Delta E on mag/yellow combination is high

[jbarrie]

I am profiling some paper for an Epson 9880 using the GMG color management system and I’m having trouble getting satisfactory results. With both papers (EFI Validation and Epson SemiMatte) the average delta E reading is pretty good, both coming is around .5. The problem is the magenta/yellow combinations seem to linger on the high side ( 3.7 to 4.6 delta E readings).
I never had this problem with the older 9800 plotter using 6 color inks; it seems the moment my company got the new 9880 using the vivid colors, the reds would not come down properly. Has anybody ran into this problem or am I missing a step with the profiling process that would cause this to happen. Thanks in advance.

 

[TerryWyse]

Are you talking about the delta e during a re-calibration not falling in line or the delta e of a profile? The peak delta e values in an MX4 profile could be on the high side only because the target Lab values could be out-of-gamut for your printer/paper/ink combination. Having said that, using a data set (target values) from something like GRACoL Coated1, you shouldn't see max delta e values much over about 3 (I routinely achieve <2 dE peaks on good media using GRACoL as a target).

If you're talking max dE values during a re-calibration, it could be any number of things:
* A less than ideal "starter" calibration MX3. Creating a custom starter MX3 is a bit involved but if you do it carefully, you can achieve stellar results. If you've used a "generic" MX3 starter kit however, you could run into problems like you describe. I'm assuming you're using a starter MX3 that's specific to your media/ink/printer/output settings combination.

* You may need to create a new "linear" gamut file. 9 times out of 10, if a printer all of a sudden won't calibrate to within tolerance anymore, you should make sure the printheads are clear and possibly create a new linear or "full" gamut file and tag that to your current calibration MX3 file. The first time you calibrate with the new linear gamut file, you should set your delta e tolerance to *zero* and go through as many iterations as necessary to bring the dE tolerance down as low as it will go. After you've done that, reset your dE tolerances back to production values. Also, I would suggest using a testchart for the gamut file that uses upwards of 2,000 patches (I use over 6,000 patches). The critical thing is having a couple of extra "fulcrum" points in the 85-100% range which is where you'll generally run into some inking variations.

My guess is that you've got some slight over-inking in yellow+magenta overprints that are causing this variation in max dE values. A new "starter" MX3 is about the only way to correct this.

Contact me off-list if you'd like some more detail

Regards,
Terry

 

[caveman]

.... if a printer all of a sudden won't calibrate to within tolerance anymore.....

Hello Terry,

could you give some reasons why this may occur? What about adjusting the paper feed? Could this "correct" this behaviour (the "won't calibrate within tolerance" behaviour I mean)?

thank you in advance

caveman

 

[jbarrie]

Terry, Yes the problem is a new MX4 file and not just a re-calibration. I noticed that in my injet mode when creating the MX4 was set to 90% max key and 0% for the start key (manual suggests 95% max and 5% start) do you think this could contribute the the high magenta/yellow combinations? With regards to the starter kit, I used the "Starterkit_Epsonx880_8c_V1" version I downloaded from GMG. Is this the correct one?

Thanks,
Jeff