Print Magnification / Conversion Formula!

Discussion in 'The Darkroom' started by romie, Oct 20, 2003.

  1. romie

    romie TPF Noob!

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    Enlargement Question
    Having the exposure time and the lens opening of a enlargment and wanting to changing the height size of a print say from a 8x10 print @ f16 @ 00:15 exposure time to a 11x14 what is the formula to make the change from one size print to another?


     
  2. oriecat

    oriecat work in progress

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    Well I don't know what the formula is, but according to a spreadsheet that Will gave me, I think it would be 26.75 seconds, provided I did everything right, which is no guarantee.
     
  3. romie

    romie TPF Noob!

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    Thanks Oriecat!
    Somewhere I read or was told that times 10 (X10) is the formula for calculating the time needed in making a print larger timewise with the same f-stop of the original print.
    I will do some test to see. :roll:
    romie- Boston, MA.[/u]
     
  4. motcon

    motcon TPF Noob!

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    Orie has it correct.

    why bother asking if you are going to do tests anyway?

    a 10x rule? u realize that takes you to nearly 3 minutes of exposure from 15 seconds? common sense should tell you to not even waste a sheet of paper on it.
     
  5. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Will is right. Don't worry about crazy math. You need to be doing a whole new test print for the 11x14 anyway. When you increase enlargement, you decrease contrast, so you're basically starting over. Don't skimp on the test prints.
     

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