Tobias densitometer instructions

Discussion in 'B&W: Film, Paper, Chemistry' started by dario, Nov 22, 2007.

  1. dario

    dario Member

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    Hi folks - I've just acquired a Tobias densitometer, model TRX-UG, but no instructions. Does anyone have an instruction manual, please? Thanks.
     
  2. dancqu

    dancqu Member

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    I've a Tobias TB+ with all. Likely no help. I think
    they are still in business. Dan
     
  3. dario

    dario Member

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    Hi Dan - Thanks for the reply. I emailed the company but have had no reply.

    But I wonder if your instrument is sufficiently similar to mine that you can help me.

    My instrument has two toggle switches. One is labelled 'auto xmit' / 'xmit' and the other is labelled 'density, half tone, null' / 'zero, base, solid'. I don't know what these mean and operating them seems to make no difference to the reading I get.

    I've used a Kodak calibrated stepwedge and adjusted the 'cal' and 'zero' adjustment screws so that when I take readings with no film and with the maximum density step, the display reads zero and 3.11 (which is what it should be). That seems OK, but when I take a reading with the minimum density step, I get 0.15, when it should be 0.05. So I'm a bit mystified.

    Can you offer any advice please?
     
  4. ath

    ath Member

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    I guess, the first step is 0.05 over base fog. Did you zero the densitometer on the base fog?
     
  5. dario

    dario Member

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    Hi Andreas - Thanks for you interest.

    I zeroed the densitometer with no film. The first step in my wedge is clear film and has a measured (by Kodak) density of 0.05, so that is film base + fog. The next step is 0.19 and is the first area of visible density. The next step is 0.35 and so on.

    If I zero on the first step, then the second step reads 0.14, and the third step reads 0.30, which are consistent with the first step being 0.05. So it doesn't make sense to zero on no-film and get a fist step reading of 0.15. I'm baffled. Unless I'm using the densitometer incorrectly....
     
  6. dancqu

    dancqu Member

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    [QUOTES=dario;552401]
    "Hi Dan - Thanks for the reply.
    I e-mailed the company but have had no reply."

    I can do only a little better than none. I turn my TB+ on,
    zero, then take readings. A one toggle B&W transmission
    unit; up for zero, fog, and solid; down for density,
    halftone -, and halftone +.

    "But I wonder if your instrument is sufficiently similar to mine
    that you can help me."

    Yours is of the series TRX. There is also a TRX-W. No word in
    my brochure of the UG. All three are I'd say Color reflection/
    transmission densitometers. They derive from the TRI and
    you should have a plug-in reflection probe with flex cable.
    Got that? I'll give my instruction manual a study and get
    back to you. Made any progress?

    "... but when I take a reading with the minimum density step,
    I get 0.15, when it should be 0.05. So I'm a bit mystified."

    "Can you offer any advice please?"

    A real mystery. Contact by PM. Dan
     
  7. dario

    dario Member

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    Hi Dan - Thanks for your reply. Sorry, but I've been out of touch for a week or so.

    I do have the reflection plug-in, but haven't tried it yet. I wanted to get the transmission sorted first.

    I did a couple of runs measuring my calibrated stepwedge. I got quite consistent results between the two runs, but an apparenly random (RMS) error of about 0.018 density units. The error is more or less constant over the whole range, but has a slight non-linearity, which is not a problem.

    I haven't figured why i get inconsistent results if I zero on no film, but I seem to have a workable machine, which is the important thing.

    Thanks for your interest.