I used to think (with no derogatory thoughts intended) that the zone system was densitometry and sensitometry for dummies.

    Sorry. My failing entirely!

    PE

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