ILFORD FP-4 PLUS; CORRECTING FOR RECIPROCITY FAILURE

Discussion in 'B&W: Film, Paper, Chemistry' started by wskmosaic, Apr 2, 2012.

  1. wskmosaic

    wskmosaic Member

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    Does anyone know if reciprocity failure correction computed for Ilford HP 5 Plus will apply to Ilford FP-4 Plus?

    Ilford's data sheet on these films, which declares correction factors for all its films to be equivalent, was never meant to be a precise guide, and is very old.

    In addition, does anybody know, for either of these films, what the reduction in developing time for each range of exposure increases to compensate for reciprocity failure?

    tnx

    Warren
     
  2. Oren Grad

    Oren Grad Subscriber

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  3. Shawn Dougherty

    Shawn Dougherty Member

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    I go by the Howard Bond data for HP5+, it has worked well for me so far.
    For FP4+ I have been using the Kodak reciprocity chart for general black and white film (Not the TGRAIN CHART) and it has been working great.
    Don't forget to decrease development as well!
     
  4. dnjl

    dnjl Member

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    I use the following formula to calculate reciprocity compensation for classic Ilford films (PanF+, FP4+, HP5+):

    exposure time^1.48

    For example, a 15sec exposure after correction will result in a 55sec exposure. I found this works well.

    I don't remember where I picked this up, but thanks to whoever came up with it originally.
     
  5. wskmosaic

    wskmosaic Member

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    Re: Recip Failure and FP-4 Plus

    Thanks for the quick and thoughtful responses.

    Oren: I have read Bond's article. I trust him implicitly and rely on that article--or as much of it as I can handle. Which is why I'm so down on the Ilford figures.

    Walter: I believe that ^1.48 is the Ilford formula precisely. I can't imagine how it can work for all the films they list it for. I'm afraid I'm not going there.

    And Shawn:
    I'll take a look at those Kodak figures, but I'm curious to know why you've never given the Bond figures a run with FP-4+. If you ever do, I'd love to hear about it. I think Bond might, too.

    tnx

    Warren
     
  6. wskmosaic

    wskmosaic Member

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    Quick further question, Shawn:
    At what ASA do you shoot FP-4+ and what is your normal developer and development time?
    tnx
    Warren
     
  7. Shawn Dougherty

    Shawn Dougherty Member

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    As far as I know Bond did not work with FP4+ or I certainly would.... If I'm missing it somewhere please point it out!


    I rate FP4+ @ ISO 64. However, I tend to error on the side of more exposure. I am developing FP4+ in Pyrocat HD at 1:.5:100 (note that B is POINT FIVE ((.5)). 8 Minutes for N. I develop 4x5 in small tubes gently rolling them in water. And I stress the importance of using N- development in various degrees for reciprocity corrected exposures.

    Edit. HERE is a link to the Kodak graph I have been using for FP4+, it is on page 3.
     
    Last edited by a moderator: Apr 3, 2012
  8. wskmosaic

    wskmosaic Member

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    AND THANKS FOR THE KODAK GRAPH; I HAVE THEIR DATA.

    AND THANKS FOR ALL YOU HELP.


    WARREN
     
  9. Rick A

    Rick A Subscriber

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  10. Regular Rod

    Regular Rod Member

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    I use the chart that ILFORD supply but I print it with more grid lines to make it easier to read across. It has never let me down. Here's my pdf of it to print off, cut out, laminate and keep with the exposure meter.

    RR
     
  11. Rick A

    Rick A Subscriber

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    Their product, their research.
     
  12. ic-racer

    ic-racer Member

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    http://phototechmag.com/black-and-white-reciprocity-departure-revisited-by-howard-bond/

    That article seems to have a serious flaw. He is testing for aperture correction and plotting time correction. The entity that tie aperture to time is reciprocity! When he converts his results from aperture to time correction his equation (1 stop light = 1 stop time) is only valid if reciprocity holds true at all times! If you convert his table back to f-stop correction, then it is a valid table for what he is testing (dim-light photography at 1/4 second).
     
    Last edited by a moderator: May 31, 2015
  13. Ian Grant

    Ian Grant Subscriber

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    There is no way to produce an accurate Reciprocity table because the variables in light type, intensity, spectral composition, scene contrast etc are just too wide. It makes a difference if it's Daylight or Artifical light particularly Tungsten where a film has a lower EI anyway.

    It's far better to do your own personal tests in the lighting conditions you intend to work with. Failing that the Ilford chart will get you close it probably has a degree of safety factor built in.

    Ian
     
  14. Regular Rod

    Regular Rod Member

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    I can only repeat that "It has never let me down"...
    :wink:
    RR
     
  15. Shawn Dougherty

    Shawn Dougherty Member

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    In my experience the most accurate info I've found (info that I've tried and has led me to good results) is the Howard Bond data... (who did not test FP4+).

    The info provided by Ilford is, as stated earlier, a big generalization which they have used for years on multiple films. Following it led me to overexposure. Testing yourself (or at least bracketing like crazy and keeping careful notes) is your best bet. Of course it can be very time consuming...