RH Designs Zonemaster II/Densitometer mode

Discussion in 'Darkroom Equipment' started by jstraw, Dec 8, 2006.

  1. jstraw

    jstraw Member

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    Questions for ZII users:

    When using the meter as a densitometer do you use the enlarger head as the light source?

    Do you meter through the negative directly or meter the projected image?

    If I project a Fb+F sheet and LOG d0.00 for that, will I get actual densities when metering other test sheets or some diluted value due to projection?
     
  2. Matthew Gorringe

    Matthew Gorringe Member

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    I measure the projected image, use the rebate of each image for Fb+F and then it gives you relative densities to your first reading. I hope this is right but I can't answer your last question. Personally I can't see why the density readings would be diluted.
     
  3. ath

    ath Member

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    Yes, the values are different from the "standard" densitiy values. Common measurement of density is with diffuse light.
    With the Zonemaster you are measuring the projected density, which is dependent on the type of light source. The density with a condensor head will be higher than with a cold head or the values with a proper densitometer (this is the callier effect).
    However, if you want to match the density of your negative to your paper this is exactly what you want to have. Just remember that this value is only valid for this enlarger.

    HTH,
    Andreas
     
  4. jstraw

    jstraw Member

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    So, for a film speed or development time tests, I'm imagining projecting an 8X10 (or whatever) image of a Fb+F test sheet and zeroing my reading. Then, replacing it with a series of test sheets and measuring to find a density reading of X, and when I've found my desired X, I have a result for that film/development time for that specific enlarger/lens/height/aperture/stabilized-light-intensity combination.

    Is that about right? Or will a reading of say .9 over Fb+F done this way have no real relationship to a reading of .9 on a transmission densitometer?
     
  5. ath

    ath Member

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    Yes, you are right. What you are doing is measuring the light ratios for negative parts with different densities. If you want to calibrate your negative/positive process, this is what you need. It's the light that exposes your paper, not the density.
    However, the light ratio depends on the film density AND the type of light source.
    To become independent of the type of light source densitometers use diffused light.

    And because of this, no, your value will not be the same as a value measured with a densitometer and not the same as the curves shown in the datasheets.
    Depending on your light source, it may be close.
     
  6. jstraw

    jstraw Member

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    Thanks.
     
  7. RJS

    RJS Member

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    RH as densitometer


    I've tried using mine and it just doesn't seem to work properly - Richard at RH has tried to help but no. I have a Stouffer calibrated step wedge I project and, using the .04 density as my baseline I get readings which just don't correlate with the Stouffer densities. Some are quite close and others are off by a very wide margin in no preidictable direction. This makes no sense because the exposure recommendations, using the same meter, are very close to perfect, just about every time!