Which Delta E equation for Gracol G7 proofing

[Colorblind]

Hi everyone, I'm trying to fine tune my proofing system to Gracol G7. So far I'm pretty close to the target values if I'm using CIE 1994 Delta E equation. Is that the proper equation I should be using or another one such as CIE 2000?

 

[TerryWyse]

At this point, I don't believe there's any agreement on which of the "alternate" delta e formulas to use. Tolerances are assumed to be "straight" dE (dE76). Off the top of my head, I believe the tolerance MUST be below 5 dE76 for solids and SHOULD be below 3 dE. Grays I believe should be < 1.5 dE.

Assuming these are the correct dE tolerance values, they only work for dE76...you must lower the tolerance for either dE94 or dE2000. There's no hard and fast rule for this due to the complexity of the dE2000 formula but I would expect dE2000 tolerances to be roughly 2/3 to 1/2 of the dE76 values....as a guess. dE2000 is generally more sensitive to delta L* and delta hue than it is delta chroma.

Regards,
Terry

 

[Colorblind]

That makes a perfect answer. Thank you.

 

[sussobe]

That makes a perfect answer. Thank you.

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[Werby]

"Official"

"Official"

For the record, the ISO 12547-7 tolerances for "certified" proofs is:

dE76 paper < 3
de76 avg < 3
de76 max < 6
de76 primaries < 5
dH primaries < 2.5
dH avg cmy gray < 1.5

There are no official tolerances published by GRACoL themselves, and the ISO hasn't incorporated dE2000 as an official metric quite yet, so technically you have to stick with "vanilla" delta-E.

 

[lucascalvo]

The last thing I know you must make a it-8 of the printing and measure the proof in Profile maker and the averange of the 95% of all the colors must be > 1.5 Delta E. and the max must be >6. I hope this help.

 

[Eric van der Kop]

Standard for Digital Printing for Fogra Certified printing

Standard for Digital Printing for Fogra Certified printing

Iso is working on a new standard for Digital print presses. ISO-12647-8 Validation Print.
This is going to take some time.

For Digital "'Proofing"' the standard is more secure then for the Fogra Certified for digital printers. Gracol standards and Fogra are in fact not realy different. But that is an other discussion.

The standards use for Fogra Certified printing are:
3.0 Max. average all patches.
8.0 Max. peak all patches.
8.0 Max. average outer gamut patches
8.0 Max. peak for 95% of patches
5.0 Max. average CMYK patches
5.0 Max. peak Cyan
5.0 Max. peak Magenta
5.0 Max. peak Yellow
5.0 Max. peak Black
2.5 Max. peak CMYK patches
1.5 Max average Gray patches
5.0 Max. peak CMYK patches
Delta E format CIE L*a*b* references D-50 Gamma 1

 

[meddington]

The last thing I know you must make a it-8 of the printing and measure the proof in Profile maker and the averange of the 95% of all the colors must be > 1.5 Delta E. and the max must be >6. I hope this help.

I believe what you're describing (aver dE76 under 1.5, 95th percentile under 6) is actually the tolerance for Proofing System Certification, which is not currently applicable to daily production proof verification. There are a few problems with mandating these tolerances for production proofing, notably that inter-instrument agreement is such as too make them too tight for practical use.