Epson 7900 Inline Spectro

[jmp_pai_2]

Oris Certified Web report from your TXT file "G7 Sync Digital Page 11x7_FOLD1_FRONT_3.txt" is attached.

Got it, Thanks for all your input. We have our work cut out for us, always trying to learn and improve.

 

[jmp_pai_2]

You need to use the dE formula required by the specification being proofed. For example, with Fogra39 / ISO Coated v2 – one has to use dE 76 / dE ab. This should not be an arbitrary choice or based on whether a machine is inkjet or toner based. Calibration is different, however we are not discussing calibration here but certification to a specification.


Stephen Marsh

I am not sure I understand, could you please explain. Thanks.

 

[chevalier]

I am not sure I understand, could you please explain. Thanks.

There's basically an ISO standard that dictates what dE formulas IDEAlliance is using to qualify you as GRACoL, SWOP, G7, etc. If I am up to date they are still using dE76 as commonly known as generic "dE". There is significant argument as to whether dE76 should remain in use.

A 2009 printplanet thread about GRACoL + G7 proofing:
http://printplanet.com/forums/color-management/19385-delta-e-equation-gracol-g7-proofing

More info about Delta E formulas
ColorWiki - Delta E: The Color Difference

From the ColorWiki (owned by chromix [basically Don Hutcheson's word of gospel])

Finally, which equation should be chosen and how should it be used?

for basic / fast calculations, you can use dE76 but beware of its problems
for graphics arts use we recommend dE94 and perhaps dE-CMC 2:1
for textiles use dE-CMC
Editor's note:
Since this article was written, dE2000 has become the industry standard formula to use. dE2000 is recommended for all calculations except textiles which still use dE-CMC.

 

[Stephen Marsh]

chevalier did a good job of explaining. When you calibrate a device, I would avoid using dE76/ab due to it’s known limitations. I would use dE94 or a later formula if offered by the calibration software. Once the machine is calibrated, you run your print/proof. Next comes verification to a specification. The specification may call for proofing validation to be calculated using dE76/dEab formula. One should not use a different formula than the specification requires, otherwise the validation is void/useless in that context. Outside of industry specifications, one can of course use whatever formula they like for “in house” specifications.


Stephen Marsh

 

[jmp_pai_2]

chevalier did a good job of explaining. When you calibrate a device, I would avoid using dE76/ab due to it’s known limitations. I would use dE94 or a later formula if offered by the calibration software. Once the machine is calibrated, you run your print/proof. Next comes verification to a specification. The specification may call for proofing validation to be calculated using dE76/dEab formula. One should not use a different formula than the specification requires, otherwise the validation is void/useless in that context. Outside of industry specifications, one can of course use whatever formula they like for “in house” specifications.


Stephen Marsh

Thanks Chevalier and Stephen, your insight is helpful. The more I learn, the more I realize don't know.

 

[Johu]

Also as you mentioned earlier you only have the black backing on the printer. Depending on your paper (mostly opacity) the different measuring backgrounds can cause a problem. But it does not explain why it worked for some time before it started to fail.
What I would like to see is the measurement file from the i1, just to compare it with the ILS measurement.
BTW. the 2.0.5 on the CGS website is different build than the one on the CTW 3 installation file, even if they both are 2.0.5.