Weston Model 715 Exposure Meter & Lumens

Discussion in 'Lighting' started by baumgrenze, Apr 24, 2010.

  1. baumgrenze

    baumgrenze Member

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    For the grand sum of $2.50 I purchased a classic (1939-1945) Weston Model 715 Exposure Meter. It seems to be working; at least in bright daylight it follows the f16 rule.

    I would like to use it for an unorthodox purpose, to measure the illuminance of some light sources described by corporate marketing departments as "equivalent to a 60W bulb.)

    Does anyone reading this question have a rule-of-thumb correction factor to convert the classic Weston reading into lumens or lux?

    If this is the wrong sub-forum for this question, please point me to the proper one.

    thanks,

    baumgrenze
     
  2. MartinCrabtree

    MartinCrabtree Member

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    1 footcandle=10.74 LUX.

    The classic Weston scale for Masters I,II,II reads in footcandle.A test for the meter is on a sunny day w/o clouds/haze point the meter to the northern sky between 10AM-2PM.Should read approximately 320.Clouds,haze and shade will cause erroneous readings.
     
  3. baumgrenze

    baumgrenze Member

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    Martin,

    Thank you for the prompt, informative response. My Weston is what some descriptions have called a Master 0.

    It is 10:15 AM on a clear, sunny, northern-California day with a decent blue sky (not high Sierra blue, but blue) and I get a reading of 75-80 for the unobstructed northern sky, suggesting a factor of 4 difference from what it intended.

    I do not have a manual. I cut my photographic 'teeth' on an OM-1 and then an OM-4, so I have no experience with a light meter. I have vague recollections of my mother using one in conjunction with taking photos with her Stereo Realist camera in the 1950's. Is the dial below the meter coupled with the internal circuitry so that it has an impact on the reading? Mine is set as follows. The main arrow is pointed at 100. The window opposite it is almost complete red and reading EMULSION.

    I've forgotten, is there a simple way to attach a small jpg file to a forum post? "A picture is worth 1000 words."

    Thanks again,

    baumgrenze
     
  4. MartinCrabtree

    MartinCrabtree Member

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    Yeah it seems you have a first of the master series.I sent my Master II off to Quality Light Metric.It was repaired the within hours of his receipt of it.Cost $88 usd with return shipping.Can't say enough good about him.Real nice guy who know his craft and how a business should be run.I suggest you get yours repaired and calibrated if you wish to use it.
    I prefer the earlier Masters for the direct readout in candlefeet.I am attempting to grasp the Zone System so that works best for my feeble grey matter.I got my manual here.Along with a bunch of other info.No the dials are just used to calculate exposure with the luminance read by the meter.I'm new to this as well but have been devouring all I can by reading a lot.

    Here's something I ran across that would be handy if you're a zone user.

    Oh and you can upload images from your computer using the manage attachments section.Click "go advanced" and poke around you'll find it.Or you could host via flicker,photobucket,ect. and hotlink to it.
     

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