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Thread: Densitometer reading upside-down?

  1. #1

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    Densitometer reading upside-down?

    I have a Konica "nice print system" densitometer I bought on eBay. It was reading ok for a while, but it was a little off (compared to a calibrated step wedge.) I noticed that there was some dust in the reading area, so I blew it out with some dust-off. Now I get strange readings... 2 minus the reading gives me the correct reading. It also has a minus sign in front , but I'm not sure if it was there before.

    For instance I read
    -1.96 for a wedge that's calibrated valuel is .04
    -1.83 = .17
    -1.67 = .33
    etc.

    Does anyone know this densitometer? I guess I could use it like this, but it's a pain.

  2. #2

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    Re: Densitometer reading upside-down?

    I don't know about your meter - maybe you could post a photo of it as several different meters have been rebranded, like Noritsus and X-rites I've seen.

    Anyway, it looks like your meter was rezeroed somehow and it now has a zero that is negative. So everytime you take a reading of something, which has a positive density value, you get the density number added to the negative number. I hope that made sense. i.e.
    (-1.96 + 0.33 = -1.67)

    I suggest that you rezero it and see if that helps.

  3. #3

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    Re: Densitometer reading upside-down?

    When the offset of the amplifier is misadjusted, you will get negative readings. So adjust the densitometer properly.

    Peter K

  4. #4

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    Re: Densitometer reading upside-down?

    In the very unlikely event that you don't already know how to do this: with no film in place take a reading and adjust the zero calibration to zero. No calibration targets are required for setting zero. Then you can use your wedge to calibrate the span (ie the higher end of the density range).

    Best,
    Helen

  5. #5

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    Re: Densitometer reading upside-down?

    I do know that. I was trying to get it to work, and discovered that if I zeroed it out on the first step of the step wedge, then I get correct readings, but offset by the density of the first step. If I...

    zero it out on the .04 wedge
    then the second wedge is .13 (.17 - .04)
    the third one is .29 (.33 - .04)

    but if I zero it out with no film in the reader, I get the negative numbers.

    Strange.

  6. #6

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    Re: Densitometer reading upside-down?

    Very strange. I Googled 'konica nice print system densitometer' and found this thread which mentions its similarity to an XRite 320.

    The negative readings imply that the receptor is getting more light back than when it was zeroed, and one way for that to happen would be if a reflection head was zeroed with nothing in place. That seems partially consistent with some of your observations, but not all. Of course you can't zero a reflection densitometer.

    If you zero it with the 0.04 step in position, what reading do you get with nothing in position?

    Best,
    Helen

  7. #7

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    Re: Densitometer reading upside-down?

    Good question. I'll try that tonight...

  8. #8

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    Re: Densitometer reading upside-down?

    There is something wrong with the electronic, possible a broken OP-amplifier. Heat up your soldering iron.

    Peter K

  9. #9

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    Re: Densitometer reading upside-down?

    When I zero it on the .04 strip, then reading nothing returns -1.96

  10. #10

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    Re: Densitometer reading upside-down?

    I am beginning to wonder if this densitometer reads both transmission and reflection.
    If so, it may be set for reflective while attempting to read transmission.
    Also, it is possible to zero a reflection densitometer with the correct calibration tablet.

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