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  • 1.  Alternative Approach to Passing G7 without using Normalize High Density in Curve4

    Posted 02-15-2022 11:41 AM

    Hi there everyone! Last time I was here I was questioning why I wasn't passing grayscale on the TC1617. The reasoning behind that had to do with my (older) spectro device was not picking up the grayscale boxes correctly. We don't have an i1iO so I had to rotate the chart, add lines between low percentage grayscale boxes and everything worked out fine. We were having problems still, with passing Colorspace in CRPC6 so that leads me to this question.

    After research, I've found out that the reason we are not passing targeted is because of high densities in the latter percentages. Specifically 75-100. To combat that, the solution was to "Normalize high densities" in Curve4 and finish the calibration out in Gracol2006. For some reason, this bugs me. I want to be able to hit CRPC6 without finding a work around. I know the HP Scitex 15500 has a bit of a green problem in yellow ink, but until I try everything, I don't believe we can't do it. Now my real question.

    Am I being naive by thinking I can manually move my curves to compensate for the high densities? I've achieved passing grayscale, and a close call on targeted. I am on my third P2P51x chart currently. For all intents and purposes, I feel as though it's not that far fetched to make some pretty common sense moves when manually moving lines. The charts prior to me moving them had a sharp spike at the end of the chart so I looked into the output values in 5% increments and continued the pattern instead of having them jump up 20%.  Then I printed a new chart, analyzed it, made some adjustments to the black and magenta lines, analyzed it and scanned it in and now I'm here, with a seemingly very normal TVI and npdc, thinking that maybe I could pull it off this way? 


    It's definitely not "the norm" and I'm not trying to cheat the process, but I don't like going down without a fight haha. Any insight, information or forseeable roadblocks are absolutely welcome and encouraged. Thank you!! 

    (adding my charts for reference)



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    Alexis Brennan G7 Expert
    Sutherland Packaging
    Andover NJ
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  • 2.  RE: Alternative Approach to Passing G7 without using Normalize High Density in Curve4

    Posted 02-16-2022 12:16 PM
      |   view attached
    One thing I've done in similar situations is to limit the 100% of each color so they are closer to the the target L* value. I'm not sure what rip you're using, but I know you can do it in Caldera when you're at the linearization stage. I don't do this all the time, but it's helped on some troublesome substrates.(see my  attched screeenshot)

    In Caldera. you'd adjust the Pmax value until the measured L* value was closer to the color's target L* value, which in your case would be about 87. I don't know if this would work on CMYK+ printers though and if your base ink is just too greenish, you may never get there.
    Note: you'd have to do this for all 4 colors, run your ink limit chart, then come back and do the g7 lin and then profile from there. It's not a great system but it can help with getting a smoother NPDC curve in some situations. 


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    Brian Tickenoff
    PrePress Manager
    Coyle Reproductions Inc.
    Brea CA
    (866) 269-5373
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  • 3.  RE: Alternative Approach to Passing G7 without using Normalize High Density in Curve4

    Posted 02-16-2022 12:58 PM

    Isn't that done every single time I relinearize with a cgats correction curve? I think we are explaining the same process, just differently. When I say I'm changing the linearization curves by hand, I mean I'm resetting those end values and smoothing out irregularities of the final curves after inserting a correction. My last P2P51x had cyan stop at 53.8, yellow at 63.3, yellow at 73.9, and black at 96.5, so I think we are on the same page? Or I am entirely misunderstanding you and in that case, please explain further. 

    To answer your question we are using Caldera as well. I'm going to attach the curves I am working on first and then the curves that normally happen when we use Curve4 for G7 calibration without normalizing high densities.

    I will say - if we click the "normalize high densities" button in Curve4 - we definitely do get better results, pass grayscale and sometimes even targeted within one correction - but - I'm trying to figure out how to pass Colorspace in CRPC6, so in that sense - we are still struggling.

    I apologize for the confusion. My wording is sometimes more complicated than it needs to be.



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    Alexis Brennan G7 Expert
    Sutherland Packaging
    Andover NJ
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  • 4.  RE: Alternative Approach to Passing G7 without using Normalize High Density in Curve4

    Posted 02-16-2022 01:09 PM
    With that explanation, I think we are talking about the same thing. 
    That lin curve looks really odd. I'm not too familiar with your press but I'd suggest calling one of their application specialist if you haven't already. I deal with them for our Latex presses and I'm usually able to get some good tips from them.

    Have you tried to create a G7 lin after you do your base lin and total ink limit? I'll do that and use the g7 verification tool in caldera to make sure my greyscale (and hopefully my CMYK solids) are within spec BEFORE I create my profile.

    ------------------------------
    Brian Tickenoff
    PrePress Manager
    Coyle Reproductions Inc.
    Brea CA
    (866) 269-5373
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  • 5.  RE: Alternative Approach to Passing G7 without using Normalize High Density in Curve4

    Posted 02-16-2022 01:21 PM
    That's our normal process, yes. We print and scan our light magenta and light cyan transitions and then we print and scan our standard CMYK linearization and we get a very traditional, normal looking curve result. The ink limit is set, normally to 180 in satin appearances, and then we print our first P2P51x from Caldera. I scan that P2P51x into Curve4 to get my first correction curve and it looks - crazy because of a dramatic spike in the high densities. The values up until 75% are all very normal in terms of traditional curves, but the high densities are not.

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    Alexis Brennan G7 Expert
    Sutherland Packaging
    Andover NJ
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  • 6.  RE: Alternative Approach to Passing G7 without using Normalize High Density in Curve4

    Posted 02-16-2022 01:31 PM
    GoOtchya. I think the one step that I do differently is that after I set my ink limit, I immediately go BACK to the lin page in Caldera and do a G7 curve there then profile from there. After that, I'll print my TC1617 and verify it in Curve4 and hope it passes. If it doesn't due to solid ink patch failure, then I don't believe any amount of curving will help unfortunately.

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    Brian Tickenoff
    PrePress Manager
    Coyle Reproductions Inc.
    Brea CA
    (866) 269-5373
    ------------------------------