Where can you purchase printed Gracol targets?

[JoshB]

My Google-fu seems to be weak today; I can't for the life of me find anyone selling hard copies of the ideaAlliance G7 forms. Anyone have a link?

[chevalier]

Why exactly would you want to buy one?

[JoshB]

Well, I do understand that it's meant to be a tool to help you reach a valid G7 state rather than a check sheet or spectro-photometer calibration tool.

The thing is I'm trying to work with several different printers. In the mix are several different digital color presses, a DI, several different 4-color offset presses, different papers, etc... All the things that G7 is supposed to help you deal with. Everybody claims that they are calibrated, that they are doing it right, but not a single process matches any other, and none of them match my soft proof.

So, while there's obviously a lot of work to do there, it sure seems like it would be helpful to start from "Here's what it ought to look like".

[gordo]

Well, I do understand that it's meant to be a tool to help you reach a valid G7 state rather than a check sheet or spectro-photometer calibration tool.

The thing is I'm trying to work with several different printers. In the mix are several different digital color presses, a DI, several different 4-color offset presses, different papers, etc... All the things that G7 is supposed to help you deal with. Everybody claims that they are calibrated, that they are doing it right, but not a single process matches any other, and none of them match my soft proof.

So, while there's obviously a lot of work to do there, it sure seems like it would be helpful to start from "Here's what it ought to look like".

G7 is a method to grey balance output devices - that does not mean that the colors will match across devices. Calibration simply means that a device is brought to a known state - it does not tell you what the color looks (or measures) like.

Idealliance used to sell certified GRACoL 7 press sheets so that printers would have an example of what a press sheet that conforms to ISO 12647-2 looks like. But AFAIK they no longer provide such a reference.

Methinks you need to find out what the different printers you work with are calibrated to. What they likely should be targeting is what's called ISO 12647-2 or GRACoL 7 (which is based on ISO 12647-2 specifications). Then you can use a spectrophotometer to confirm conformance. You also need to confirm that your proofer conforms to ISO 12647-2.

You are diving into deep waters.

best, gordo

[JoshB]

Thanks, Gordo. I definitely know just enough to get myself into trouble. What's frustrating is that so many printers don't even seem to know that. I know two large offset printers that didn't even linearize their presses, I'm not sure anyone even understood the concept that you'd have a press profile or reference conditions. They've just got a pressman yanking ink levels back and forth on a per job basis until it "looks right". I really don't understand this industry sometimes.

I'm a software guy writing web-to-print tools. "Upload your file and we'll just take care of it" kind of stuff. I know barely enough about color that when I'm at a production facility, if I'm lucky and have the manuals and instructions right in front of me, I can get things calibrated and get pretty good matches across locations. As soon as I leave we start getting customer complaints and I find that we're weeks out of calibration, or somebody in pre-press changed the automated workflow, or who knows what crap... it amazes me.


Phew. OK. Let me get off my soap box before I trip and fall on my head.

Basically from what I think I understand about the G7 process. The goal is to develop a standard set of reference conditions for a press, paper and screening so that when you run to a set of standard densities you can know that several defined CMYK values will produce a neutral gray. If this is true, then you can reliably expect the overall hue and value of the image ripped through that same process to be very consistent, even on different presses. An individual spot color may not match perfectly, but overall image "A" should look very similar to image "B"; the color balance should be the same, and contrast should end up the same.

For digital presses there doesn't seem to be an effective way to apply the curve-adjustment algorithms (please correct me if I'm wrong). But I'm not sure it matters anyway, because you should be able to use the Gracol Coated profile and the color management of the digital press should do a pretty effective job, producing --again-- not necessarily an exact match but a result that should generally satisfy most customers.

So, I'm looking at trying to develop quality control tools. I already know I'm going to get he-said/she-said push back if I try to compare one printer's output to another. It seems to me like the only way I'm ever going to get a good start is to be able to come in and say "Look. here's an example of a working implementation. This is the standard. Now we're going to iterate through this process until we can achieve something like this, and you're going to make sure that you can keep producing this going forwards."

[gordo]

What's frustrating is that so many printers don't even seem to know that. I know two large offset printers that didn't even linearize their presses, I'm not sure anyone even understood the concept that you'd have a press profile or reference conditions. They've just got a pressman yanking ink levels back and forth on a per job basis until it "looks right". I really don't understand this industry sometimes.

Yes, that's often the case. BTW you don't linearize a press (unless you're using the term to mean something different).

Basically from what I think I understand about the G7 process. The goal is to develop a standard set of reference conditions for a press, paper and screening so that when you run to a set of standard densities you can know that several defined CMYK values will produce a neutral gray.

The standard reference condition is ISO 12647-2. If the printer is set up to hit ISO 12647-2 then the G7 method can be used to calibrate the printing process so that it is in grey balance. But if the various printers are not set up to hit a common standard but use G7 to grey balance then you'll have presswork from different printers that are in grey balance but the colors will be different.

If this is true, then you can reliably expect the overall hue and value of the image ripped through that same process to be very consistent, even on different presses. An individual spot color may not match perfectly, but overall image "A" should look very similar to image "B"; the color balance should be the same, and contrast should end up the same.

The key is that the proofs supplied by the different printers should closely match if they are targeting the the same print standard. One then assumes, hopes, and/or prays that the printer can match their own proof. And if your proof is set to the same standard then your proof should be a close match to theirs.

For digital presses there doesn't seem to be an effective way to apply the curve-adjustment algorithms (please correct me if I'm wrong). But I'm not sure it matters anyway, because you should be able to use the Gracol Coated profile and the color management of the digital press should do a pretty effective job, producing --again-- not necessarily an exact match but a result that should generally satisfy most customers.

The ability to do curve adjustments would depend on the workflow and type of digital press. But you're pretty much correct.

So, I'm looking at trying to develop quality control tools. I already know I'm going to get he-said/she-said push back if I try to compare one printer's output to another. It seems to me like the only way I'm ever going to get a good start is to be able to come in and say "Look. here's an example of a working implementation. This is the standard. Now we're going to iterate through this process until we can achieve something like this, and you're going to make sure that you can keep producing this going forwards."

These are the deep waters. For QC purposes you can insist that a color/print control media wedge be included with every proof. That way you can check that proofs from the same printer are consistent and you can compare the proofs of one printer against another to see if they are both targeting the same standard. However, if the printer(s) is not committed to printing to a standard (embodied in their proof) then it is doubtful that they will change to accommodate you unless you are a major customer since their cost to make the change would be significant.

best, gordo

[chevalier]

I have a halftone proofer (Fuji/Luxel FinalProof), an inkjet proofer (Epson 9900 with Integrated spectrophotometer) and two printing presses (I'm working on getting Heidelberg's ImageControl certifying/tracking conformance of each press sheet pull) all calibrated to near-GRACoL7 standards (my paperwhite tolerance is <3.5dE rather than <3) and gray balanced via the G7 process. Each device was independently calibrated without reference to the others. Then the two proofs and a press sheet were laid next to each other. The match isn't absolutely perfect but is by far the most accurate and most consistent I've seen achieved. I was very doubtful about this process until I saw it happen and the results it achieved before my own eyes. The trick to maintaining this is certification of conformity - we run a color/print control media wedge on every proof. With digital presses I've heard of running a wedge before and after the job as a means to certify as generally digital work does not accommodate enough excess paper space for a control wedge. On offset printing presses a lack of sheet space problem also occurs but the color bars on the press sheet can be read in via some color control consoles. Logging all of this data in a central database that is easy to access and user friendly is a big obstacle. Fujifilm has made huge inroads into this problem with the Colorpath/Taskero Universe product.

Some informative/useful links:
G7 vs. GRACoL explaination:
Do you know the Difference between GRACoL, GRACoL 7 and G7? | IDEAlliance

Listing of G7 printers and experts:
Master Printer Database - Welcome

Fujifilm's Colorpath/Taskero Universe System:
ColorPath (Taskero Universe) | Consultative Services | Graphic Arts & Printing | Fujifilm USA

[JoshB]

OK, now you've got me worried that I've got some really basic misconceptions, Gordo.

Isn't press linearization pretty much step one for any standards process? I want to be able to say 30% and get 30%, right? That seems to be fundamental.

[Correct Color]

For digital presses there doesn't seem to be an effective way to apply the curve-adjustment algorithms (please correct me if I'm wrong). But I'm not sure it matters anyway, because you should be able to use the Gracol Coated profile and the color management of the digital press should do a pretty effective job, producing --again-- not necessarily an exact match but a result that should generally satisfy most customers.

Actually, this is pretty far off the mark.

Fact is that what the entire G7 process began as an attempt to duplicate in offset lithography the linearization process that's already included somewhere in the routine of every RIP-driven digital printing device.

Once you're creating dots digitally it's to all that difficult of a process to establish a routine to do some sort of calibration/linearization (the terms loosely used somewhat overlap.)

Of course it's much harder to do on a litho press because of all the variably factors involved, and up until digital plate making, it was pretty much impossible.

But of course now it is possible, but to say it's more difficult to achieve a linear state in a digital device than a litho press has it exactly backwards.

However, the Gracol profile does nothing to achieve linearity or grey balance--it assumes they're already achieved. And understand that color management on a digital device is something that has to be done. It doesn't come in the box from the factory. If you want to attempt to hit a Gracol proofing standard with a digital device, first you have to calibrate and characterize the device, and then you have to send that device images in the Gracol colorspace. How well you do the calibration and characterization will determine how pleased you'll be with the result you get.


Mike Adams
Correct Color

[rich apollo]

OK, now you've got me worried that I've got some really basic misconceptions, Gordo.

Isn't press linearization pretty much step one for any standards process? I want to be able to say 30% and get 30%, right? That seems to be fundamental.

Not exactly. One might linearize the platesetter to ensure correct exposure, et cetera. I actually quit linearizing platesetters long ago. I get better results with the natural response of the plates. You must linearize an inkjet proofer before profiling. But, you don't 'linearize' a press.

It sounds like you're operating from the position that dot gain is a bad thing. It's neither good, nor bad, it just is. You can set up your platesetter so that a 30% in the file will yield 30% on press. I've done it, and it looks like crap. Trust me, we like dot gain. Printing without dot gain looks hollow and sharp. I've never ended up using linear plates. Some level of adjustment has always been applied to pull the plate out of linearity.

If you look at the ISO 12647-2 TVI curves and/or the G7/GRACoL NPDC, none of them are 'linear'. They all exhibit non-linear responses. What you're attempting to do is get your presses' dot gain responses to align with the dot gain of the standard you want to match.