Old Exposure Meter and New(er) Film Speeds

Discussion in 'Exposure Discussion' started by JFB, May 4, 2014.

  1. JFB

    JFB Member

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    Folks,

    I have a question regarding the ASA (ISO) ratings of today's films (B&W negative film) when used in conjunction with old exposure meters. I have a GE DW-68 serial No. R02119 which I've been using for a while now with decent results, I believe it's giving accurate readings. Tonight I read that back when my meter was built there was a safety factor of one stop built into the film ratings. I probably read that years ago and completely forgot about it.
    So should I actually be setting the exposure index number to the next smaller number on my meter, e.g. to 50 when I'm using a film rated 100 ASA? Is there any adjustment I should make for color negative film or transparencies? (I haven't shot any slides since the 1980's, but I've been thinking about getting some again.) Also just to double check-the dial on my meter reads"EXPOS INDEX" on the outer ring, so those should be ASA numbers, not the older GE film numbers?

    Pax,
    John
     
  2. MartinCrabtree

    MartinCrabtree Member

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    When I use an off camera meter it's a 60+ year old Weston Master II. I found some literature from the maker on film speeds and use their recommendations w/great results. It has been reconditioned and calibrated by Quality Light Metric so I trust it and the results show that trust is warranted.
     
  3. AgX

    AgX Member

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    The film speed figures have changed. Not the meters.
     
  4. Jim Jones

    Jim Jones Subscriber

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    The Weston Master II used Weston speed ratings developed prior to the ASA system and which were similar, but not identical, to ASA numbers. The Master III used ASA numbers. Google for Weston film speed if more information is desired.
     
  5. momus

    momus Member

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    No matter how it was calibrated in the beginning, it's changed now. I highly recommend calibrating it with a camera that you know exposes perfectly, in various lighting conditions, or using a known meter that you know is accurate. Having owned a few of these, I am pretty sure of what you will find. In good light it will give good readings (assuming the cell is still good, and you calibrate it w/ a known meter). In low interior light it will be useless. Even at factory specs, a selenium celled meter is not good for low light.

    I have a bigger, heavier meter that is more accurate inside, but in 99% of my lighting needs, the Sekonic L 188 meter below does the job, and it's so small and light you don't even know it's in your pocket, unlike your GE. It takes readily available 1.5V button batteries that last 1 to 2 years.

    http://www.ebay.com/itm/Sekonic-Aut...eter-with-Case-and-Instructions-/251519311687
     
    Last edited by a moderator: May 5, 2014
  6. Jim Noel

    Jim Noel Member

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    There are charts of equivalent rating speeds on the web. Google to find one.
     
  7. JFB

    JFB Member

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    Gents,

    What I'm wondering is: Will I get better results if I exposed ASA 100 film using an ASA 50 setting on my (older) meter?

    When film manufacturers dropped the safety factor in their film rating did meter manufacturers alter the numbers on the meter dials?

    Pax,
    John
     
  8. Jim Jones

    Jim Jones Subscriber

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    No.
     
  9. Xmas

    Xmas Member

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    Your meter should be ok use the datasheet ISO.
    Check the zero light setting is zero and your shutter speeds are normally out...
    in 61 they only changedthe mono speeds
    Trix was 200 it became 400 lots of people still use 200...
     
  10. Bill Burk

    Bill Burk Subscriber

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    If you rate a 100 speed film as 50 you might be giving yourself a safety factor. In that sense you can get better negatives. Slides, probably better at rated speed.

    But you might already have a safety factor working in your favor: You can see my thread regarding shutter testing where I just found my 500 setting is really giving me 1/125th second exposure.
     
  11. Terry Christian

    Terry Christian Subscriber

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    They didn't.
    Film, by virtue of it's being a product with an analog response curve, has a bit of leeway built in -- B&W and color negative more, color transparency less.
     
  12. Xmas

    Xmas Member

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  13. JFB

    JFB Member

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    Momus,

    Thanks, I decide to give the Sekonic a try. I arrived today. The previous owner made a notation in the manual on the (battery pg) "SR44" which I guess is the modern battery equivalent to the G13 JIS The battery test, with a new battery, puts the needle a bit beyond the blue test square, and it give a very different reading than the GE DW-68, about four stops difference when "tested" under a bulb. I'll have to test them outside later and shoot a test roll.

    Pax,
    John

    P.S. an unintended bonus of the purchase: it came with a really nice GE leather case for my DW-68.:D
     
    Last edited by a moderator: May 15, 2014
  14. E. von Hoegh

    E. von Hoegh Member

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    When you compare the meters, find a large - larger than the field measured by the meters - evenly lit surface to meter. Your two meters likely have different acceptance angles.
    Old selenium meters can be dead accurate, I use a Weston Master III that is about 60 years old, but I check it regularly against my LunaSix (European version of the LunaPro, it was recalibrated by Gossen right after I got it) which I use for lowlight. I also have a NIB Master III for just in case. :wink:
    The trouble is, the old meters when they go bad don't just stop working, they get progressively less sensitive and you can go on using them for a while - until you put a roll of E-6 in the camera and it comes back with featureless highlights. B&W and C-41 films will tolerate the overexposure, at least to a point.
     
    Last edited by a moderator: May 16, 2014
  15. Jim Noel

    Jim Noel Member

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    I hope you are not keeping the NIB Weston in the box at all times. Selenium cells need to be activated to keep them in good condition. Open it up and expose it to ambient light for a few hours at least one day each month to keep it in best condition.
     
  16. E. von Hoegh

    E. von Hoegh Member

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    Really? I never heard that.
    I bet it hasn't been out of the box in at least ten years. Schroedinger's meter...:blink: