F-stop test strips

Discussion in 'Enlarging' started by wiseowl, May 29, 2004.

  1. wiseowl

    wiseowl Member

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    I want to start doing my test strips using the f-stop method. So far I'm able to work out 1/2 stop increments, not exactly difficult even for my poor maths ability. However this has been a little coarse and I think it would work even better if I used 1/4 or finer steps.

    Is there a formula, or rule of thumb for calculating these small increments, or some other resource, such as a chart or table available? I know there is a timer which supports this feature but that is outside of my budget constraints, at least at the moment.

    Cheers

    Martin
     
  2. JHannon

    JHannon Member

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  3. jpersson

    jpersson Member

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    I have a trick for 1/3 stops if you happen to forget your math and your charts. Look at the light meter ISO settings; ISO 100 for 1 second, ISO 125 for 1.25 seconds etc. It is not high math but it is close enough for me.
     
  4. naaldvoerder

    naaldvoerder Member

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  5. Eric_Fr

    Eric_Fr Member

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    The formula is very simple :

    n
    Tb*2
    with Tb : Base Time
    n : Stop fraction ( -1, -1/12, ...,0, 1/12, +1)

    Eric.
     
  6. Eric_Fr

    Eric_Fr Member

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    you must read "2 power n" in previous reply.
     
  7. Jorge Oliveira

    Jorge Oliveira Member

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    There's one guy in the NET that made a freeware program for a Palm that will do that.
    I've designed for him an interface so the Palm can control an enlarger.

    I do not know his site, but if someone is interested, pls PM me and I will send his email.

    Jorge O
     
  8. GreyWolf

    GreyWolf Member

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    Here is another pdf chart that prints on a single piece of paper.

    My f-stop chart

    Kind Regards,
     
  9. JHannon

    JHannon Member

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    It can't get any simpler than just printing out the chart. I used this until I bought a F-stop timer. Nice job on your chart GreyWolf..

    John