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  1. #1
    slehning is offline Member
    Join Date
    Oct 2007
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    52

    Default G7 Grey Balance numbers

    We are a small label printer attempting to standardize color in our plant. We do not have any of the proofing devices and or certification software i.e; Epson with inline spectros or Oris Certified proof software to drive the devices to verify our proofs automatically.

    We do have an indigo WS6000 and Esko color engine software so I can manipulate color and at least drive the color on the Indigo. I want to create a G7 standard on our Indigo for creating proof to press matches and make the Indigo our stake in the ground for the press. Once I am able to achieve a provability stake in the ground with this device, we can move to the press room. As I say, I do not have any verification tools other than reading the 50, 40, 40 grey patch I have created and reading it with our i1 spectra scan. I have created a test and read the LAB of my grey.

    The Substrate LAB is L:95 a: -0.39 b: 0.35 ( This will change depending on the stock the job calls for however )

    My 50, 40, 40, Grey value after calibration is L: 57.38 a: -0.85 b: 0.11. I guess my question is, based on the G7 standard, what is my optimum target for LAB that I am looking to hit. I am hoping in theory, if I can profile the Indigo based on G7 and the press operator does their part of doing a calibration on every stock they run, we should be able to maintain a Delta E range of acceptability from substrate to substrate.

    Or am I out to lunch in thinking this is achievable with little tools to work with or at all.

    Thanks In Advance for the help

  2. #2
    Stephen Marsh is offline Senior Member
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    Default

    G7 is the method to arrive at grey balance. What is your grey balance target, GRACoL C1?

    For a free (with an option to pay for more features) ISO CMYK quality assurance tool, there is the following from UGRA:

    http://www.ugra.ch/uppct.phtml

    The UPPCT tool does not support the i1 spectra scan, just the standard hand held i1. It is also using the F39/ISO Coated v2 data as a reference, not GRACoL C1 which is slightly different.

    If you have i1 profiler software, it has a colour quality confirmation option for measuring Fogra or IDEAlliance media wedges/colour bars for GRACoL.

    With some spreadsheet skills, I am sure that somebody could cook up their own basic/simple ISO or GRACoL colour confirmation software. The Fogra or GRACoL target values are known, the simple dE76 formula can be programmed into Excel...all that one has to do is get the actual measurements populated into the correct cells, which could probably be semi-automated as well (as it would be no fun manually entering in 72 sets of L*a*b* values for a Fogra wedge). Of course, for your own internal colour bar and quality checks, you could create your own media wedge with a lesser amount of patches (primary, secondary overprints, grays etc).


    Stephen Marsh
    Last edited by Stephen Marsh; 10-18-2012 at 03:04 PM.

  3. #3
    tmiller_iluvprinting's Avatar
    tmiller_iluvprinting is offline Senior Member
    Join Date
    Oct 2007
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    303

    Default

    You can download the Substrate Relativity Calculator from the IDEAlliance website, this should help.
    Regards,
    Todd


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