How to handle the G7 compensation curve with scheduling of production

[Bloodsaler]

I have been bothered by this question for long.
Suppose we have 4 presses,each press has done a G7 test serprately,that means each press have its own compensation curve.
But our production schedule are full,so the real situation is we can`t manage all the jobs in a certain press,it may changed in some circumstance.That means we do our prepress for one press compensation curve,but suddenly this job need to move to another press,but the platemaking almost done.All we have to do is replatemaking another set of plates for the other press,but in this process,the time will be wasted.And it may delaying the delivery.
So I want to know guys,what you will do when you meet this situation?

 

[meddington]

Not many great options...either re-plate with custom curves, use a generic curve for all plates and deal with the inherent differences between the presses, or nail down scheduling so that you avoid last minute re-routing of jobs and do just-in-time plating. If the tonal differences between presses were different enough to warrant custom plate curves, then you have a trade off and have to look at what's costing you more money. Luckily with CTP the plating stage can go pretty quick.

 

[TerryWyse]

Been there....done that.....only I'm the guy making the G7 curves for a customer....and this problem comes up occasionally where they purposely have "identical" presses so they can exchange plates.

First thing, get all the presses printing identically as much as you can. Fix the mechanical issues first and then simply make sure that you're using all the same consumables (ink, blankets, fountain solution) and that each press crew is preparing the press IDENTICALLY in terms of chemistry, pressures, packing, etc.

If it were me being given this task, I'd run an initial calibration run (linear) on each press and see where they're all printing relative to each other. It's obviously important the same aimpoints be used when you do this (insert shameless plug for SpotOn! software here). Once you do that, you should have a good picture of what's going with each press relative to the others...or the average. If you see that 3 out of 4 are close, average those presses together and come up with a common curve. The one press that's out, either do a custom curve for that one press or simply note how this press prints relative to the others and see if you can fix it or use the common curve and accept the difference. Usually the average curve of 2 or more presses is close enough that a slight push/pull of the densities is all you need to get a reasonable match between them.

My (G)7 cents worth.

Terry

 

[Bloodsaler]

Thanks guys,your advises I have considered,but doing all the presses calibrated need a long time,but during the calibration time,I may have to ensure the calibrated one printed great gray balance,and this conflict with production schedule~
I have no other great idea than yours,but some of my presses are komori,some are heidelberg,some are KBA,may make every press in a same condition harder?

 

[David Milisock]

Thanks guys,your advises I have considered,but doing all the presses calibrated need a long time,but during the calibration time,I may have to ensure the calibrated one printed great gray balance,and this conflict with production schedule~
I have no other great idea than yours,but some of my presses are komori,some are heidelberg,some are KBA,may make every press in a same condition harder?

Unfortunately no matter what calibration process you use the solution would be to invest some time into researching redundant and or a single faster plate setting solution. This is an expensive solution.

 

[tmiller_iluvprinting]

Unfortunately no matter what calibration process you use the solution would be to invest some time into researching redundant and or a single faster plate setting solution. This is an expensive solution.

Geez Dave-I don't see how a faster plate setter is going to help find harmony between presses from 3 different manufacturers. Are you sure you are answering the original post, or are you confused with another?

Regards,
Todd

 

[David Milisock]

Geez Dave-I don't see how a faster plate setter is going to help find harmony between presses from 3 different manufacturers. Are you sure you are answering the original post, or are you confused with another?

Regards,
Todd

No it's not but since there is no answer to that issue he can use faster or multiple plate setters andwait to plat euntilthe last moment.
The newer plate on demand systems may be of some asistance there btu as i said this could be big bucks

 

[tmiller_iluvprinting]

No it's not but since there is no answer to that issue he can use faster or multiple plate setters andwait to plat euntilthe last moment.
The newer plate on demand systems may be of some asistance there btu as i said this could be big bucks

There is an answer to the original question and Mike And Terry have more than covered it. I would like to suggest to you that we leave the advice to the true color management professionals, and to those that truly understand the world of print.
To the rest I say "Beware false prophets!"

Regards,
Todd

 

[David Milisock]

There is an answer to the original question and Mike And Terry have more than covered it. I would like to suggest to you that we leave the advice to the true color management professionals, and to those that truly understand the world of print.
To the rest I say "Beware false prophets!"

Regards,
Todd

No what he got was a bunch of his and that, curves that will vary as the press ages and one universal curve that won't last a month after it's made. Each press is different, plate at the last minute to the destinatiin press. Unfortunately this guy has to make money he'll spend more then he'll make on 20 jobs doning anything less. Used plate setters are getting cheaper right now.

Presses are fluid, a thoudsnd things vary and change that's why I lienerize and use PS management.

 

[meddington]

I've got plate curves that were created in 2005 and 2007 still in use and still valid. Just sayin'

 

[David Milisock]

I've got plate curves that were created in 2005 and 2007 still in use and still valid. Just sayin'

I'm not surprised, well maintained systems do much better then those left unattended, or those attended by lesser technicians. The question is what is valid?

My question as i read the Gracol Seven and the G7 specification is where is Gods name are they inserting these changes? It has to pre or post plate setter.

I was reading the G7 specs last night and just got caught up in the BAIN of Printing, Wet trapping. If they think wet trapping is an issue wait until they tray and dry trap 4 color process on a thin coated text!!

Some of the stuff was as if they had never ran a press.

I'm going to read the full Gracol Seven Spec for fun.

 

[meddington]

The G7 methodology is "process agnostic", but assuming the process has a plating stage, as does offset litho, this would be the logical area to apply compensation...not sure how you would achieve anything post plating.

Btw, there were quite a few very experienced professionals involved in the development of and/or providing input for the Gracol spec and G7 methodology, more than a few with ink under their nails.

 

[tmiller_iluvprinting]

Now he's questioning the G7 authors!

Now he's questioning the G7 authors!

I need to ask Dave, how many impressions have you run on press? Don't read the GRACol and G7 papers for fun, read them to get your crap straight and then come back and maybe you just might have some understanding of what we are doing here. In the meantime, as I stated before, leave the color management to those who know color management, and quit wasting time.

Regards,
Todd

 

[David Milisock]

The G7 methodology is "process agnostic", but assuming the process has a plating stage, as does offset litho, this would be the logical area to apply compensation...not sure how you would achieve anything post plating.

Btw, there were quite a few very experienced professionals involved in the development of and/or providing input for the Gracol spec and G7 methodology, more than a few with ink under their nails.

I'm just getting over bronchial pneumonia and will be catching up and then plan on some reading. I'm downloading the specs and the directions and will give then a read it's only a few bucks. I will tell you this having read part of the specs and some of their statements I'm wondering just WTF these people are thinking but lets hold off until I have a chance to see the entire picture.

Giving the historical relationship between this industry and technology I'm not holding my breath. Lets face it I would like to see if running a process in January when the pressroom is at 10% humidity and 76 degrees has any validity in August when its 95% humidity and 96degrees.

No one believe in systemic processes like color management more than me but for my money I'll take the long rout ans seperate the wheatfrom the chafe first.

 

[TerryWyse]

No what he got was a bunch of his and that, curves that will vary as the press ages and one universal curve that won't last a month after it's made. Each press is different, plate at the last minute to the destinatiin press. Unfortunately this guy has to make money he'll spend more then he'll make on 20 jobs doning anything less. Used plate setters are getting cheaper right now.

Presses are fluid, a thoudsnd things vary and change that's why I lienerize and use PS management.

I honestly have trouble trying to follow your line of thought...could be that I just don't "get" what you're trying to say.

To say "presses are fluid, a thoudsnd [sic] things vary..." is simply stating the obvious and not helpful. Of course presses are variable and of course we linearize are plates or have other QC measures in place to try and minimize variables where we can.....press/plate calibration being one of those measures to at least help quantify this variability. Given that variability is a fact of life in the pressroom, what are you suggesting as an alternative...doing nothing? The variability is going to be there regardless whether you do nothing, employ a press calibration method such as G7 or go full (PS?) color management. Really, the methodology (or not) is quite a different topic than doing what we can to reduce variability in the pressroom. Point is, I think we all understand that variability is there (in the pressroom) and that it must be dealt with before ANY (or none) solution is proposed or advocated....no method is a silver bullet to reducing or eliminating pressroom variables.


But I digress....

I want to touch on something that you seem to mention often...."PS color management". To myself and perhaps many of us, this conjures up visions of in-RIP color management using CRDs and CSAs...basically a non-ICC approach where the Postscript Interpreter (aka "RIP") is handling color conversions internally.

Is this what you're suggesting and advocating as a viable CM workflow for offset printing or even digital printing? Please clarify if you could...perhaps I'm misunderstanding your use of the term "PS color management" in this post and a few others.

Terry

 

[TerryWyse]

Giving the historical relationship between this industry and technology I'm not holding my breath. Lets face it I would like to see if running a process in January when the pressroom is at 10% humidity and 76 degrees has any validity in August when its 95% humidity and 96degrees.

Then I would suggest you're completely mis-interpreting what the G7 method is all about...or really what any "calibration" method is all about, be it G7, System Brunner, TVI methods or Color Management in all it's permutations.

In my opinion, calibration methodologies are a first step towards defining what the *target* printing condition should be......color management might target a specific colorimetric data set while something like G7 is a bit looser and defines a target density tone curve and target gray balance and leaves colorimetry as a secondary but (possibly) related metric.

In any case, defining what the target is...is the first step towards eliminating variability. Once you know what the target printing condition SHOULD be, you can then take steps to quantify what sort of variability you have and what can be done to reduce it (eliminating variation is impossible). Since eliminating all variables is impossible or at leas timpractical, you then must decide what are acceptable tolerances for your customers and target market. While the calibration methodology doesn't exist to eliminate variability, quite often the methodology will suggest tolerances to help guide you in that direction.

Nobody here (I think) is suggesting that a particular calibration methodology alone is going to reduce variability...it's there, at least partially, to help reveal where there is variability in your process. The G7 methodology is neither a humidifier nor a temperature control system.

Terry

 

[David Milisock]

I honestly have trouble trying to follow your line of thought...could be that I just don't "get" what you're trying to say.

To say "presses are fluid, a thoudsnd [sic] things vary..." is simply stating the obvious and not helpful. Of course presses are variable and of course we linearize are plates or have other QC measures in place to try and minimize variables where we can.....press/plate calibration being one of those measures to at least help quantify this variability. Given that variability is a fact of life in the pressroom, what are you suggesting as an alternative...doing nothing? The variability is going to be there regardless whether you do nothing, employ a press calibration method such as G7 or go full (PS?) color management. Really, the methodology (or not) is quite a different topic than doing what we can to reduce variability in the pressroom. Point is, I think we all understand that variability is there (in the pressroom) and that it must be dealt with before ANY (or none) solution is proposed or advocated....no method is a silver bullet to reducing or eliminating pressroom variables.


But I digress....

I want to touch on something that you seem to mention often...."PS color management". To myself and perhaps many of us, this conjures up visions of in-RIP color management using CRDs and CSAs...basically a non-ICC approach where the Postscript Interpreter (aka "RIP") is handling color conversions internally.

Is this what you're suggesting and advocating as a viable CM workflow for offset printing or even digital printing? Please clarify if you could...perhaps I'm misunderstanding your use of the term "PS color management" in this post and a few others.

Terry

First postscript color management IS NOT VIABLE for any digital work flow that is purely designed for ICC control such a a Kodak Nextpress , Xerox IGen, Cannon ECT. and Ink jet work flows such as Onyx Postershop and others as these device are designed as ICC controlled only and fully capable of native color conversion to their media profile. I.E. they can take RGB, spot color, grayscale and CMYK and convert to the media profile VIA an ICC controlled process.

Press RIPS can be another issue, the final conversion of any color and this should be CMYK to CMYK is to their media, (the plate) which of course specialized to function on a particular paper and press under specific ambient working conditions.

Now all of the devices I've used allow the use of ICC profiles before the final stage of plate setting but the META, Rampage and Harlequin systems I've just been on are all PS color managed at this point. I will be on an Apogee System next week and check but if memory serves it's also PS color managed.

Now anyone with any experience knows that PS color managed systems simply connect two CMYK color spaces and modify only the color outside the destination based on density . So basically the gray balance going in is the gray balance going out so color control is application based in the customer controlled via ICC and press is PS.

In this situation if you interject an ICC profile before the plating you're changing the customers color. However the end process is still PS color managed.

If you interject an ICC process during the plate setting this will leave the customers color unchanged however you then have to over ride all the manufactures settings and create a linearizion dot gain calibration that's ICC controlled.

Of all the press systems I've worked on all of the final processes are PS color managed. Hey I'm willing to learn a new process but let's see it defined properly first. Does this system change the customers color or does it not change the customers color? If not then how does it interface with the plate setter and create the media linearizion?

I'll download the instructions and take a look, it shouldn't be too hard to sort out the truth to how it really works.

 

[TerryWyse]

Now all of the devices I've used allow the use of ICC profiles before the final stage of plate setting but the META, Rampage and Harlequin systems I've just been on are all PS color managed at this point. I will be on an Apogee System next week and check but if memory serves it's also PS color managed..

With regards to RAMpage, nope, you're wrong. RAMpage does indeed allow for "PS" or in-RIP color management via hooks into it's Harlequin PS interpreter...but using this method for performing color transforms would be atypical for a RAMpage end-user. Not saying it's good or bad, just different. Usually the in-RIP color management is reserved for doing RGB-to-CMYK transforms only.

But RAMpage does indeed have a feature for applying an ICC transform POST-RIP and PRE-platesetter...the option is called INKdrop and it's used primarily for applying an ICC device link transform but you can also apply a standard (CMYK-to-CMYK only) ICC transform as well. Point is, this transform is taking place on RAMpage's native raster data (no PS "interpretaton" as all elements have been rasterized) and can take place just prior to plate imaging.

Now anyone with any experience knows that PS color managed systems simply connect two CMYK color spaces and modify only the color outside the destination based on density . So basically the gray balance going in is the gray balance going out so color control is application based in the customer controlled via ICC and press is PS.

I honestly have NO IDEA what you just said but it sounds wrong.......you're saying a CMYK-to-CMYK transform based on *density*? Gray balance going in/out is the same? Even a *curve* transform will modify the input/output gray balance let alone a transform between two CMYK color spaces, regardless if it's ICC or PS color management. (just to clarify (again), by "PS" you mean Postscript and not Photoshop?)

If you interject an ICC process during the plate setting this will leave the customers color unchanged however you then have to over ride all the manufactures settings and create a linearizion dot gain calibration that's ICC controlled.

Now I'm lost again....the ICC "process" leaves the color unchanged?.....and you have to create a linearization dot gain calibration that's ICC controlled?
1) an ICC transform will virtually ALWAYS change the resutling separation, even if you're using the same profile as both source and destination and 2) I've never seen a "linearization dot gain calibration" that was ICC controlled with the rare exception of embedding a calibration curve inside a device link profile (Alwan LinkProfiler). Seriously, I have no idea what you're trying to communicate here but much if it sounds backwards to me.

Of all the press systems I've worked on all of the final processes are PS color managed.

You should get out more often.

Hey I'm willing to learn a new process but let's see it defined properly first. Does this system change the customers color or does it not change the customers color? If not then how does it interface with the plate setter and create the media linearizion?

Define "changes the customer's color"? If you mean "does it change the customer's original CMYK separation values to something different", of course it does....that's the idea! If you mean does it change the *appearance* of color, that's a different question. I would say it changes the CMYK values to meet the customer's expectation of color (hopefully)....this is true of an ICC transform or simple plate curves....BOTH change the customer's original separation values but with the intent to preserve the expected color appearance.

How does it interface with the platesetter and create the media linearization? If you're speaking specifically of the G7 method, it really doesn't "interface" with the platesetter ("process agnostic" as Mike Eddington would say). The G7 method will create/suggest certain plate curve corrections....HOW they are applied is workflow/system specific and outside of the G7 process itself. In fact, with most systems the curve corrections can be applied in many different ways and even in different parts of the workflow....G7 does not dictate in any way HOW it's calibration curves are used or even WHERE they are used, it's simply saying "these are the input/output curve corrections that need to be on the plate media"...period. I think you're confusing the G7 method with some sort of "system" as opposed to simply a technique that's used to aid press calibration.

I suggest you read the full G7 "How-To" docs...maybe read it a couple of times for it to sink in....and then come back with more questions. If you've got any output devices at your disposal, even an inkjet printer, you could try using the "fan graph" method for doing a G7 calibration just to get the feel of it. I think that will go a long way towards clearing up any confusion you may have.

Terry

 

[David Milisock]

With regards to RAMpage, nope, you're wrong. RAMpage does indeed allow for "PS" or in-RIP color management via hooks into it's Harlequin PS interpreter...but using this method for performing color transforms would be atypical for a RAMpage end-user. Not saying it's good or bad, just different. Usually the in-RIP color management is reserved for doing RGB-to-CMYK transforms only.

But RAMpage does indeed have a feature for applying an ICC transform POST-RIP and PRE-platesetter...the option is called INKdrop and it's used primarily for applying an ICC device link transform but you can also apply a standard (CMYK-to-CMYK only) ICC transform as well. Point is, this transform is taking place on RAMpage's native raster data (no PS "interpretaton" as all elements have been rasterized) and can take place just prior to plate imaging.




I honestly have NO IDEA what you just said but it sounds wrong.......you're saying a CMYK-to-CMYK transform based on *density*? Gray balance going in/out is the same? Even a *curve* transform will modify the input/output gray balance let alone a transform between two CMYK color spaces, regardless if it's ICC or PS color management. (just to clarify (again), by "PS" you mean Postscript and not Photoshop?)




Now I'm lost again....the ICC "process" leaves the color unchanged?.....and you have to create a linearization dot gain calibration that's ICC controlled?
1) an ICC transform will virtually ALWAYS change the resutling separation, even if you're using the same profile as both source and destination and 2) I've never seen a "linearization dot gain calibration" that was ICC controlled with the rare exception of embedding a calibration curve inside a device link profile (Alwan LinkProfiler). Seriously, I have no idea what you're trying to communicate here but much if it sounds backwards to me.



You should get out more often.



Define "changes the customer's color"? If you mean "does it change the customer's original CMYK separation values to something different", of course it does....that's the idea! If you mean does it change the *appearance* of color, that's a different question. I would say it changes the CMYK values to meet the customer's expectation of color (hopefully)....this is true of an ICC transform or simple plate curves....BOTH change the customer's original separation values but with the intent to preserve the expected color appearance.

How does it interface with the platesetter and create the media linearization? If you're speaking specifically of the G7 method, it really doesn't "interface" with the platesetter ("process agnostic" as Mike Eddington would say). The G7 method will create/suggest certain plate curve corrections....HOW they are applied is workflow/system specific and outside of the G7 process itself. In fact, with most systems the curve corrections can be applied in many different ways and even in different parts of the workflow....G7 does not dictate in any way HOW it's calibration curves are used or even WHERE they are used, it's simply saying "these are the input/output curve corrections that need to be on the plate media"...period. I think you're confusing the G7 method with some sort of "system" as opposed to simply a technique that's used to aid press calibration.

I suggest you read the full G7 "How-To" docs...maybe read it a couple of times for it to sink in....and then come back with more questions. If you've got any output devices at your disposal, even an inkjet printer, you could try using the "fan graph" method for doing a G7 calibration just to get the feel of it. I think that will go a long way towards clearing up any confusion you may have.

Terry

You seem to be stuck in some kind of ICC mind set so let's try this with a black box theory method, forget everyhting you've ever known about ICC profiles we're in the days before ICC profiles

Applications , MS, Adobe, Corel what ever call this (process 1) creates a file that has a CMYK color space A.

The RIP/Setter combination through a series of calibrations and internal software prosesses, (process 2) work in conjunction to create CMYK color space B (the press destination)

This is postscript color management as it was then and is now for every plate setter I've seen.

So the questions are
1. Is this G7 Swop or what ever ICC controlled process inserted in the application (process 1) changing color space A?

2. Is this process inserted between process 1 and process 2, now converting color space A and making a new color space A?

3. Is this process used in replacing the internal RIP/Setter process creating a true ICC controlled destination CMYK color space B?

4. Is this process inserted after process 2, simply creating a changed color space B?

Now if we're talking #3 above I'm all for giving it a shot sounds interesting. If we're talking #1 so what, but #2 and #4 are a waste of time it's just PS color management with a profile attached.

I can see where it would be well used in scenario #3 and #1 setting the creation applications to work in the destination space.

Don't sweat not getting PS color management Fraser, Murphy and Bunting didin't get it either. They had the basics but failed to understand that at the time their book was written every device manufacturer created a PS or EPS plug in for Quark because Quark didin't create an Adobe conforming PS file.

 

[TerryWyse]

You seem to be stuck in some kind of ICC mind set so let's try this with a black box theory method, forget everyhting you've ever known about ICC profiles we're in the days before ICC profiles

Applications , MS, Adobe, Corel what ever call this (process 1) creates a file that has a CMYK color space A.

The RIP/Setter combination through a series of calibrations and internal software prosesses, (process 2) work in conjunction to create CMYK color space B (the press destination)

This is postscript color management as it was then and is now for every plate setter I've seen.

On the other hand...I've not been to a shop yet that's using Postscript color management to drive their platesetter. Frankly, I thought PS color management died a long time ago and was effectively replaced by tagged PDF workflows. Different strokes I guess.

"...through a series of calibrations and internal software prosesses [sic]..." ?
Sounds good....but doesn't give me much to go on.

And, yes, I have an ICC mindset....it's my job.

I guess at this point we're just talking past each other David......but I would like to hear the answer to a question that's been asked of you a couple of times without an answer that I'm aware of: when you say "linearize a press", do you mean an original 50% value in the file prints and measures as a 50% dot on paper? I would really like to get a direct answer to that question....a 50% dot printing as 50% on paper is an interesting concept that I would like to hear more about.

Terry