Determining Illuminance from Camera Exposure

Discussion in 'Exposure Discussion' started by Steaphany, Sep 11, 2011.

  1. Steaphany

    Steaphany Member

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    Here's my first question:

    I've searched through this site and found there has been extensive discussions on pre-exposure, but I have not been able to find exactly what I need. A means to calculate the Illuminance from a traditional ISO, Shutter Speed, Aperture exposure setting.

    Film is documented in the luminous exposure curves as density versus lux seconds.

    < Embedding an example graphic produces an error >

    If my pre-exposure light source produces a set exposure, how do I convert this into lux to then turn down the exposure to something specific, such as 0.0032 lux in my pre-exposure ?
     
  2. BrianShaw

    BrianShaw Member

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    Many meters have a table in their manual that allows conversion of light value to lux and or foot-candle.
     
  3. Christopher Walrath

    Christopher Walrath Member

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    Do a google search for the SLIT rule or the SLAT rule. This shows EV combos for shutter speed and aperture and also for the combinations of ISO and light additive values.
     
  4. Stephen Benskin

    Stephen Benskin Member

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    Go to this thread.

    http://www.apug.org/forums/forum37/85217-k-factor-relevant-me-should-i-cancel-out.html

    I put together a detailed explanation of exposure from the average daylight/sunlight illuminance, to the original subject, to the exposure meter, to the camera exposure, to it's placement on the film, and how it works with film speed.

    I've since made it into a pdf file, but it's too large to upload here. I'll be happy to email it to anyone interested.

    I've attached a sample page.
     

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    Last edited by a moderator: Sep 11, 2011
  5. BrianShaw

    BrianShaw Member

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    Interesting. since i did the google search, here is the result:

    http://www.jollinger.com/photo/meters/other/ev_system.html
     
  6. Steaphany

    Steaphany Member

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    I found the same page and it linked me to the Exposure Value article on Wikipedia that has the necessary formulas and example tables to help me derive what I need to determine pre-exposure settings.
     
  7. BrianShaw

    BrianShaw Member

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    Did you find this one too? Doug Kerr writes some amazing material. I think he is a PhD... or some kind of genius.

    dougkerr.net/pumpkin/articles/APEX.pdf