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Thread: FP4+ rated @ 25 . . . reciprocity failure

  1. #1

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    FP4+ rated @ 25 . . . reciprocity failure

    Hey,

    I'm shooting long exposures during the day (20-40 min). I'm rating fp4+ at 25 (i've got -8 stops on the lens and I'm stopped down to f45)

    According to the reciprocity data I have a 2 min exposure should really be 17'21" and a 4min exposure should be 36'.

    HOWEVER when I process my film using that failure curve the film is WAY over exposed. (Even bringing the dev time down to 7' in Xtol 1:3 is too much--and results in uneven developing).

    So my question is this: If you rate a film lower do the reciprocity failure curves change? OR, is the curve data I have WACK?

    Thanks
    T

  2. #2

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    I would not drop the speed and then apply the rec failure. I would use your normal speed and then do the rec failure corrections.

    Test for your normalfilm speed with your developer of choice and then apply the correction.

    This might help your density problem.

    Where did you get the rec failure corrections?

    The uneven development is another problem. At the risk of being redundent, I have a tray processing technique that has worked for about 28 years. It is described in the Free Articles section of the View Camera web site

    www.viewcamera.com


    steve simmons

    steve simmons

  3. #3

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    Why are you shooting FP4 at EI25?

    Base the reciprocity correction on the EI you get with your developer, then if you want to place your shadows higher, do that using the reciprocity corrected time.

  4. #4

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    Quote Originally Posted by false_Aesthetic View Post
    Hey,

    .....

    According to the reciprocity data I have a 2 min exposure should really be 17'21" and a 4min exposure should be 36'.

    .....

    Thanks
    T
    A two minute exposure during the day sounds a bit odd? It seems to me that FP4+ rated at 25 and shot at f/45 should use something in the 1/2 to 1/5 second before worrying about reciprocity? Two minutes just sounds way long??

    cheers eh?

  5. #5

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    Hey,

    I read that article and process film as described... I'm pretty sure the uneven development comes from asking a little too much from the film... when I do normal stuff (tri-x in xtol 1:1) I have really even development. . . .

    I wanted to try and get around testing film but it kind've looks like I have to.

    The reciprocity chart I used is here: http://www.mkaz.com/photo/tools/reciprocity.html

    They're extrapolated from Ilford's publications.

    T

  6. #6

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    why an EI of 25, where did that come from?

    steve simmons

  7. #7

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    Quote Originally Posted by false_Aesthetic View Post
    Hey,

    The reciprocity chart I used is here: http://www.mkaz.com/photo/tools/reciprocity.html

    They're extrapolated from Ilford's publications.

    T
    The extrapolation "looks" ok given a quick once-over, but I still wonder about your initial exposure calcs. How do you come up with a two minute exposure during the day?I still think it should be in the order of 1/2 to 1/5 second. I'm just curious ....

    cheers

  8. #8

    Re: FP4+ rated @ 25 . . . reciprocity failure

    Okay- you rate FP4 at 25 asa. Sunny 16 says for full sunlight that would be about 1/30 (one thirtieth sec) at f16. Lets say its a little overcast, so 1/15 at f16. Now, close to f45 we need 1/2 second. Yes?
    First question- when you say you have -8 stops on the lens, is that really a stack of ND filters equal to 8 stops, OR is it a X8 red?? If so, a x8 red only needs three stops, so now we have f45 for 4 seconds, and with reciprocity (from the ilford data sheet) that means about 10 seconds.
    If you really have 8 stops of ND, then f45 for 1/2 sec does become two minutes. I also shoot long exposures on PanF and FP4- for a calculated two minutes I would give about five (I double and add half again). For a calculated 4 mins I'd give 10.
    Just wondering, what are you looing to achieve? Do you need very long exposures to blur motion, or lose people??

  9. #9

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    EI 25 sounds very strange for this film, as does the 17 1/2 minute exposure time with a metered two minutes. Using the generic reciprocity tables that John Sexton hands out in his workshops you would get about a 4 minute time with a 2 minute meter reading. His tables have always been right on for me with HP5+ and TMax 100. Something seems to me to be wrong somewhere, either with the 25 EI or the 17 1/2 minutes or both.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  10. #10

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    Re: FP4+ rated @ 25 . . . reciprocity failure

    I am wondering if this is a serious question or a game of gotcha. There are too many unknowns and to much conflicting info and the questioner is not answering any of the questions, such as

    WHY AN EI OF 25?

    what does -8 on the lens mean?

    maybe we should stop tryng to help until he/she provides some real and complete info.

    steve simmons

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