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  1. #1

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    exposure adjustment for change in enlarger height

    Hi, somewhere I have a table that does a quick approximation for the change in exposure when the enlarger is raised or lowered. I know the formula, but the table would make things easier. I have looked online and can't find one. Also, I assume that the measurement is made from the film plane to the top of the easel.

  2. #2
    wildbill's Avatar
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    www.vinnywalsh.com

    Check out my low volume sheet film tanks.

  3. #3
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    here's one from Ralph Lambrecht that I found a long time ago on his Darkroom Magic site

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    Quote Originally Posted by samcomet View Post
    here's one from Ralph Lambrecht that I found a long time ago on his Darkroom Magic site
    I can offer this;hope it helps a bit.
    Attached Files
    Regards

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

  5. #5
    samcomet's Avatar
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    ooopppss Ralph beat me to it before I could upload the same image. Thanks mate!!!!

  6. #6

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    There was once a very useful table here on APUG given to us by a APUGer as a link You simply entered the before and after column heights and the original exposure and it produced the new exposure.

    I bookmarked it but the site has gone, alas. Maybe the originator would consider resurrecting it, assuming he still participates here?

    pentaxuser

  7. #7
    wildbill's Avatar
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    Quote Originally Posted by samcomet View Post
    ooopppss Ralph beat me to it before I could upload the same image. Thanks mate!!!!
    I guess no one reads before they post these days. I posted a link to the same chart. Yeah, the pdf is better.
    www.vinnywalsh.com

    Check out my low volume sheet film tanks.

  8. #8
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    sorryBill
    Regards

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

  9. #9

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    A bit of mental arithmetic can achieve the same result. Suppose that you have a test filling 5x7" and want to make a print on 16" paper, the new image area is measured to be about 11 1/2"x16" (ignoring small borders). So the increase in exposure is (11 1/2x16) divided by (5x7), (184/35), which works out to 5,26 and therefore 5,26 times the original exposure time, as a starting point.

    Given the large change in size you might also want an increase in contrast, and probably to change the exposure by a few tenths of a stop from the test - but the different print areas are illuminated by the same light-source, so the starting-point increase (or reduction, if making a smaller print) in time works like this.

    If you make 'minimum-time-for-maximum black' style contact-sheets, and use an enlarger as the light-source, then you can also estimate a starting point for any size print from the time used for your contact-sheet.

  10. #10

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    Quote Originally Posted by RalphLambrecht View Post
    I can offer this;hope it helps a bit.
    Many thanks. It does indeed help.

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