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  1. #1
    david m. baker is offline Junior Member
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    Question l.a.b. values for Pantone colors

    Good afternoon:

    Per the subject, is there a "calculator" tool out there for converting spot/Pantone colors to their l.a.b. values? I have to find l.a.b. values for the following PMS colors:

    5483
    417
    452
    5507

    I know you can pick this up in Photoshop, but I also understand the values may shift depending on what your default color space is?

    Bottom line what I need to do is create reference data in my spectro in order to capture deltaE variance on these four mission-critical colors. Any suggestions are welcome!

    Cheers,
    -d-

  2. #2
    meddington's Avatar
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    Quote Originally Posted by david m. baker View Post
    I know you can pick this up in Photoshop, but I also understand the values may shift depending on what your default color space is?
    Its not really the Pantone provided Lab values that are shifting, but these Lab values may or may not be achievable depending on the destination color space. As it should be really, as Pantone is first and foremost an ink formulation guide. Different substrates and print conditions using the same ink formulation result in different visual results (i.e different CIELab values).

    IMO, creating a CIELab reference for spot colors is usually best done up front with ink drawdowns on the actual substrate provided by the printer and approved by the client.

  3. #3
    aricker is offline Junior Member
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    There's a few threads on this subject already, if memory serves, and the consensus was that Photoshop values are probably all you have to go by. Pantone doesn't give digital values easily.

  4. #4
    david m. baker is offline Junior Member
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    Quote Originally Posted by meddington View Post
    IMO, creating a CIELab reference for spot colors is usually best done up front with ink drawdowns on the actual substrate provided by the printer and approved by the client.
    EXACTLY! Your suggestion is, ultimately, what I've landed on as the best solution. After a little RTFM time, I figured out how you can create a reference based on the ink on substrate (which, thankfully, I have samples of).

    Thanks!
    -d-

  5. #5
    gordo's Avatar
    gordo is offline Senior Member
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    Quote Originally Posted by david m. baker View Post
    I have to find l.a.b. values for the following PMS colors:

    5483
    417
    452
    5507

    Bottom line what I need to do is create reference data in my spectro in order to capture deltaE variance on these four mission-critical colors. Any suggestions are welcome!
    Pantone certified RIPs have Pantone's defined CIE L*a*b* values included to aid in the conversion of spot into process.
    Here are Pantone's values for the colors you requested:

    PANTONE 5483 C 55.09 -18.65 -11.81
    PANTONE 417 C 46.86 -1.9 5.77
    PANTONE 452 C 72.12 -2.74 16.72
    PANTONE 5507 C 73.7 -5.27 -1.98

    Pantone does not provide these Lab values as a target for mixing up their inks, instead they use recipe formulas as per their swatch books. I can't guarantee the Lab values are the most up-to-date since Pantone does change them from time to time and not all RIPs are up to date. But they should give some guidance.

    best, gordo

  6. #6
    Bondi_dan Guest

    Default l.a.b. values for Pantone colors

    Hi Gordo,

    XRite have in fact published Lab values for Pantone colours.

    If you have an iPhone get the myPANTONE app.

    There you can search for Pantone colours and get their Lab* values.

    BTW 5483 C showed up at L* 52.14 a* -17.65 b* -10.82.

    This means you and I have a Delta E of 3.27 !

    Regards,

    Dan

  7. #7
    gordo's Avatar
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    Quote Originally Posted by Bondi_dan View Post
    BTW 5483 C showed up at L* 52.14 a* -17.65 b* -10.82.

    This means you and I have a Delta E of 3.27 !

    Regards,

    Dan
    Thanks for the app info.

    As I wrote, Pantone does change their Lab values from time to time so I couldn't promise that the numbers I gave were the latest.

    Regarding the Delta E of 3.27. You're using CIE 1976 to calculate the color difference. If I'm not mistaken, the standard for measuring color difference with spot colors is CMC (2:1). That makes the Delta E only 1.57.

    best, gordo

  8. #8
    Bondi_dan Guest

    Default l.a.b. values for Pantone colors

    Hi Gordo,

    Quote:
    Regarding the Delta E of 3.27. You're using CIE 1976 to calculate the color difference. If I'm not mistaken, the standard for measuring color difference with spot colors is CMC (2:1). That makes the Delta E only 1.57.
    End Quote.

    I know the good guys at XRite with the Ink Formulation Software love to use CMC (2:1) because it give the lowest number but Delta E 76 or Delta E (ab) as it is also called is the mainstream in ISO Standards and print buyers in Europe. I see no reason to treat spot colour differently.

    In the ISO world there is currently a move towards "Delta E 00".

    Regards,

    Dan

  9. #9
    gordo's Avatar
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    Quote Originally Posted by Bondi_dan View Post
    I know the good guys at XRite with the Ink Formulation Software love to use CMC (2:1) because it give the lowest number but Delta E 76 or Delta E (ab) as it is also called is the mainstream in ISO Standards and print buyers in Europe. I see no reason to treat spot colour differently.
    Actually, the use of CMC 2:1 for spot colors that I referred to comes from FIRST (Flexographic Image Reproduction Specifications & Tolerances published by the FTA). A lot of spot colors are used in Flexo printing which is perhaps why they write about it in their specifications.

    Now I'm probably not up to date, but my copy of ISO 12647-2 does not state anywhere that I could find which formula should be used to calculate Delta E. Nor does my copy of GRACoL 7 which is based on ISO 12647-2. And neither of them talk about tolerancing for spot/line colors. (See latest RE:Print about standards: http://media.printplanet.com/images/...ds-Meeting.png) DeltaEs are mentioned in the documents - but not how they required to be calculated.

    So, I think that Delta E 76 might be popular in common usage, but I don't think that it is in the specifications as the required method either for process or spot colors. So, AFAIK, vendors and printers are free to calculate DeltaE anyway they choose (to get the results that they are trying to prove :-p) One hopes that they say how they're doing the calculation, however, in my experience, this is rarely done. I.e. Vendor could use CMC 2:1 to calculate color difference and states "It's a DeltaE on only 1.5" while the customer is thinking that Delta E 76 was used and as a results says "Fantastic! I'll buy it."

    Like I said, I'm probably wrong - so please correct me by quoting from the specifications on how to tolerance process and spot colors.

    best, gordo
    Last edited by gordo; 12-16-2011 at 01:22 PM.

  10. #10
    chevalier's Avatar
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    Graphics - PANTONE PLUS Digital Libraries for Adobe

    These free swatch libraries for Adobe software from Pantone are all based on LAB values. They replace the old legacy ones.


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