f-stop printing calculations

Discussion in 'Darkroom Equipment' started by Todd Barlow, Feb 23, 2006.

  1. Todd Barlow

    Todd Barlow Subscriber

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    What is the formula that is used to calculate the times shown in the various f-stop printing sheets?

    For example
    If the base time is 8 sec:
    +1 stop = 16 sec how do you arrive at +1/2 stop = 11.3 sec?

    Todd
     
  2. Bruce Osgood

    Bruce Osgood Membership Council Council

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    ------------------------------------------------------------

    http://unblinkingeye.com/Articles/TestExpo/testexpo.html

    This should give you a good starting point.
     
  3. Lee L

    Lee L Member

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    Todd,

    I made up my own tables in a spreadsheet. If you can handle openoffice or Excel spreadsheets, the attached .zip file has both formats (done in openoffice) that produce an f-stop printing table. You can look at the formulae used in the spreadsheet to get an idea of how it works.

    I just taught two 6th graders the basics of B&W, and since they'd just learned the basics of geometric progressions with camera stops and shutter speeds, f-stop printing seemed very natural and logical to them. I now use an RH Designs timer rather than these charts.

    Lee
     

    Attached Files:

  4. vet173

    vet173 Member

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    Thanks Lee, that is great. Helps us what got problems with cypherin.
     
  5. lee

    lee Member

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    RH Designs Stopclock timer will do this for you and is much more accurate but the trade off is it is more expensive.

    lee\c
     
  6. Marc Leest

    Marc Leest Member

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    Simple

    it would be T x 2^+f
    (^ means to the power)
    So in your example
    it would be
    8 x 2^ +1 = 16
    8 x 2^+0.5 = 11.31

    M.
     
  7. Lee L

    Lee L Member

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    For those without a spreadsheet program, an f-stop timing table for printing is at: www.largeformatphotography.info/articles/f-stopTimingAdv.pdf
    This is a .pdf file of a page from Way Beyond Monochrome.

    I didn't mention it in my earlier post, but openoffice is free and very capable, and available for Windows, linux, solaris, BSD, and Mac OS-X. See openoffice.org

    Lee
     
  8. PieterB

    PieterB Member

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    Yes I saw the .odt in your zip-file :wink:
     
  9. joeyk49

    joeyk49 Member

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    Todd:

    Thanks for asking the question.


    Posters:

    Thanks very much for answering.


    Joe
     
  10. Gerald Koch

    Gerald Koch Member

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    Do a google, there are several places on the web where you can download the images to make a calculator. Or buy a new/used copy of the Kodak Darkroom Guide which has one.
     
  11. Todd Barlow

    Todd Barlow Subscriber

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    Thanks all... you have come through once again.

    Todd