Interesting. So how do results look before the iteration in GMG? Is it already looking problematic, with higher-than-expected dEs for that stage? Is so, something else is going on in your print process that is making it hard to make a good output profile, and this will limit the improvement possible with further profile tuning. Can you share the results from a fresh, non-iterated profile?
Original Message:
Sent: 01-24-2025 02:12 PM
From: Randy McDonnell
Subject: w∆Ch fail with Curve4
Thanks to all for your comments and suggestions.
Native CMYK on/off didn't change anything.
The substrate is white BOPP.
Both P2P51 and TC1617 show similar results (fail).
Not seeing ink trapping or skipping issues.
This is Mark Andy HD digital press that is being color managed via GMG ColorServer Smart Profiler. Creating a new profile from scratch does not change the result. GMG also has a recalibrate function that 'fixes' existing profiles back to their original - which helps when initially passing G7 and now the profile has drifted. This recalibrate did not change anything.
We run this TC1617 chart every 4-6 months to confirm our profiles are still within g7 specification. Run it for all the various substrates and profiles we have. If is fails, we first try to fix with a recalibrate and if this doesn't solve the issue (as is the case here) we build a new profile from scratch.
This is the first time ever over a few years now that a failed G7 reading was not fixable by rebuilding a new profile from scratch or a recalibrate. Other profiles are passing G7 currently. We follow a strict procedure so that any new profiles have the exact same settings each time around - nothing has changed in our color management.
This particular iteration is V8 meaning the 8th new version of the same profile for this substrate over time. 7 previous times, no issues, hit G7 right away. This 8th time, no such luck.
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Randy McDonnell - G7 Expert
Prepress
Kwality Labels Inc
Richmond Hill ON
(905) 780-9496
Original Message:
Sent: 01-24-2025 01:22 PM
From: Mike Strickler
Subject: w∆Ch fail with Curve4
IIRC, the digital press colorspace qualification is the same as for a conventional press, which does also require a grayscale pass. I have sometimes seen this issue when working with inkjet proofers, in which the normal profiling and iterative optimizing fail to dial in the gray balance as much as expected. Usually there was an issue outside color management that was at fault, e.g., with the driver. I like Tim's suggestion to disable color management, and in this condition I would apply the curves suggested by Curve and check the result. Then I would profile on top of this. This is the recognized best practice for conventional presses and may help in this case. Then of course you can iterate as before if this further improves the result. I should add that you shouldn't reverse this order and apply G7 curves on color-managed output. It doesn't work!
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Mike Strickler
MSP Graphic Services
Original Message:
Sent: 01-24-2025 08:49 AM
From: Timothy Quinn
Subject: w∆Ch fail with Curve4
Native wouldn't help because his 100x3 ink is nearly 0,0.
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Timothy Quinn
Consultant
Nazdar Consulting Services
Shawnee KS
816-582-6748
Original Message:
Sent: 01-24-2025 08:40 AM
From: Donald Barr
Subject: w∆Ch fail with Curve4
Try turning on Native CMYK. Sometimes the 3 color gray don't blend well. See if that works.
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Donald Barr G7 Expert
Color Management Consultant
SK Digital Services LLC
Lusby MD
(443) 624-4578
Original Message:
Sent: 01-23-2025 03:11 PM
From: Randy McDonnell
Subject: w∆Ch fail with Curve4
Reading a TC1617 chart on a Mark Andy HD digital press for G7
Within Curve4 everything else (Targeted and Colorspace) is passing - just a w∆Ch fail.
Tried re-profiling from scratch (GMG), tried re-calibrating profile, various substrates - and pretty much a consistent w∆Ch fail each time.
What do I need to think about adjusting or changing to get a pass?
Thanks,
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Randy McDonnell - G7 Expert
Prepress
Kwality Labels Inc
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