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Thread: Why calibrate densitometer?

  1. #1
    Hack Pawlowski6132's Avatar
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    Sep 2009
    Detroit - Come Visit

    Why calibrate densitometer?

    If I'm just determining my PEI, does my densitometer need to be calibrated? I'm just looking for a relative difference of .10 between base-plus-fog and Z1 right? If my densitometer is off both measuresments will be off by that same amount but I can stiill calculate the difference right?

  2. #2
    Big Negs Rock!
    Join Date
    Mar 2000

    Re: Why calibrate densitometer?

    Interesting. I do calibrate my densitometer with calibrated piece of film for the high end and just set it to zero when there is no film. The low end is simple.
    Mark Woods

    Large Format B&W
    Cinematography Mentor at the American Film Institute
    Past President of the Pasadena Society of Artists
    Director of Photography
    Pasadena, CA

  3. #3
    ic-racer's Avatar
    Join Date
    Feb 2007

    Re: Why calibrate densitometer?

    If you don't have a calibration standard, then I'd pick a piece of well processed film with a density around 1.8 and check that periodically to make sure the densitometer does not drift with time.

    I agree, it would have to be way, out of alignment to mess up the 0.1 measurement.

  4. #4

    Join Date
    May 2009

    Re: Why calibrate densitometer?

    correct, you are looking for the difference betwen base+fog and zone1 value. Providing the base+fog value is reasonable then there should be no need to calibrate even if in reality it is out by a little bit. Only if you have unexpected base+fog might you think about a calibration check but it could be you do have high (or low) base+fog.

  5. #5
    Lachlan 717
    Join Date
    Apr 2007

    Re: Why calibrate densitometer?

    Simple enough to calibrate even if you don't have specific "factory" calibration stock.

    Just fine a base + fog piece of film, run a density measure on it, record the outcome and then put it away in a dark and dry place for any future recalibration.

    Any difference in its indicated density over time will show as a difference to this intial reading.

    But, as far as I know, use of relative difference is the important thing.


  6. #6
    Hack Pawlowski6132's Avatar
    Join Date
    Sep 2009
    Detroit - Come Visit

    Re: Why calibrate densitometer?

    Thanx folks.

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