Fuji Neopan 400 - reciprocity failure data

Discussion in 'B&W: Film, Paper, Chemistry' started by xpista, Dec 7, 2005.

  1. xpista

    xpista Member

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    Hello,

    I cannot find any chart for the reciprocity failure for the long exposures for the Fuji Neopan 400 fillm as I can see the ilford films tech. data pdfs for example.

    I know that for the Fuji Neopan 100 Across there is almost none compensation needed for the long exposures. Is that true for the neopan 400 as well? If not, are you aware of some data/chart for the film you could point me to?


    Thanks in advance, Stefan
     
  2. clogz

    clogz Subscriber

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  3. clogz

    clogz Subscriber

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    Uh, uh got that wrong. No data concerning reciprocity here. Sorry about that.
     
  4. kunihiko

    kunihiko Member

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    1sec - 1/2 stop
    10sec - 1 stop
    100sec - 2 stops
    from fuji's data sheet. not much info.
     
  5. gainer

    gainer Subscriber

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    F-stop adjustments for reciprocity are OK if you have room. What if you are in the failure region with the lens wide open, or if you have set the f-stop for depth of field and don't want to change it? Those numbers for that film translate into the following equation with quite good accuracy.

    Tc = Ti + (0.3 * Ti^1.62)

    for use when you do not want to change f-stop.

    Tc is the corrected exposure time, Ti is the indicated time you read from your meter. The symbol * means "times" and Ti^1.62 means "Ti raised to the 1.62 power". These functions are on most pocket calculators.

    You will see that opening the lens one f-stop to correct for reciprocity at 10 seconds indicated time is not the same as doubling the exposure time. As soon as you open the lens, you have changed the indicated time from 10 seconds to 5. Thus the correction at 5 seconds indicated is 5 seconds. The correction at 10 seconds indicated is 12.5 seconds, making a total of 22.5 instaed of 20. At 100 seconds indicated, the correction is 1738, making the total 1838 seconds instead of 400.
     
  6. xpista

    xpista Member

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    Thanks for the formula, that sounds quite useful.

    But I need to ask:
    1. Where did you get the formula from?
    2. Are the coefficients general or do they apply only for Neopan 400 film?
    3. (more general) Having applied the time correction, do I need to shorten my development time accordingly or should I develop as I would based only on the ISO rating?

    Thanks, Stefan
     
  7. gainer

    gainer Subscriber

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    See my article "LIRF is Lurking F-Stop" at www.unblinkingeye.com. It is my formula, derived from data of Howard Bond and others. The exponent 1.62 seems to be the same for all films tested, within experimental accuracy. The "a" coefficient varies with film. In that article you will see a method for plotting the reciprocity corrections as a straight line on log-log graph paper.

    Bond found that for modern films, no adjustment of developing time is needed. Howard is a very meticulous experimenter as well as a fine photographer.
     
  8. xpista

    xpista Member

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    I am not able to find your article on the URL you provided. Neither a google search yielded any results. Could you share a copy of the article?
    Anyway - a lot of interesting reading on the www.unblinkingeye.com.

    Stefan
     
  9. gainer

    gainer Subscriber

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    Strange. I know it was there. Ed Buffaloe did not tell me he was removing it. I'll see what I can do. Essentially the same article was in Photo Techniques, but I don't remember the issue. Maybe if you searched that website you would find it.
     
  10. gainer

    gainer Subscriber

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    It was in Photo Techniques Magazine, 2003, vol.24, No.5 entitled "reciprocal Trade Agreement". It is too long to reproduce here. The previous issue had Howard Bond's report entitled "Reciprocity Revisited" from which I got the data I analyzed.

    If you want to email me your snail mail address, I can send you a CD.

    I am
    pgainer@rtol.net
     
  11. Lee L

    Lee L Member

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