Discussion: View Thread

G7 with Light Fast Inks

  • 1.  G7 with Light Fast Inks

    Posted 15 days ago
    Hello, I'm looking for some advice on doing a G7 calibration with lightfast inks to match a Gracol 2013 proof (If that's even possible). I am using Curve 4 and have good Solid CMYKRGB lab values after the linear calibration run.

    After the linear calibration run I applied the curves and made new plates and the result was I had a very warm neutral grey curve. I did another iteration which resulted in better neutrals 50% and below but above 50% it was still warm. I ended up going back to the 1st iteration and did some manual curve adjustments to get a usable result, but it still wasn't what I consider a close match to Gracol 2013. I noticed if I get a decent grey curve I sacrifice color in flesh tones, tans, and browns.

    Thanks,
    Greg

    ------------------------------
    Greg Sterwald G7 Professional
    Prepress Manager
    Crossmark Graphics Inc.
    New Berlin WI
    (262) 909-1588
    ------------------------------


  • 2.  RE: G7 with Light Fast Inks

    Posted 15 days ago
    Greg,

    Did you confirm that the that curve you applied passed G7?

    More than likely you will not pass at G7 targeted to Gracol 2013, but you should have a good "shared visual appearance" as long as the curve is good.  The inks are going to print too muddied and dark.  It is strange that your linear plates had a good solid CMYKRGB...Was this confirmed with a handheld spectro at the press?  The G7 Curves generated in Curve 4 should not effect the solids.  I would first confirm the press conditions and settings are the same from run-to-run before anything.

    -Joey Nutis

    ------------------------------
    Joey Nutis G7 Expert
    Print Production Manager
    Nutis Press, Inc.
    Columbus OH
    (800) 848-6266
    ------------------------------



  • 3.  RE: G7 with Light Fast Inks

    Posted 14 days ago
    Hi,
    You write that you have valid solids in CMYKRGB.
    But what is the neutrality of 300% CMY. Is the value of a* and b* by any chance far from neutral (a* 0, b* 0)?
    You then have to focus on improving the neutrality of the 300% CMY - maybe changing the order of the inks.

    ------------------------------
    Wojciech Bialkowski G7 Expert
    Studio Omega
    Bydgoszcz
    Poland
    ------------------------------



  • 4.  RE: G7 with Light Fast Inks

    Posted 10 days ago
    Hi Wojciech,

    My 300% CMY is a*-4​ b* -4, but that is probably because we backed off the Y,M density slightly to help with trapping, I think changing the ink order would help for sure, but we would need to get different tact ink. Even with that change I don't think we will match Gracol, after doing a G7 calibration through Curve 4 my CMYKRGB are passing, my Delta L passes, my Delta CH is awful.

    ------------------------------
    Greg Sterwald G7 Professional
    Prepress Manager
    Crossmark Graphics Inc.
    New Berlin WI
    (262) 821-1343
    ------------------------------



  • 5.  RE: G7 with Light Fast Inks

    Posted 10 days ago
    300% CMY isn't bad - so you should be able to calibrate Gray Balance.
    Earlier you mentioned that the problem is above 50%.
    Curve4 Calibrate has a Gray Balance tab in the Create Curves options.
    Make sure you have set the Gray correction featheter-off parameter to a smaller range, eg Start 90%-95%, Stop 100% - this will make the curve corrected more strongly in this area.
    Also make sure you have Gray Balance selected near the Export button.

    Another important thing is also when printing to get a register - maybe additional register marks to match around P2P and Gray Balance patches.

    Make sure the Run-to-Run deltas are really low as you make subsequent curve adjustments. ( Analyze > Ink & Substrate > Run-to-Run ).

    ------------------------------
    Wojciech Bialkowski G7 Expert
    Studio Omega
    Bydgoszcz
    Poland
    ------------------------------