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About ISO reference Hue Angles (LcH)

  • 1.  About ISO reference Hue Angles (LcH)

    Posted 03-12-2019 08:37 PM
    Hue angles play a very important part in print analysis and diagnosis but I haven't seen in the GRACoL 2013 reference data, Hue Angle of the reference Paper sustrate.
    I have following questions:
    a. What are the reference LcH values for the paper substrate, not Lab but LcH
    b. Also the reference LcH values of C,M,Y and K ISO inks (Offset)
    c. Lastly the tolerance values will be greatly appreciated as well

    Everywhere I find Lab reference values but difficult to find the LcH

    Hope somebody can help

    Thanks
    Edward

    ------------------------------
    Edward Duwariti
    Nationwide Training and Compunet Services SA de CV
    Mexico D.F.
    +525552028047
    ------------------------------


  • 2.  RE: About ISO reference Hue Angles (LcH)

    Posted 03-13-2019 02:17 AM
    Hi Edward,

    I think the reason we don't provide Chroma and Hue values is simply a lack of demand and a desire not to bombard users with too much information.  OK, that's two reasons.

    CIELCH values can be calculated easily from CUELAB, if you need them.
    There's a Microsoft Excel workbook on my website with many such useful formulae. Go to www.HutchColor.com and search under the FREE button. Guess how much it costs.

    Perhaps this should be discussed at the next Print Properties meeting. Maybe it's time to add more values.

    Don Hutcheson
    908-500-0341
    (Typos courtesy of iPhone's teeny-tiny keyboard and not-so tiny thumbs)





  • 3.  RE: About ISO reference Hue Angles (LcH)

    Posted 03-14-2019 05:02 PM
    Hi Don
    Thanks very much for your answer. I got to play with the Excel file and it's pretty cool what you have done. It answered my questions and more.
    You are right giving us more information is better because LcH really answers other questions of what happens when substrates and inks with different Hue angles are used within the same run.

    Many thanks and keep it up

    Regards
    Edward

    ------------------------------
    Edward Duwariti
    Nationwide Training and Compunet Services SA de CV
    Mexico D.F.
    +525552028047
    ------------------------------



  • 4.  RE: About ISO reference Hue Angles (LcH)

    Posted 03-15-2019 08:23 AM
    A very similar topic is on the PPC agenda in Vancouver

    Ron

    ------------------------------
    Ron Ellis
    Owner
    Ron Ellis Consulting LLC
    Stratham NH
    (603) 498-4553
    ------------------------------



  • 5.  RE: About ISO reference Hue Angles (LcH)

    Posted 03-13-2019 02:29 AM
    CUELAB is not a new color space! It's a free typo generated randomly by my uPhone.

    Don Hutcheson
    908-500-0341
    (Typos courtesy of iPhone's teeny-tiny keyboard and not-so tiny thumbs)

    On Mar 13, 2019, at 07:17, Don Hutcheson <don@...> wrote:

    Hi Edward,

    I think the reason we don't provide Chroma and Hue values is simply a lack of demand and a desire not to bombard users with too much information.  OK, that's two reasons.

    CIELCH values can be calculated easily from CUELAB, if you need them.
    There's a Microsoft Excel workbook on my website with many such useful formulae. Go to www.HutchColor.com and search under the FREE button. Guess how much it costs.

    Perhaps this should be discussed at the next Print Properties meeting. Maybe it's time to add more values.

    Don Hutcheson
    908-500-0341
    (Typos courtesy of iPhone's teeny-tiny keyboard and not-so tiny thumbs)





  • 6.  RE: About ISO reference Hue Angles (LcH)

    Posted 03-13-2019 10:03 AM
    LCH is a different way of expressing L*a*b*. Mathematically, it's a conversion of the cartesian coordinates of a*b* into the polar coordinates of C*h°. You can find excellent resources for color math at http://www.brucelindbloom.com.

    Regards,
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