Pentax Spotmeter V Low Light indicator affect reading

Discussion in 'Large Format' started by cyrus_beh, May 5, 2012.

  1. Hi everyone,
    I have a Pentax Spotmeter V, and I noticed that when I meter extremely dim areas (EV 1-3), the needle moves up by two-thirds of a stop when I push the indicator lamp button. Which reading should I believe - the one with or without the indicator light on? Is this a sign of a light leakage that should not exist?
     
  2. Cyrus, I don't know what the answer is, but I have the same problem with mine. I simply don't use it with the illuminator on.
     
  3. The problem is most likely due to the fact that the meter was designed to use mercury batteries. I have spent the last hour web searching and cannot find the current rating for the manual listed PX13 battery, just that it had a stable 1.35v regardless of load.
    The incandescent lamps of that era are high current compared to newer technology lamps. Having the lamp replaced with a LED might correct the problem.
    http://www.buhla.de/Foto/batt-adapt-US.pdf
    Reports say the Spotmeter V has a built in voltage bridge so the varying output of an alkaline battery or the higher voltage of a silver oxide will not affect its readings. If I had one in my possession I would make a adapter that would allow me to measure battery voltage and total meter current at the battery at the same time and test the meter in a variety of conditions.
     
  4. These meters are getting pretty old at this point (I've had mine for 25 years at least). I was just going to suggest that some light baffel or seal had broken down and was letting light from the low light assist bulb or diode get where it shouldn't.
     
  5. The Pentax V was not designed to use mercury batteries. I own one and still have the owners manual. I agree with Robert it may be time for service. Mine doesn't move when the light button is pushed.
    Google Richard Ritter for repairs.
     

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