Light Meter Problems

Discussion in 'Medium Format' started by simon_taylor, Oct 31, 1997.

  1. Hello

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    I Have recently purchased a Sekonic L408 light meter. I am getting inconsistent results using incident metering with slide film, in daylight pointing the meter directly at the camera (Mamiya RB67)the transparencies are too dark.

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    Any assistance would be greatly appreciated.
    Thanks
     
  2. I have used a Sekonic L408 for the better part of the last year. I found that with transparency film in incident mode I got the best results by setting the ISO one setting less than the rating of the film, and sometimes even two.

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    I am assuming of course, that you are twisting the lumisphere out of it's recessed position.

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    I hope this helps.

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    Don
     
  3. Don, I have the same problem and discovered that my 408 underexposes by about 2 stops when
    shooting slide film. When I used a Kodak gray card tilted at approximately the correct angle
    (according to the instructions) and my Rollei's spot meter, it reads about 2.5 stops over the
    sekonic's incident light reading. My Rollei's meter gives proper exposure. It's because of
    this reason that I seldom use the meter. I checked the calibration (compensation set to zero) vs. a Minolta meter and my 408 read 1/2 stop over the minolta's reading. The only remedy I can think of is to compensate the meter by two stops, or by one stop and bracketing
    from the camera's reading down to the meter's reading. The problem is that I'm not abosolutely certain that the difference is always two stops. Sometimes it looks like 1 stop,
    sometimes two. All my usage is under overcast skies.
     
  4. I find that if you think readings are suspect, you can cross-check/calibrate by using the integral "spot"meter and a grey card to compare with the incident reading. In cases of extreme scepticism, I sometimes also cross-check the grey card reading with my camera's TTL meter. If still in doubt, bracket!

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    Mark.

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    --
    Mark A. Brown
    Control Systems Division
    National Aerospace Laboratory
    7-44-1 Jindaijihigashi-machi, Chofu, Tokyo 182
     
  5. A very simple, quick check to see if an incident meter is out of calibration is to cross check it using the good old "Sunny 16 Rule". Simply set the shutter speed on the meter close to the ASA number of the film your using, aim the meter at the sun (on a CLEAR day) and you should get a reading close to f16. For Example, say your using ASA 64 film. Set the ASA on the meter to 64, the shutter speed to 1/60 and take a reading of the sun. You should be getting a reading of f16 give or take a 1/3 stop. If it's way off, meters can be calibrated. Another thing to remember is that just because a film box says ASA 100, doesn't mean it actually is. All of the transparency film that I shoot, I rate between 1/3 to 1 full stop over what the manufacturer says it is. Also, are you sure it's not a camera problem.

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    Good Luck
     

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