Digital Printing and ISO12647/2846

[jlind]

I'm interested in how well the various digital color printing CMYK primaries stack up to ISO12647 and ISO2846. Seems like our Indigo operator struggles a little more matching reds from Hostman Steinberg sheetfed primaries. Is he alone with this issue? He gets reasonably close. I've noticed that in the case of an Indigo, when you print out a color look up table on coated and uncoated paper, they are identical in hue, meaning that the colorants sit on top of the sheet no matter what the paper surface. The offset inks have less holdout for sure. It might just be surface issues. Can anyone comment on how close they are in CIELAB to ISO2846? Did they do this in any recent benchmarking study, like IPA?

John Lind
Cranberry Township, PA
724-776-4718

 

[StrikTenn913]

Hi Jilind,

Check out 2009 Digital Print Forum Overview | IPA

IPA recently did the above study. Some of the measurements are based off of ISO 12647.

 

[meddington]

Note that the IPA study compares a devices ability to match the Gracol and SWOP characterization data sets and reports average and 95th percentile delta E76 values. If your looking specifically for primaries toward 12647-2, those aren't included individually in the study. Nice thing is the physical print samples from each device are included, so you could measure them.

FYI, our Indigo 5000 can hit the ISO12647-2 primaries very well when color-managing the device. Without color managment, the cyan and magenta fall slightly outside of spec.

Without Color Management (pure primaries)
C: L*: 55.43, a*: -32.55, b*: -52.47 dE76: 5.1
M: L*: 50.33, a*: 76.48, b*: 2.75 dE76: 6.68
Y: L*: 89.72, a*: -5.58, b*: 91.69 dE76: 1.60

WITH Color Management
C: L*: 54.4, a*: -37.6, b*: -50.4 dE76: 0.93
M: L*: 47.7, a*: 73, b*: -3.2 dE76: 1.06
Y: L*: 89.1, a*: -4.6, b*: 93.0 dE76: 0.41

I don't have a practical way to measure the inks toward ISO2846, and the inks themselves don't seem to make any claims here...no documentation as such.

And yes, ink hold out on Uncoated is much better than offset. All "uncoated" stock we've run has actually been coated (saphire if that's what they're still using) for Indigo use.

 

[jlind]

Well, what did it say? You certainly don't expect me to BUY it do you? That's for vendors to buy and give to sales prospects. How about an executive summary? From the outline, it doesn't appear that they addressed the issue, except maybe on the GRACoL category. To really address the ISO2846, they would have to feed some UGRA APCO II/II paper into the Indigo and make a few measurements. Anyone done this?

John Lind
Cranberry Township, PA
724-776-4718

 

[meddington]

Well, what did it say? You certainly don't expect me to BUY it do you? That's for vendors to buy and give to sales prospects. How about an executive summary?

What, for free? The Indigo 7000 was used in the 2009 Digital Print Forum, and scored well for average and 95th percentile using the ISO 12647-7 tolerances. The 2008 Forum had an Indigo 5000 model participating (ours actually) and they actually measured primaries toward ISO12647-2, which is missing from the 2009 version. Our Indigo was within tolerance of ISO12647-2 with the exception of magenta, which measured over 8 delta E 76 with their spectro. These primaries were not color managed mind you. In fact, all magenta primaries were similar between the digital print devices.

 

[rich apollo]

Would 2846 be applicable to digital? I kind of assumed that it wouldn't.

 

[Mike Strickler]

Digital Printing and ISO12647/2846

Since the comment was specifically about reds, part of the problem may be that Indigo 2-color overprints (R, G, B) vary a bit from litho as there is no wet trapping effect to speak of. There is nothing to prevent you from making a device link to convert your files to an Indigo profile. If you want to match regular offset closely you need color management.

 

[jlind]

Thanks for the good information. I'm surprised someone hasn't done an ISO2846 on an Indigo. This machine is a 3050, so, no color management at the RIP. Amazing that it is as close as it is. Yes, Device Link Profiles would make it closer, but it is so close most of the time it may not be worth the effort.

Thanks again
John Lind
Cranberry Township, PA
724-776-4718

 

[rich apollo]

You can set up an Acrobat Preflight droplet to perform the necessary color transform upstream from the RIP. Would also be a way to handle spot colors, RGB images, etc.