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Thread: Anomaly in exposure testing

  1. #1

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    Anomaly in exposure testing

    Just when I thought I had exposure and development nicely set, a conundrum arose which I hope someone may be able to help me resolve. Since there are a number of variables, I am attaching a zip file of a Word document with a full explanation, since it will otherwise make a very long post.

    In brief, it pertains to exposing a set-up twice, placing two materials of different reflectance on the same zone and getting results about a stop and a half apart.

    I'd be grateful if someone can explain it or suggest a new test to isolate the issue.
    Attached Files Attached Files
    Philip U.

    Sine scientia ars nihil est.

  2. #2
    ic-racer's Avatar
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    Re: Anomaly in exposure testing

    Expose for the lower values and set the higher values when developing and printing. So, if there is a dark shirt that needs a certain minimal value to retain texture, set that object and the others fall. Don't base a scene's exposure on a highlight value (unless exposing reversal materials). Some Zone Systems are 'black box' devices to help photographic artists. A photographic scientist will have a full understanding of the way paper and negatives behave when exposed to light and developer can complete the picture.

    Here is a good start: https://www.kodak.com/uploadedfiles/...y_workbook.pdf

  3. #3

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    Re: Anomaly in exposure testing

    Thank you the link, though I have no access to sensitometric equipment. As I wrote in the attachment, I had already tested successfully for Zone I, and ran the last test placing the black shirt on III in one exposure and the tan towel on III in the next.
    Philip U.

    Sine scientia ars nihil est.

  4. #4
    Jac@stafford.net's Avatar
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    Re: Anomaly in exposure testing

    Test to your heart's content, but to be happy you might consider a far simpler modified Zone System. Never, ever has a properly made exposure trumped a compelling image.

    When explaining one's process requires more than a page of text, it is likely your effort is a distraction from making images. Maybe scientific imaging would suit such a person. Only academics appreciate verbosity more than substance.
    Last edited by Jac@stafford.net; 1-Jan-2018 at 18:45.

  5. #5

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    Re: Anomaly in exposure testing

    I regret, Jac, that you choose not to share some your photographic expertise with me. I am sure I could benefit.
    Philip U.

    Sine scientia ars nihil est.

  6. #6
    Jac@stafford.net's Avatar
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    Re: Anomaly in exposure testing

    Quote Originally Posted by Ulophot View Post
    I regret, Jac, that you choose not to share some your photographic expertise with me. I am sure I could benefit.
    I'm sure I cannot help except to repeat my approach which is to understand the fundamentals and make photographs, then if you find compositions, photographs you like but are unsatisfied with tonalities, then look to technical exposure/filtering/development improvement. Making a compelling photo is the hardest part. Working from pure chemistry outward has not worked for anyone I've known in fifty years of photography.

    Very best,
    Jac

  7. #7

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    Re: Anomaly in exposure testing

    Thank you; I understand you better now. At the risk of being less than concise, I will elaborate this way: I agree entirely on compelling imagery; as in great music, a musician may give a performance of stunning technique devoid of art. My circumstances do not allow me to dedicate my life to art as I would like. My intensive studying of great art, and attempts to produce some echo of their wonder for decades, is what drives me. Having been obliged to put down my cameras about 13 years ago for financial reasons, I am now in the process of returning to serious personal work. Because of the challenges new aspirations are taking me, I think it obligatory to regain, and supersede my previous level of command of the craft as I pursue greater artistic aims as well. My technical question arose in this context.
    I attach one portrait to at least indicate my genuine intent.
    Attached Thumbnails Attached Thumbnails Amelia Robinson 1990.jpg  
    Philip U.

    Sine scientia ars nihil est.

  8. #8

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    Re: Anomaly in exposure testing

    two guesses, but only guesses.

    I) The beige towel has a greater capacity to throw light, as such it throws light in many directions and causes flare in the lens/camera/film. thus a brighter zone III in the print.

    II) You may be on to something when thinking about infrared 'pollution'. The reflectivity of the two objects is probably very different, reflecting different parts of the spectrum. the Bright towel may be baised towards, say red light, while the black t-shirt may be baised towards blue. The films sensitivity to those two colors is different and so what the meter says should be Zone III is different for the two objects.


    I wonder, if you place both items at zone VII what happens?
    I also wonder if reciprocity failure is doing something here, eg. not enough exposure of the low values. ( I assume the exposure to place the black T shirt on Zone III is longer than the exposure for the towel on Zone III).
    ~nicholas
    lifeofstawa
    stawastawa at gmail

  9. #9

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    Re: Anomaly in exposure testing

    Thank you for your detective work, stawastawa. In response:

    I think it unlikely that flare would lead to the 1.5-stop difference in these circumstances. The lens is, I believe, multicoated, and has not shown significant flare in situations with brightly lit light surfaces.

    Reciprocity departure was not at issue here, neither exposure being greater than 1/2-second.

    Your idea of placing both materials on a higher zone is interesting and probably worth a try, to see if the same issue persists. I'll have to wait for a brighter day to avoid reciprocity.

    As mentioned, the meter is supposed to have extra infrared filtration built in, but it's hardly a new meter and this may be a variable. Whether it could account for the wide discrepancy, I don't know.

    Again, thanks for taking time with this.
    Philip U.

    Sine scientia ars nihil est.

  10. #10

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    Re: Anomaly in exposure testing

    to test the metering see if you can locate some different meters to compare.
    ~nicholas
    lifeofstawa
    stawastawa at gmail

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