G7 certification and Heidelberg Color Training

[prepressguru]

We aiming to get our G7 certificate. Currently we have invested in Heidelberg Image control and Color Tools. Which I find to be a great set of hardware and software. Been through the training and matched our proof to press, and calibrated to near neutral. Recently had a visit by a service group which helps with G7 certification. To me it looks like the steps I have learned from Heidelberg are very much the same. I suggested we run the G7 form without their help then submit it.

Does it seem like I am on the correct track?

 

[meddington]

We aiming to get our G7 certificate.... I suggested we run the G7 form without their help then submit it.

You're referring to G7 Master Printer Qualification (not certification) status, correct? Per Idealliance, Master Printer Qualification must be performed by a certified G7 Expert.

 

[uscollins]

G7 Master Qualification

G7 Master Qualification

IDEAlliance

This link should answer most of your questions for G7 Master. You can contact Idealliance, for further details. [email protected].

A qualified G7 Expert must be present for G7 Master qualifications.

 

[Chuck Koehler]

To all concerned,

Heidleberg can offer any Heidelberg customers SPECIFIC training and IMPLEMENTATION in G7 using Heidelberg Equipment and processes, at the end of which they can recieve Master Printer Qualification directly from Heidelberg Certified G7 Experts.

Heidelberg has specific tools available that can acheive the G7 Objectives with very little effort - especially if you already own Image Control and Color Toolbox. Heidelberg Representatives are the most qualified and best suited to help a Heidelberg Printer become Master Printer Qualified. Using other third party independant G7 Experts and procedures will very likely end up in less accurate results and ineffective employment of Heidelberg Technology.

Most - if not all - other G7 Experts have very little idea on the proper use of Heidelberg Equipment and very often give false or misleading statements on what is or isn't possible with Heidelberg Technology. Many many times we have heard stories from our customers who tell us that an independant G7 Expert has told them they could'nt obtain G7 Master Printer Status using one piece of Heidelberg Equipment or another. This is patently false, misleading, and causes Heidelberg customers to LOSE MONEY investing in inferior solutions while at the same time not utilizing the sophisticated technology that they have ALREADY INVESTED in.

Color Bars are a prime example of this. There are NO REQUIREMENTS for using any particular Color Bar for G7. There is NO REQUIREMENT to Control the Press using Gray Balance for G7. Heidelberg has Gray Balance Control on our Image Control and Axis Control products and this technology has been available for over 20 years now. Heidelberg Color Bars - or ANY OTHER COLOR BAR can be used to acheive G7 Objectives.

One very popular misconception that G7 Experts often proliferate is that the mid-tone value of 50%40%40% must be used for press control. Heidelberg has existing color bars that have 70%60%60% control patches that have been in use since the MID EIGHTIES. (we also have modified sets available with 50%40%40% patches if the customer insists) The point is that the 70%60%60% is a better value to use for press control than is the 50%40%40%. The reasons for this are many - but G7 Experts very often do not understand these parameters and tell Heidelberg Customers that they can't be Master Printer Qualified using the bars with 70%60%60% patches. THIS IS WRONG.

G7 Experts are often responsible for encouraging their customers to use Gray Balance as a Control Method with Specific "G7" color bars without having any practical experience in the methodology or any idea on how to implement it with Heidelberg Equipment. If Gray Balance Control isn't precisely implemented, press control becomes almost impossible. Even when properly implemented Gray Balance Control has very special considerations that are almost always ignored by G7 Experts.

Heidelberg has very important customers who print extremely high quality products who have attempted to use Gray Balance Press Control. After defining all of the necessary requirements for proper implementation almost all have concluded that using Gray Balance as a Press Control Method, while indeed very possible with Heidelberg Equipment, has it's own set of considerations which make it no more effective or accurate at controlling the printing process than Solid Ink Colors are.

Heidelberg is presently touring the US giving free informational seminars on how to Standardize, Optimize and Calibrate systems and equipment. We have had three testimonials from two differnt companies who have related their experiences with Heidelbergs Optimzation of their Systems and Implementation of G7 procedures. Both testemonials stated that the Heidelberg implementation of PCM (Print Color Management) has resulted in Extremely high operator confidence, extremely high customer satisfaction, and HUGE SAVINGS in LABOR and MATERIALS COSTS.

One customer related overall materials savings of 25% over a period of 6 months. They also related that when Heidelberg first came in to perform the service they were very skeptical because they had just gone through MONTHS of calibrating all presses and various substrates and screening systems to G7 using third party G7 Experts. Heidelberg came in - Standardized (to G7 Specifications), Optimized Press Settings and Calibrated Proof and Press Results and were completed with several presses and substrates in two days. (actually they stated that Calibrating to the G7 Specification took all of 10 minutes!!!

So, if you are a Heidelberg Customer you should consider having Heidelberg (teach you to) do all of your Optimization, Calibration and Standardization projects. If G7 Master Printer Qualification is your goal then Heidelberg Representatives are the best suited to help you in this process as well.

Please feel free to ontact me directly if any additional information is needed.

Very best regards,


Chuck Koehler
Heidelberg USA
1000 Gutenberg Drive
Kennesaw, GA 30144

[email protected]

 

[meddington]

The point is that the 70%60%60% is a better value to use for press control than is the 50%40%40%.

One reason I would prefer to have a 50, 40, 40 patch represented on the press sheet is that it is, generaly speaking, more visually and measurably comparable with other devices and processes than a 70, 60, 60. The dynamic range can differ from device to device, and certainly depending on different processes and consumables. Gray balance tends to taper toward whatever balance is inherent at 100, 100, 100 and gray compensation generally begins reduction around midtone. However, this is NOT to say that 70, 60, 60 shouldn't be used or is inferior for press control.

For Chuck's overlying point, consider G7 a tool in a tool box. If one were hiring a G7 consultant to qualify a proofing system, you'd generally want to find one with experience with that system rather than someone who would be seeing it for the first time.

 

[Chuck Koehler]

One reason I would prefer to have a 50, 40, 40 patch represented on the press sheet is that it is, generaly speaking, more visually and measurably comparable with other devices and processes than a 70, 60, 60. The dynamic range can differ from device to device, and certainly depending on different processes and consumables. Gray balance tends to taper toward whatever balance is inherent at 100, 100, 100 and gray compensation generally begins reduction around midtone. However, this is NOT to say that 70, 60, 60 shouldn't be used or is inferior for press control.

This is exactly what I am talking about.

There is a fundamental misconception about press control using gray balance and print monitoring with gray balance. Color Bars are for controlling the ink keys and if there are patches left over we can extract data from them as well. Color Bars on the tail edge of the sheet are very often distorted for a myriad of reasons making the gray patch values useless.

If you want to CONTROL a press with Gray Balance it is better to do so from the 3/4tone area because this is where the inking has the most effect on the Gray Curve just as is mentioned above. It is also where the interaction of the ink films, (trap) Ink and Water Balance, etc. are the most critical. Any gray compensation should not be applied to the color bar in any case.

If we assume (make something up) and we say that if adjusting the solid ink film from solid ink measurements happens at a 1 to 1 ration then we could say that adjusting the solid ink films based on gray values could happen at much higher ratios. The further down the Gray Scale that you attempt to control the higher the correction ratio becomes and the less accurate the follow ups will be.

It's harder to make mid-tone dots (or 40% dots) move than it is to make the 3/4 dots move when all you can adjust is solid ink.

As to MONITORING points, if you want to throw a 50%40%40% patch here and there on the color bar for that purpose that is great - go for it. Heidelberg would suggest to our customers that it is better to put those control marks somewhere more towards the center of the sheet where it is indicative of what is actually being printed. In fact Heidelberg's Image Control has a Mini Spot functionality that will measure those patches wherever they are on the sheet.

If the system is well calibrated, and the calibrated results of the 70%60%60% area are used as target values then Gray Balance may work just as good as solid ink for press control. If arbitrary reference values for Gray Balance are used as published in some document or guide without concern to what is actually acheivable, then very likely a disaster will occur trying to control the press to those values, which is what is very common after a G7 Expert has been to a Heidelberg customer.

I could go on and on and on about all of the ramifications of controlling via Gray Balance, but the bottom line is that Controlling the Press using Gray Balance and using any particular color bar are NOT REQUIREMENTS OF G7.

For Chuck's overlying point, consider G7 a tool in a tool box. If one were hiring a G7 consultant to qualify a proofing system, you'd generally want to find one with experience with that system rather than someone who would be seeing it for the first time.

Very true. Although it is stated many times people do not tend to think that G7 is a procedure. People generally mistake G7 for a Standard. We all know that is not the case, but that is the prevailing confusion.

What makes matters extremely confusing is that G7 can be accomplished using processes other than G7. (often with better results) Technically and literally speaking G7 can only be done with the Graph Paper or the IDEAlink Curve Software. Everyone interprets this differently and they use the confusion to implement whatever process they feel is appropriate and they call it G7. Others have painstakenly tried to avoid even mentioning G7 because it is in fact a very specific procedure when done by the book.

The majority of G7 Experts use the procedures that they feel comfortable with to acheive the intended results of G7 and they call it G7. Technically this is wrong, but practically it acheives the desired result. This confusion gives license to anyone to iterpret their solution as G7 while at the same time claiming that other solutions are not G7.

When all is said and done if you want to acheive the best possible G7 results with Heidelberg Products you will be best served to have Heidelberg implement the required procedures and train your employees how to utilize the technology to maintain it!


Regards,

Chuck Koehler
Heidelberg
Prinect Color Specialist

 

[Chuck Koehler]

Heidelberg CAN

Heidelberg CAN

By the way, in response to the original post by prepressguru:

We aiming to get our G7 certificate. Currently we have invested in Heidelberg Image control and Color Tools. Which I find to be a great set of hardware and software. Been through the training and matched our proof to press, and calibrated to near neutral. Recently had a visit by a service group which helps with G7 certification. To me it looks like the steps I have learned from Heidelberg are very much the same. I suggested we run the G7 form without their help then submit it.

This illustrates my point exactly:

Service group enters Heidelberg Printer after Heidelberg has set them up to G7 using Heidelberg Solutions.

Service group repeats very similar procedure and ends up with same results.

Confusion allows for Service group to WRONGLY claim that they are the only ones that can Qualify Master Status because Heidelberg system is not G7.

Customer satisfied with Heidelbergs (very probably better results) but are told that G7 wasn't followed so Master Status can't be granted even though desired results are obtained and people understand the procedures and can repeat them.

HEIDELBERG SOLUTIONS ARE RECOGNIZED BY IDEALLIANCE AS G7 SUPPORT TOOLS AND CAN BE UTILIZED TO GAIN MASTER PRINTER QUALIFICATION. HEIDELBERG HAS G7 CERTIFIED EXPERTS THAT CAN QUALIFY HEIDELBERG CUSTOMERS AS G7 MASTER PRINTERS. HEIDELBERG HAS COMPLETE SOLUTION FOR G7 IF THAT IS WHAT PRINTER WANTS TO DO.

 

[joecloutier]

Chuck,

Nice job explaining and clarifying the benefits of using trained Heidelberg PCM specialists and the tools available to Heidelberg customers

 

[Chuck Koehler]

Joe,


Thanks - Chuck

 

[prepressguru]

Yes we want to get our G7 master Printer Qualification, from the doc you sent (thanks) I just need a G7 Expert to ok the sheet for me. Which is what I am planning to do since I have the training and equipment from Heidelberg.

You're referring to G7 Master Printer Qualification (not certification) status, correct? Per Idealliance, Master Printer Qualification must be performed by a certified G7 Expert.

 

[prepressguru]

Hi Chuck thanks for responding to my question, I was wondering when you would =)

Great posts... all of them. It looks like I have the correct tools and knowledge. Since Heidelberg can approve my G7 requirement I will be going that route. Chuck I will PM you on this as I do have a question.

1 interesting point I will throw in. When I did meet with this G7 service team the mentioned how desginers could purchase a G7 approved desktop printer for a few hundred dollars and expect them to match to press. I dunno I was not impressed by this.

Thanks!

By the way, in response to the original post by prepressguru:




This illustrates my point exactly:

Service group enters Heidelberg Printer after Heidelberg has set them up to G7 using Heidelberg Solutions.

Service group repeats very similar procedure and ends up with same results.

Confusion allows for Service group to WRONGLY claim that they are the only ones that can Qualify Master Status because Heidelberg system is not G7.

Customer satisfied with Heidelbergs (very probably better results) but are told that G7 wasn't followed so Master Status can't be granted even though desired results are obtained and people understand the procedures and can repeat them.

HEIDELBERG SOLUTIONS ARE RECOGNIZED BY IDEALLIANCE AS G7 SUPPORT TOOLS AND CAN BE UTILIZED TO GAIN MASTER PRINTER QUALIFICATION. HEIDELBERG HAS G7 CERTIFIED EXPERTS THAT CAN QUALIFY HEIDELBERG CUSTOMERS AS G7 MASTER PRINTERS. HEIDELBERG HAS COMPLETE SOLUTION FOR G7 IF THAT IS WHAT PRINTER WANTS TO DO.

 

[meddington]

. Any gray compensation should not be applied to the color bar in any case.

Hi Chuck, can you explain the perceived benefit of using an "uncompensated" colorbar? My opinion has always been that the colorbar should represent the same screening and curve compensation as the imagery (less any color transforms), unless the particular press control solution requires something else . For instance, would you recommend a "linear" AM colorbar for gray compensated, stochatic imagery?
Gray balance could conceivably be different for the above.

Mike

 

[Chuck Koehler]

Gray Compensation in the Color Bar

Gray Compensation in the Color Bar

Gray balance tends to taper toward whatever balance is inherent at 100, 100, 100 and gray compensation generally begins reduction around midtone.

Hi Mike,

First and foremost I never recommended using "Uncompensated" Color Bars. Color Bars should have whatever CALIBRATION Curve that you are using applied to it. They should also use the same screening parameters that are being applied to the work.

As far as ANY kind of Color Transformation or Separation that should not be applied. Gray Compensation is a Color Transformation or Separation component and should never be applied to the color bar - especially if you are going to use that color bar to control the press.

The Color Bar is a MECHANICAL Tool for controlling individual units of a press. It is for controlling Ink Film Thicknesses. Color Bars are not really meant for Color Analysis. We can include other targets to the press sheet if we want to do Color Analysis. To perform Color Analysis on the production sheets control items should have the Color Transforms applied to them.

Trying to use the Color Bar for Color Analysis is very limited. The only thing that can accurately be monitored from the Color Bar are Solids and Overprints. Dot Gains can be monitored, but even this can be tricky if the color bar is at the tail of the sheet. Gray Balance is the most difficult thing to monitor from a color bar on the tail of a sheet. Sheet Movement, Press Speed, Spray Powder (if the sheets are going through a second time), Sheet Fan Out, Sheet Slap or scuffing, Ink Build Up on Blankets, Dot Gain, Three Color Trap Characteristics, Register, Proceding from Make-ready to Production all (and more)affect the Gray Balance.

While the actual work may have Color Transforms applied, the job of the Color Bar is to Control the press. Even though in the actual production work the 70% Cyan, 60% Magenta and 60% Yellow will most likely be somewhat reduced with an additional Black Component added that doesn't mean that we shouldn't use those values (with same curve bot no transformation) to maintain stability in the inking with reference to Grays. The further towards the Highlight that you choose to try and Control Gray Values the more the Control System will overcompensate.

 

[Chuck Koehler]

Hi Prepress Guru,

I feel your pain! That is the line being sold to the designers and print buyers. Have your printer (Epson, Canon, etc.) G7 Certified and then the Pressroom can match it if they are G7.

I recently helped a printer with their calibration to G7 and if I heard once from the Head of Prepress I heard 30 times that the press needed to match their G7 Certified Proof. I listened politely but told them that we needed to continue to calibrate press results directly to the GRACoL Profile. After the press was done the match was extremely close to their proof except in the 1/4 tones.

The Head of Prepress noted that the match was considerably off in the 1/4 tones and said that the plates would have to be color managed to match their G7 Certified Proof.

I then opened the results in Prinect Quality Monitor and within roughly 1 minute discovered the issue. Their G7 Certified Proof had a 10% bump in the 1/4 tones to match whatever substrate they used to calibrate with in the past. It was way off, but all of the requirements for G7 Certification had been met!

I am not trying to say that G7 Certification is a bad thing, but it supports my observation that it is not the certification but the different interpretations that have been allowed to proliferate unchecked that cause the problems. Companies get their employees G7 Expert titles and then send them out to the printers to give the service away for free as support for whatever product they are selling. Of course, if you own an ACME Printer and the ACME company gets you a G7 Master Qualification for free why not? I'll bet that there will never be a problem with the ACME Printer Results!!

And - did you know - that G7 Master Qualification has little if anything to do with the actual results that are obtained? There are no tolerances in place as of yet to fully quantify results. The G7 Master Status is granted to Companies for their understanding of the G7 Procedures. It is more or less proof that you were "trained" by a G7 Expert. "Trained" is in quotes because when the ACME company does your G7 work for free they very rarely train you, but instead they set it up as a service that they will perform for you.

Heidelberg has Solutions and we TRAIN you in those solutions. But much more than that Heidelberg TRAINS you in the Solution throughout your production workflow - from Prepress - to Proofs - to Plates - to Press Optimizations - to Quality Monitoring and Verification.

CK

 

[meddington]

First and foremost I never recommended using "Uncompensated" Color Bars.

Nope, you didn't. My bad.

Color Bars should have whatever CALIBRATION Curve that you are using applied to it. They should also use the same screening parameters that are being applied to the work.

Agreed.

Gray Compensation is a Color Transformation or Separation component and should never be applied to the color bar - especially if you are going to use that color bar to control the press.

When I mentioned to "transformation", I was referring to an icc/device- link conversion, which of course you'd want to avoid on the press control elements. Afterall, you wouldn't want impurities on the solids or tints on your colorbar. A plate compensation/calibration curve I take to refer to a 2 dimensional adjustment at the rip level toward target tonality, (either defined by tvi or NPDC, which could include an adjustment for gray balance if desired) . This accomplished by adjustment in dot percent of process channels individually, or in tandem.

As far as applying to a colorbar, I see little difference between adjusting individual channels toward target tvi and adjusting individual channels toward an NPDC, including gray balance. If magenta were adjusted (via rip curves) 3% lower at midtone to hit the target tvi, this would of course effect gray balance, but I don't know that if go so far as to call it a "color transformation". Would it be your opinion that adjustments for tvi should not be applied to the colorbar as well?

Your comments on the difficulties of monitoring gray balance are correct. However, it has not been my experience that gray balance is blatantly misleading from the vantage point of the colorbar. By this I mean that I (generally) don't see significant differences between gray patches at the gripper or tail and those located in the center of the sheet. I would also state that the large majority of "visual matches" to supplied proofs I review occur when solid inking and 50C, 40MY patches are very close to target aims. I should point out that our plant is not closed loop, and the primary metric is solid inking, with gray balance as a monitoring metric.

Thanks for the discussion.
Mike

 

[Chuck Koehler]

Hi Mike,

Sorry for the confusion - I don't know how to say it clearer. Here is what I stated earlier:

Color Bars should have whatever CALIBRATION Curve that you are using applied to it. They should also use the same screening parameters that are being applied to the work.

Calibration Curves should compensate for Tonality and Gray Balance in my opinion. The calibration curve adjusts for Gray but is short of Gray Compensation which is done via some form of transformation. What I think is being confused is the following:

Gray Compensation is a Color Transformation or Separation component and should never be applied to the color bar - especially if you are going to use that color bar to control the press.

But I clearly differentiate or explain that I feel that a Gray Compensation is a "color transformation". In my opinion a transformation of any kind is done via a profile.

As far as applying to a colorbar, I see little difference between adjusting individual channels toward target tvi and adjusting individual channels toward an NPDC, including gray balance. If magenta were adjusted (via rip curves) 3% lower at midtone to hit the target tvi, this would of course effect gray balance, but I don't know that if go so far as to call it a "color transformation". Would it be your opinion that adjustments for tvi should not be applied to the colorbar as well?

You are correct. Nope, TVI or Near Neutral Curves or whatever Calibration Curves should be applied to the Color Bar.

However, it has not been my experience that gray balance is blatantly misleading from the vantage point of the colorbar. By this I mean that I (generally) don't see significant differences between gray patches at the gripper or tail and those located in the center of the sheet. I would also state that the large majority of "visual matches" to supplied proofs I review occur when solid inking and 50C, 40MY patches are very close to target aims. I should point out that our plant is not closed loop, and the primary metric is solid inking, with gray balance as a monitoring metric.

Perfect! You have just explained very clearly my point of differentiating between Controlling using the color bar and Monitoring using the color bar.

In your plant the control is solid inking. That is the metric that allows you to maintain consistency and it produces a consistent Gray Value. I stated awile ago that if we assume that Solid Ink Control happens at a 1 to 1 ration then Gray Balance Control affects the Solids at a much higher ratio (1 Gray Value = 5 Solid Ink Vales)

With a Closed Loop System (or even with Handhelds) when the Solid Ink chages .05 Density it is compensated for to keep the print characteristic as stable as possible. I wouldn't say that a .05 Density Shift is that objectionable - if you can even see it, but we compensate for it to keep the system as stable as possible so that it doesn't continue to a .10 Density difference. This can be done via Handheld or Closed Loop.

With Gray the equivalent to a .05 Densithy Shift may be a .5 Delta E? The Closed loop system attempts to compensate for the fluctuation and changes the inking accordingly. Now to get the correction necessary to compensate for the .5 Delta E the Solid is moved to a more drastic degree, lets just say .10 density. Gray is good but Solids start to become less controllable. These small deviations in gray values occur for all of the reasons I listed in one of my previous posts.

The issue becomes that the operator really doesn't know how to react to the .5 Delta E shift, and the visual result isn't that objectionable so they don't make the move. They do detect the .05 Density Shift and compensate for it correctly. The Gray Value gets better but it is not 100% perfect.

The automated system, doing it's job very well, corrects precisely for the .5 Delta E error and starts the system into a less controllable cycle, but the Gray Value is right on - for the next pull or so.

Again, I will mention that if all is set up correctly Gray Control can work very well. To say that it works 50% - 25% - 10% - or even 5% better than Solid Ink Control would be a stretch. So, in other words after you have jumped through all of the hoops required to get Gray Control set up to optimum conditions, it is equally as good as Solid Ink Control that didn't require any Hoop Jumping.

Chuck

 

[meddington]

By George I think we're in complete agreement in your last post!

Thanks for clarifying. Sometimes it takes several days and multiple posts to clarify points that would take mere seconds in the course of normal conversation.

Best,
Mike

 

[prepressguru]

Chuck, I sent you a PM, can you let me know?

 

[wordtothis]

-If I may, this is an awesome thread to read...