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  1. #1
    hortense's Avatar
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    RECIPROCITY BLACK & WHITE FILM

    It appears Digital Truth has posted incorrect reciprocity data according to my experience with exposures less than 15-minutes. Have NOT tested Ilford for reciprocity but used their formula meter reading ^ 1.49.

    BLACK & WHITE FILM
    Digital Truth for ALL B/W film (http://www.digitaltruth.com/techdata/reciprocity.php)
    1 sec reading: expose 2 sec and N-10%
    10 sec reading: expose 1 min and N-20%
    100 sec reading: expose 20 min and N-30%
    Kodak for 320TXP
    1 sec reading: expose 1 sec and N-0%
    10 sec reading: expose ≈18 sec and N-1
    100 sec reading: expose ≈4-min and N-1 1/2
    Ilford
    1 sec reading: expose 1 sec and N-0%
    10 sec reading: expose 30 sec and N-10%
    100 sec reading: expose ≈15 min ^1.49=15 min ≈N-30%
    [FONT=Times New Roman]MAC[/FONT]

  2. #2
    colrehogan's Avatar
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    I would just download the tech sheets for each film you are using or plan to use and they include reciprocity information.
    Diane

    Halak 41

  3. #3
    hortense's Avatar
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    Quote Originally Posted by colrehogan
    I would just download the tech sheets for each film you are using or plan to use and they include reciprocity information.
    Kodak 320TXP and Ilford reciprocity data are documented by each company. More specifically Ilford states that there film reciprocities are based on Uncorrected Time or Meter Reading seconds ^1.49. However, if you have some information that would substantiate or correct what Digital Truth has claimed it would be helpfut to forum viewers. Perhaps other viewing this verify?
    [FONT=Times New Roman]MAC[/FONT]

  4. #4
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    My co-author conducted a reciprocity test lately, but the data is not evaluated yet. So I can't post anything right now. Nevertheless, I have a working reciprocity chart for Kodak films and it matches the above table closely.

    One factor needs to be considered. What is the color temperature of the low-light condition, which is causing the reciprocity failure? Film has a very different sensitivity to blue, green or red light. If we are facing a tungsten low-light condition, the reciprocity chart made with dim daylight data will give false results.

    Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.
    Regards

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

  5. #5

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    Quote Originally Posted by RalphLambrecht
    Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.
    Dear Ralph,

    Oh dear! Giving away trade secrets!

    Couldn't agree more!

    Cheers,

    Roger

  6. #6
    hortense's Avatar
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    Quote Originally Posted by RalphLambrecht
    One factor needs to be considered. What is the color temperature of the low-light condition, which is causing the reciprocity failure? Film has a very different sensitivity to blue, green or red light. If we are facing a tungsten low-light condition, the reciprocity chart made with dim daylight data will give false results.

    Remember, film is very forgiving to over-exposure. When in doubt, just double the exposure. It won't hurt.
    Thanks Ralph. I did not realize this factor was involved. I thought that the increased exposure requirements took this into consideration - but, you tested - that settles it. Sounds like you and a coleague are doing some in depth reciprocity testing. I would be nice to do better than a very broad estimate. Keep us informed as you get more data?
    [FONT=Times New Roman]MAC[/FONT]

  7. #7
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    Hi Hortense,

    The data on our site comes from many reliable sources, but there can always be errors or inconsistencies. The reciprocity data is a guideline only and testing needs to be done with individual films.

    We are happy to accept any improvements to our site, and will credit all contributions, so if anyone can supply better data, then please send it to me and we will make it available on our information pages.

    --Jon

  8. #8
    hortense's Avatar
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    Quote Originally Posted by Digitaltruth
    Hi Hortense,

    The data on our site comes from many reliable sources, but there can always be errors or inconsistencies. The reciprocity data is a guideline only and testing needs to be done with individual films.

    We are happy to accept any improvements to our site, and will credit all contributions, so if anyone can supply better data, then please send it to me and we will make it available on our information pages.

    --Jon
    Jon - You site is fine. Pardon my comments - not intended to throw spears. We value the service your site provides. I was hoping others would chime in with the reciprocity data they have used successfully.
    [FONT=Times New Roman]MAC[/FONT]

  9. #9
    hortense's Avatar
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    Jon - Here is what I have successfully used for TriX. Ilford calculations are
    Meter Readiing in seconds ^1.48.
    [FONT=Times New Roman]MAC[/FONT]

  10. #10
    hortense's Avatar
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    320TPX

    Here it is.
    Last edited by hortense; 09-19-2006 at 07:27 PM. Click to view previous post history.
    [FONT=Times New Roman]MAC[/FONT]

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