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  1. #11
    RalphLambrecht's Avatar
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    Quote Originally Posted by Lars Daniel View Post
    I have searched high and low, but I can´t seem to find any info about FP100-c behaviour in long exposures. I know it is not really meant for long exposures, but I almost took it for granted that there was some useful info floating around somewhere.
    Anyone?
    i have something close enough:
    Regards

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

  2. #12
    Lee L's Avatar
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    Quote Originally Posted by giacoboh View Post
    It's been a while,
    could you please write the formula you were referring to?

    I found this but my result doesn't match your:

    Relative film speed = d*(t+1)^(p-1)

    [p=Schwarzschild exponent; t=exposure time; declared film speed]


    I'm trying to estimate correct exposure for my pinhole camera (f/315) which use FP-100 with a metered time of about 4 minutes.

    (Sorry for my bad english)
    Thanks,
    Giacomo
    Your English is far better than my Italian.

    That's the correct formula for adjusting film speed, but use the following to adjust exposure time:

    corrected exposure time in seconds = (t+1)^(1/p)-1

    where t is the metered exposure time in seconds and p is the Schwarzschild exponent. I should probably also state clearly that the metered exposure time in this formula is at the declared film speed 'd', not at the relative film speed from your Schwarzschild formula.

    Lee
    Last edited by Lee L; 04-11-2012 at 11:16 AM. Click to view previous post history.

  3. #13
    RalphLambrecht's Avatar
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    the equation is correct,but how do you know the value for p?
    Regards

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

  4. #14
    RalphLambrecht's Avatar
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    use this table for tmax100,and note that measured 4 min turn into 40 minutes!
    Regards

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

  5. #15
    Lee L's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    the equation is correct,but how do you know the value for p?
    Ralph,

    I've answered in a .pdf format to preserve the table.
    Hope this helps.

    Also included a chart for metered times up to 120 seconds, which is of course extrapolating from Fuji's data.
    I believe all the math to be correct, but can't vouch for the accuracy of Fuji's data, and I haven't included the density of the filtration Fuji suggests. As always, test for your own conditions and adjust.

    Lee
    Attached Files
    Last edited by Lee L; 04-12-2012 at 08:22 AM. Click to view previous post history.

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