Using a color analyzer as a densitometer?

Discussion in 'Darkroom Equipment' started by Anupam Basu, Jan 28, 2006.

  1. Anupam Basu

    Anupam Basu Member

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    Hello, I am trying to use a Beselar PM2L analyzer as a densitometer to do BW film tests. I am hoping this will allow me to do more rigorous tests than the rough print tests I have done thus far. Am I right in assuming this can be done? I have no exprience with a color analyzer, so might be completely off the ball here.

    I am setting it to the "white" channel and taking readings from various frames of 35mm film, reading the upper scale denoting filtration because the tim scale is not linear. Any particular tips and advice you might have would be helpful. I am an absolute beginner at this, so please explain the details as simply as possible.

    many thanks,
    -Anupam
     
  2. Nick Zentena

    Nick Zentena Member

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    The only way I can see this working is if you get a step wedge to calibrate the process.

    The colourstar 3000 etc are designed to handle the densitometer function but I don't think the Beselers ever were.
     
  3. Anupam Basu

    Anupam Basu Member

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    Thanks. I'll get a step wedge to compare. But I am wondering if it might be possible to use this setup as described in this photo.net thread using a blank frame as a comparative starting point.
     
  4. donbga

    donbga Member

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    I've used the PM2L for a densitometer but it only works up to a point. Ne sure to NULL the meter using your lightsource. I simply adjusted the analyzer on the white channel so that the meter needle was deflected all the way to your left on the "0" mark. The density range was about 2.0 log density if I recall correctly.

    You can verify your readings by measuring a calibrated step wedge or by measuring neutral density filters. I did both and had fairly good results. As long as you can see where to position the area of the negative over the light receptor aperture you should be okay. Negatives areas of high density are difficult to align to the aperture.


    Don Bryant
     
  5. Tom1956

    Tom1956 Inactive

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    Thread marked. There's not much on this in the Google searches. I would like answers on it also, all this time later. Thank you.
     
  6. ac12

    ac12 Member

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    I've used a Besler analyzer as a desitometer before.
    But I think it was a PM4, the meter display was such that I could easily read the density right off the meter, by zeroing on a bright part of the negative then reading the darkest part.

    BTW I also used a Unicolor exposure meter for this purpose. The battery powered meter is a lot more portable.
    But then color analyzers are so cheap that you can get one to play with and try. Just have to make sure that it works, and that the detector tube hasn't been damaged. I do not have a manual, but I recall that the tube could be damaged by exposure to too much light...ie sunlight.
     
  7. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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  8. ic-racer

    ic-racer Member

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    Yes, you can use your enlarger as a light source and place the test negatives right over the probe orifice to get relative density.
    You can use either scale. The bottom scale is in stops, the upper scale is logD x 100. So 30 on the upper scale = 0.3 logD to use for your H&D curves. You can twist the knobs and or adjust the enlarger aperture to zero the scale to your negative base. H&D curves are educational and fun to make.
    Using the probe to get negative range when printing is also of practical value. Section VIII in the manual shows a clever way to use two of the channels to help match an unknown negative to a known negative, in order to decrease the number of test exposures one might need. The manual details how to set up one channel to measure contrast range and another for absolute exposure.

    A calibrated step wedge is not needed unless you suspect the meter is out of calibration. Unless you know how to adjust the slope of the response on that unit (I don't), I'd just go with readings relative to your film base.
     
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