My question is how far out can your gray balance be at standard densities and the software still be able to create individual cmy curves that will result in gray balance?
Reason I’m asking is we find gray balance on press with linear plates at 148-135-100 cmy, and used one curve. Now we seem to be having trap issues with the CM and would like to bring the cyan density down but when we print the grayfinder target at standard density 145-145-100 cmy it is way too red overall to find a gray patch on it that’s useable to plot individual curves manually. Can anyone tell me if there is a way to do this manually in this case or if the software will take care of this for me?
I need to be able to do it manually so press can go back to standard densities and maybe get rid of CM trapping problem, or be able to justify the cost of the curve software to do this for me if no way to do it manually?
If the process is stable, IDLCurve shouldn’t have a problem getting you good compensation curve for gray balance. But a few things to consider…“standard densities” are not a measurement of color. How are your primary solid ink Lab values conforming to standard Lab values? Knowing where this lies, and how close the secondary overprints are to published value will give you insight into how far you can move primary ink density toward optimum Lab values for both primary and secondary. Once your targets are established, you can then establish compensation curves for gray balance (as well as derive target density values for production), but again, the stability of the device is thedeterminingfactor for success, rather than a densitometric value. Averaging is recommended.
I have to agree with Mike’s response in regards to Lab vs. density. That being said, your ”standard densities” are more in line with where I have hit the Gracol /ISO solids, and I can see why you would be having trap problems at the other densities.
I assume you are printing the P2P25 target if you are attempting Gracol calibration. Rows 6-12 are the various gray balance combinations that Curve uses to do its calculations. The steps are in 5% increments, but you can interpolate, or at least make an educated guess using those patches as a guide.
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Bret Hesler
Earth•Thebault, Inc.
Parsippany, New Jersey
Yes, our process is stable and we have been running this way for over a year now. When we did our G7 test run we did find gray balance on press at 148-135-100 cmy so we used one curve for all 3 and it has worked well, only lately we’ve begun having cm trap issues and can’t seem to get that resolved.
Everyone seems to agree that putting down the heavy cyan and then lighter magenta is probably what is causing this, so we’re thinking of getting the curve software to be able to run “standard” density and have it calculate the gray balance, which I assume would be with individual cmy curves. And yes, our solids were within the Lab tolerances at those densities, in fact with an ink we recently started running were better than ever, a little over a deltaE of less than 3 for almost all 7 primaries.
We just have such a red cast at “standard” densities and dot gains, I was wondering if the software would be able to account for something that far out?
Thanks for the earlier responses. When preparing for a new calibration run the press crew found 2 units were overpacked on the plates, looked like they were packed for .008" plates and we’ve always used .012", they use a perma pak and its been on the press since install in 2000. They also found one unit where the blanket didn’t have enough packing and was even with bearer instead of .002" over? We have had problem with printing to heavy magenta always, I’m interested to see if fixing these problems will affect that in any way.
