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Re: [Digital BW] Re: Invalid linearize curve -- not constantly increasing

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  • Ernst Dinkla
    ... It is not that different with an X-Rite Eye 1 Pro. I count to three on each patch before lifting it. I also think that one should try to keep gloss paper
    Message 1 of 11 , Jun 1, 2012
      On 06/01/2012 02:31 AM, Paul wrote:
      > What I have to watch with my DataColor unit is my lifting the meter too
      > soon. The way I know I've done this is that the color values (Lab A and
      > B) will spike in one direction or the other -- way off the trend line. I
      > see this when I'm looking at the graphs in Excel. What I do to correct
      > the problem is simply go back and remeasure the patch correctly. I
      > simply write the new, correct values into the Excel boxes and save the file.
      >
      > Paul
      > www.PaulRoark.com


      It is not that different with an X-Rite Eye 1 Pro. I count to three on
      each patch before lifting it. I also think that one should try to keep
      gloss paper patches as flat as possible under the spectrometer, the
      geometry of the spectrometer optics is not an ideal Ulbricht sphere but
      a practical compromise that works very nice with matte papers but less
      so with high gloss papers. Targets printed and dried fast with a hair
      dryer and then placed on more sheets of the same paper for measuring
      should be pressed firmly with the meter to get that patch flat.

      There is another way to get the Lab b on a zigzag course. Measure a
      target with heavy bronzing and the 45/0 degree reflection optics in a
      spectrometer are affected by the bronzing layers. The measured color is
      not 1:1 to what the eye sees in color of the bronzing but that is
      understandable given the spectrocam's light source and sensor as another
      light + another observer. In practice one would not select a B&W
      paper/ink combination that creates that much bronzing but in color
      printing it may be less obvious and play a role when colors are off
      after profiling. Grey range in color prints for example. I will put some
      QTR linearisation plots on my site to show the difference between a
      target with and without bronzing.


      --
      Met vriendelijke groet, Ernst

      Dinkla Grafische Techniek
      Quad, piëzografie, giclée
      www.pigment-print.com
    • wolverinemsu
      I only remove those that are way out of whack . Since I use the 51-patch random test file, it becomes very clear when a point isn t even close to the model
      Message 2 of 11 , Jun 1, 2012
        I only remove those that are "way out of whack". Since I use the 51-patch random test file, it becomes very clear when a point isn't even close to the model curve in Excel. I use the strip mode in ColorMunki to read the patches, and sometimes I get an anomoly.

        After reading some of the other posts in this thread, I have to admit that I'm sometimes not real careful about making sure the sheet is completely flat, that the Munki exactly follows the centerline of the patches, or doesn't tilt a little during the scan. I've also found that the speed at which the Munki is moved over the patches can have an effect on the final output; too slow and it sometimes misses a patch completely. I'm getting better at it, and will pay more attention to these things.
      • Terry Ritz
        ... Not that s very interesting, and something well worth keeping in mind. Would L* values suffer in this circumstance? Terry.
        Message 3 of 11 , Jun 1, 2012
          On 12-06-01 1:33 AM, "Ernst Dinkla" <e.dinkla@...> wrote:

          > There is another way to get the Lab b on a zigzag course. Measure a
          > target with heavy bronzing and the 45/0 degree reflection optics in a
          > spectrometer are affected by the bronzing layers. The measured color is
          > not 1:1 to what the eye sees in color of the bronzing but that is
          > understandable given the spectrocam's light source and sensor as another
          > light + another observer. In practice one would not select a B&W
          > paper/ink combination that creates that much bronzing but in color
          > printing it may be less obvious and play a role when colors are off
          > after profiling. Grey range in color prints for example. I will put some
          > QTR linearisation plots on my site to show the difference between a
          > target with and without bronzing.

          Not that's very interesting, and something well worth keeping in mind.

          Would L* values suffer in this circumstance?

          Terry.
        • Ernst Dinkla
          ... Hardly I think. The 21 B&W step range is as good as the one that has no bronzing. Same paper, different inkset. -- Met vriendelijke groet, Ernst Dinkla
          Message 4 of 11 , Jun 1, 2012
            On 06/01/2012 04:32 PM, Terry Ritz wrote:
            > On 12-06-01 1:33 AM, "Ernst Dinkla" <e.dinkla@...
            > <mailto:e.dinkla%40onsneteindhoven.nl>> wrote:
            >
            > > There is another way to get the Lab b on a zigzag course. Measure a
            > > target with heavy bronzing and the 45/0 degree reflection optics in a
            > > spectrometer are affected by the bronzing layers. The measured color is
            > > not 1:1 to what the eye sees in color of the bronzing but that is
            > > understandable given the spectrocam's light source and sensor as another
            > > light + another observer. In practice one would not select a B&W
            > > paper/ink combination that creates that much bronzing but in color
            > > printing it may be less obvious and play a role when colors are off
            > > after profiling. Grey range in color prints for example. I will put some
            > > QTR linearisation plots on my site to show the difference between a
            > > target with and without bronzing.
            >
            > Not that's very interesting, and something well worth keeping in mind.
            >
            > Would L* values suffer in this circumstance?
            >
            > Terry.


            Hardly I think. The 21 B&W step range is as good as the one that has no
            bronzing. Same paper, different inkset.


            --
            Met vriendelijke groet, Ernst

            Dinkla Grafische Techniek
            Quad, piëzografie, giclée
            www.pigment-print.com
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