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  1. #11

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    Bill,
    thank you for the explanation. It is much more clear now.


    Christoph,
    I think he refers to 21 steps stouffer because OP says that he uses 21 step http://www.apug.org/forums/forum44/8...-exposure.html

    mine 21 tablet step 11 = 1.54
    31 tablet step 16 = 1.57

    either way step number 11 on a 21 stouffer should be the same as step number 16 on 31 stouffer
    I think you are right, they should be close

  2. #12

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    Christoph,

    Can you verify that effective film speed -summary tab in FilmTestEvaluation_HP5.xls looks like on attached jpg?

    Click image for larger version. 

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  3. #13

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    wiedzim,...yes it is the same as the jpg isn't it a screenshot from my excel sheet? ;-)

  4. #14

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    thank you, yes it is from your spreadsheet, I was not sure if my excel 2010 displays charts correctly.

    Did you exposure hp5+ as 400 iso?

  5. #15

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    yes, i exposed hp5 at iso 400 because as Ralph states in WBM 2 "Assume the box speed to be correct and determine the right exposure with an average reading, or use a spotmeter for the medium gray bars. You can use the manufacturer’s recommended film speed, since the actual exposure is not critical as long as it is within 1 stop."

    But what/which number on a stouffer are the medium gray bars?

  6. #16

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    yes.. I had the same question. Very specific intrusion and suddenly in few places I was stuck.

    I'm wondering why effective film speed is so low in your test. Underexposure? Massive Dev Chart suggests 13 minutes as standard http://www.digitaltruth.com/devchart...ch&TempUnits=C based on your test N dev time is slightly more that 8 minutes.
    Maybe in that case dev times should be 5.5 8 11 16 22 minutes ?

  7. #17

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    yes i think i underexposed the film quite a bit. that's why i am asking on how to determine a "correct" exposure for the stouffer.
    i am hoping that Bill Burk can somehow explain the test results...and point out where i was stuck...so that the next test will work out...and i could get usable results...

    wiedzmin are you stuck in the same places i am?

  8. #18

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    I was more "lucky" with exposure but I would like to establish consistent and easy to repeat procedure. I also tried BTZS Plotter program, but I'm getting different results than using method from WBM 2

  9. #19
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    Quote Originally Posted by qualsound View Post
    Thank you Bill Burk for your answer...i have attached my (failed) test results from march for 120 rollfilm hp5+ and fp4+...could you please write your take on the results...i appreciate your knowledge and insight into the topic very much...as i am lacking there.... ;-)

    Thank you and best regards,...Christoph.
    Hi Christoph,

    Your tests look GREAT, I don't see anything but careful attention to detail!

    These look like camera tests, which includes flare. That messes with the toe, it never really gives you a low Base+Fog. So take the "effective film speed" results with caution.

    But AVERAGE GRADIENT for the development time is very good information that doesn't depend very much on the toe. You can use that information to make good development times decisions.

  10. #20
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    So the main point ... you don't get the film speed from the lightmeter setting. When you do film tests like this...

    You get the film speed from the box. The rated speed of fresh film in a standard developer, is very close to the "speed" of the curve that has an 0.62 average gradient.* So take that as "Zero" - your other speeds are relative to that box speed.

    When you develop less, you get less speed. Develop more and get more speed.

    *I see Ralph suggests 0.57 - close enough for you to use his numbers for practical purposes.

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