Fingerprinting Suggestions

[dimitri]

What paper types do you refer to? There are lots used in packaging.

You do not really care about your stock itself, but you care about the expected color of your solids and overprints on that stock if you want to hit GRACOL/ISO values. I say you do not care about the color of your stock itself, because as already mentioned, G7 would through you on the grey if you follow the methodology regardless of stock. TVI should do something similar.

But, the color of your solids could be affected by the color (and absorption properties) of the stock. So, if it is SBS stocks, you should be fairly close on grade 3, and for color close to the SWOP2006 Coated3 or even GRACoL2006 Coated1 profiles. Check it out. The color of that stock is grade 3, but you should be able to hit the solids referenced for grade 1 as well. For uncoated stock (USBS), you should be close to grade #5 or SWOP2006 Coated5 profile for color.

 

[Retroman]

Very good point...I highly agree!

Just some food for thought:

The consortium is either in a state of confusion, or they are missing some information on what really goes on in the press room. I suspect a lot of the comments I'm reading are coming from pre press oriented folks that don't understand the full complexity of a printing press.

There are rules for creating and manufacturing saleable color. It's really quite simple.
Never show a client a proof that does not represent the true structure of the data files. In other words, make certain that your proof is a true color representation of the final files. Blindly following the edicts of a consortium of industry "experts" will get you nothing but heart aches. It does nothing towards educating you or your staff. The expert arrives on site, makes a series of tests, provides a few "fixes" and leaves again. In the following months things start to drift and Bingo you're right back where you started; press doesn't match the proof.

What to do? Apply some conventional wisdom that has worked for generations of printers.

Step 1

Align, calibrate, ICC profile; I don't care what handle you put on it. Get your proof to a midtone TVI value that mimics normal press conditions of 20% +/-2%.

Step 2

Make a set of non compensated plates using a test form that has a full 2% to 100% gradation for each color being tested. (KCMY) PIA/GATF, GRACoL, LithoTel, or custom)

Step 3

Check the press for proper packing, pH and conductivity and sequence of K,C,M,Y before running the test.

Bring the press to house densities. (Suggestion: K1.70, C 1.35, M 1.45, Y 1.05, +/-.05)

Balance the CMY screens to within +/- 2% of one another. TVI is not an issue at this point, but balance IS!

Bring the Black screens into full range print, (2/98) and keep the density to acceptable levels. Black will always come in fuller by virtue of the density and ink sequence.

Read your two color overprints for Red Green and Blue. (Prucel formula for KCMY rotation: Red= 65%, Green= 80%, and Blue= 70%)
Adjust ink / water balances on CMY to optimize the overprints as stated above.
Do not allow the midtone TVIs to vary by more than +/-2% from one another.
If you can not get the traps to optimize with the TVIs in balance then you have an ink formulation problem that needs to be dealts with by your supplier. (tack / viscosity / pigment to vehicle ratio / transparency etc.)

If you were successful in balancing the TVIs, and the two color overprints then you will be left with the "TRUE" gray balance densities (ink film thicknesses) and water settings the press man should be using to start a makeready with.

Step 4

Read a series of samples to get a good average set of numbers for density, TVI (dot gains), trapping, (Prucel formula and spectral L ab CMC) from the press.

Step 5

Take this information back to pre press and make the appropriate curve adjustments in CTP that will bring the press to the same TVI levels as the proofer. (Black may need a dedicated curve at CTP)

Compare the spectral values for solids and overprints from the press (at gray balance) and the proofer. Adjust the proofer's ICC profile to match the press at gray balance.

Conclusion:
All future color corrections should be made in PhotoShop, not on the press. PhotoShop is an infinitely adjustable digital environment.
The conventional offset press room is an analogue environment, constained by the very nature of the offset process itself and bound by the mix of consumeables it uses. The press is often maligned as "having a lot of variables" therefore it should adjust to the proof color. BS!

The press has a lot of variables and adjustments that can be made; the net effect of which can be measured and quantified. These metrics are easily harvested with todays press side scanners and closed loop systems. Once these systems are loaded with the proper specifications for achieving gray balance, these presses become extremely repeatable. What's more, they become valuable assets to the prepress operations for monitoring color changes due to mechanical or consumables failures.

There's an old addage about trying to put 10 pounds of "poop" into a 5 pound bag. It doesn't work. The proofs must always act as a precursor of what is to come when the job gets on press. This is how you make money printing in today's marketplace. Complying with pre press standards that are not based on what is achievable off press are foolish at best. Just my two cents.
Retroman

 

[DI Fan]

I have to agree with Herr Senefelder. I think the guy justs wants his proof and press to match. Does not sound like he cares about all the industry, ISO, GATF or FOLGRA standards (although, those are important). Proofers generally have a wider color space than offset. It's hard to get a press (with all its variables) into the same achievable color space as a good proof.

What i've always done is get the the press to a standard. G7, SWOP or whatever you want. Correct density, dot gain and a good clean print. New blankets, pates and blankets packed correctly, rollers set correctly, good house paper. 100lb gloss text will give desent stability. A good number one or two sheet. Keep a good record of how you got your final results on press. This will help you get back to that sweet spot when you stray from it, and trust me you will.

Now you have a nice, clean and correct standard. Save these plates and press sheets and store them correctly. Now print an IT8 target press sheets using calibrated plates just like you made for the first run. Using a spectrophotomer an ICC profile can be made. This will give you the color space that your press can achieve. Apply the profile to the proofer and you should be pretty close. May have to tweek it here and there.

If you have no clue how to do this or wheather your system can suppot it, there are lots of color management guys who can help.

 

[DI Fan]

Bingo.

Retroman's right.
make the press the best it can be first. These are coditions that can be repeated when needed.

 

[Greg Imhoff]

Fingerprinting 101

Fingerprinting 101

Dear Skinflint: To simplify Gordo is “spot on” due to naturally occurring press variables and the need to identify conditions where they exist. To arrive somewhere you first need to know where you are beginning.

To affordably identify how your press is printing, simply apply a Digital Wedge from UGRA or from your plate supplier. Drop the wedge into an open window for normalized workflow so after RIPping you see true output resolution and other visually helpful keys.

Drop the digital wedge into open areas on any normal jobs run to client acceptable or in house ink Densities.

Then fingerprint the press from say 10% to 100% to determine all aspects of each CMYK press curve on house inks, blankets, packing, plates etc.

Once your “normalized press curves” are known, then linearize your CTP plate outputs to be flat i.e.: a 10 = 10; 50 = 50, etc.

Then apply ICC profiles to your proofer for matching the smaller gamut of your press. This way you’re producing proofs that meet client expectations, you will make-ready faster and your press operators will not need a lobotomy.

For more detail contact me off line requesting the “Applied Densitometry Manual” from my Gretag days for a PDF in layman’s terms, graphs, specs, etc. how to and easy to read.

Sincerely,

Greg Imhoff
Director EPG Color Solutions
(860) 767-7130 office
(708) 557-2021 cell
Essex Products Group | Integrated Color Control Systems
[email protected]

 

[Michael Ditchett]

I'll disagree with that last statement.....Prepress proofing should be targeting a *standard* printing condition (ISO/Fogra or GRACoL/SWOP in the USA) by using the standard characterization data. The pressroom should be made to conform to this *standard* proof via plate compensation curves or perhaps device link profiles.

Bring the press to the (standard) proof, not the other way around! If you start by profiling the press and making THAT your proof "standard", you'll be chasing those presses with your proofing system from now to eternity! Never set your shop standard on the most variable piece of equipment in the plant.



Regards,
Terry Wyse

Totally agree with Terry. Bringing Prepress to Press is like asking the cowboy to enjoy a smooth ride on the bull.

 

[meddington]

. The proofs must always act as a precursor of what is to come when the job gets on press. This is how you make money printing in today's marketplace. Complying with pre press standards that are not based on what is achievable off press are foolish at best. Just my two cents.
Retroman

Agreed, however, today more than ever proofing systems are able to be just that...a pre cursor of what's to come on press. Actual press characterization data is available to tune proofing systems toward the devices they are to mimic. Further, I'd be vary careful when recommending proofing systems be tuned to a specific TVI value, then CTP used to adjust press output to the proofer's TVI. Densitometers use filtration tuned to process printing inks, and the different spectral properties inkjet inks compared to process printing inks can result in discrepancies. Further, adjusting ICC profiles of the proofer to match the press's gray balance...well, now the proofer is deviating from it's original "target", and this could lead to the necessaity for corrections needed upstream to the files prior to proofing, problems in accepting "standard" proofs from third parties, discrepancies between two presses at the same facility. Just my opinion, but I would optimize the press and the proofer independent to each other, but both toward the same target...ISO 12647-2 or G7.

 

[DI Fan]

OK.... tell how to do it.

Its easier to get the Iron to a happy place, then make the digital stuff match.
the idea here is not to spend weeks and valuable press time getting this done.

 

[danremaley]

press finger printing

press finger printing

I believe that the 'correct color' should be represented by the proof. The proof should be represent the separation. Most seps. are made in Photoshop by the customer. Most use SWOP or U.S. Prepress. All of the screen builds, logos and tints are based on the same standards. The press should print to the standards (whichever is selected). There are values for TVI (dot gain) and density, Lab, etc. per the standard selected. Felix Brunner of System Brunner fame, says that 80% of print problems are related to dots and 20% related to solids. What do most printers measure? Yep, density - 20% of the problem!
Walk in any pressroom in the U.S. most press sheets do not have a 50% patch tint or a 50% gray patch to measure. so how can you control what you can't measure?
There has always been targeted values, but few printers use them because the color bars are incorrect. Komori is one manufacturer that has 50% and 50% gray, probably because GATF made their color bars!
If we take the position that the proof is to match the press (largest variable) then every file would look different everywhere it was printed! I don't think the customer want's the color "different" depending on where it's printed. In fact a study from NAPL/GATF asked the number one reason for reprinting a job. It wasn't because of 'bad' color or even 'wrong' color it was "inconsistent" color! If the press sheet isn't at, or near, the 'standard' it may be in a difficult place to print throughout the run.
The standard numbers for SWOP, ISO, GRACoL, G-7 are all based on gray balance throughout the tone scale. Printing is simple, there are only two places you can print - in gray balance or CASTED and casted ruins all the color. So there is only ONE place you can print - in gray balance and if you print to the standards then you'll be in gray balance.

You can call me with any comments, questions. See attached files. . .
Dan Remaley (former GATF)
Process Control Consultant
412.889.7643

 

[Hanson]

It depends. This is an offset press, right? Running standard inks? What is so different about the paper? If it's only the color the best route might be to have someone edit the white point of a standard profile for that paper type to match that particular paper (e.g. coated/uncoated, bright white, etc.). This will be the reference profile for the proofer. If the paper is something really strange then a custom profile might be made, but try to avoid this at all costs--and the costs to do it right would indeed be very high.

Mike

yes, it's offset. let's say running by the ISO2846 ink. And the paper is paperboard and spectral value is different with ISO 12647-2. So my question is :

1/ should I follow the ISO 12647-2 to identify the LAB value of solid ink on paper. if can't what standard should I follow?
2/ base on situation as upper, can I just run the 50 gray to match the 50k on LAB value at first then write down the density of cmyk solid accordingly.At same time use these density values as my packaging printing standard?

 

[Hanson]

1. Linearize and profile your Colorproof to your chosen inkjet device (i.e. Epson), using the Color Manager.

2. In the proofing workflow of the EFI rip, set the "source" profile to GRACoL 2006. That profile can be obtained on the internet or newer versions of Photoshop, if your Colorproof doesn't already have it. Part of the challenge is terminology. EFI (and other software) call this the "source" profile, which is correct in some sense, but it is often more intuitive to think of it as the target or destination profile. This confusing terminology was half the

for the situation of proof solid density is different with the density of press how to deal with it. re-press the fingerprint to get the same density on press?

 

[William Campbell]

for the situation of proof solid density is different with the density of press how to deal with it. re-press the fingerprint to get the same density on press?

No. As I said in the earlier post, "Print where ink film thickness is comfortable. The press room can make that determination." That was my quick and dirty version of the post by Retroman, which is far greater detail about how to get a press printing "right." A great post in fact, very relevant to this subject. I particularly liked the "poop" adage, my version of which usually goes, "shine a turd."

However, there are volumes that can be said about the topic of how to make a press print right, which I wasn't planning to go into, rather concentrate on what we do at the prep end. The bottom line is to get the press room to make the it "their version of right" using linear scales, then you have something to measure that tells you how that press performs, when the people operating it feel everything is adjusted correctly. That's the press printing the best it can. Then we use plate curves to make prep (and proof) and press all agree. Don't force the press to print any particular way other than what the operator would consider "right." For a press, right is not any absolute numbers, other than ink film thickness, for those who actually use such a gauge these days. Does anyone?

About the difference in solid ink density -- yes, that's a problem with this scheme, but in most cases (provided the difference isn't drastic), factoring the numbers will work, as I explained (probably too quickly) in the last post. Even with seemingly crude methods, the results I've obtained across multiple printing companies has been favorable (I only do trade prep currently, so our plates run in multiple shops, varying environments from sloppy to tight).

What I mean by factoring is, for example: say the press prints cyan at 1.32. But you measure the proof and solid cyan is 1.27. Do the math... 1.27/1.32 gives a factor of 0.9621. Make a spreadsheet, record 5, 10-90, 95 and 100 from the press sheet, and make another column that applies the factor to those numbers. Use those factored numbers to find your value on the 100 step scales.

When I do this I actually use a Fuji FinalProof for my 100 step scales from which I search out the value. So that helps get more accurate results, since the Fuji colorants are far closer to real ink than any inkjet. But it can still work with an inkjet. Just don't expect as exact a result on the first try, it might take a couple adjustments, but still, the result is far closer to right than guessing at some standard test images. That subjective method of calibrating a press is horrible, and unfortunately, is used often. Do it by the numbers, the best numbers you can come up with.

In many cases the first try hits nearly perfect. In a few cases, and those where we really want to fine tune, the process can be repeated with a "curve-applied" scale running through a gutter of a live job. We measure that and see how far we are from a straight (linear) result. Say next time around 50% is now reading 48% (determined by comparing densities). We're closer, but need to move another 2%. Repeating this process, you can arrive at a perfect plate curve. Eventually, it's like flying a plane and not able to get the wings level... the result is 2% high, then 2% low, back and forth. That means you're done--as close as you're going to get.

I have a spreadsheet of pre-measured 100 step scales from a FinalProof tuned to G7, which I use to accomplish this trick. My local competition need not inquire, but others I'd be willing share if you want to contact me off-line: [email protected].

William Campbell
Revere Graphics - Portland, Oregon
Sci-fi adventure on-line: Dead Forever by William Campbell

 

[Retroman]

Press Fingerprinting

Press Fingerprinting

I believe that the 'correct color' should be represented by the proof. The proof should be represent the separation. Most seps. are made in Photoshop by the customer. Most use SWOP or U.S. Prepress. All of the screen builds, logos and tints are based on the same standards. The press should print to the standards (whichever is selected). There are values for TVI (dot gain) and density, Lab, etc. per the standard selected. Felix Brunner of System Brunner fame, says that 80% of print problems are related to dots and 20% related to solids. What do most printers measure? Yep, density - 20% of the problem!
Walk in any pressroom in the U.S. most press sheets do not have a 50% patch tint or a 50% gray patch to measure. so how can you control what you can't measure?
There has always been targeted values, but few printers use them because the color bars are incorrect. Komori is one manufacturer that has 50% and 50% gray, probably because GATF made their color bars!
If we take the position that the proof is to match the press (largest variable) then every file would look different everywhere it was printed! I don't think the customer want's the color "different" depending on where it's printed. In fact a study from NAPL/GATF asked the number one reason for reprinting a job. It wasn't because of 'bad' color or even 'wrong' color it was "inconsistent" color! If the press sheet isn't at, or near, the 'standard' it may be in a difficult place to print throughout the run.
The standard numbers for SWOP, ISO, GRACoL, G-7 are all based on gray balance throughout the tone scale. Printing is simple, there are only two places you can print - in gray balance or CASTED and casted ruins all the color. So there is only ONE place you can print - in gray balance and if you print to the standards then you'll be in gray balance.

You can call me with any comments, questions. See attached files. . .
Dan Remaley (former GATF)
Process Control Consultant
412.889.7643

Hello Mr. Remaley and Mr. Meddington

Retroman here.
Thanks for jumping in with your helpful insites into the process of fingerprinting the press.

I totally agree with your quote: "I believe that the 'correct color' should be represented by the proof. The proof should be represent the separation."

If the proof is doctored to mimic a color gamut that is not "true to the separations as they will be printed by the printer's press inks"; then you are already starting the job on a slippery slope.

I also concur with this statement;
"There are values for TVI (dot gain) and density, Lab, etc. per the standard selected."

My only comment here is that these values also need to be applied at prepress to the contract proofer if it is to reflect what is to be printed on press.

Lastly, your comments on Mr. Brunner; my hero. He had it right, way back in the 80's. Problem was nobody really understood or listened to the message back then. We were all too busy making money with the fat margins that print still had going for it.

"Felix Brunner of System Brunner fame, says that 80% of print problems are related to dots and 20% related to solids. What do most printers measure? Yep, density - 20% of the problem!

The only comment I have here is that screen (TVI) balance is mainly important up to 65% builds, at least in my experience. After 65%; overprint trapping is the major player in determing color, with density mainly responsible for controlling contrast levels.

Mr. Meddington, I agree with what you say, however I do have something to add to your statement;
"I'd be vary careful when recommending proofing systems be tuned to a specific TVI value, then CTP used to adjust press output to the proofer's TVI."

Anyone out there running a press will tell you that once the proper ink / water balances are set at press there is little to no control over TVI. The press only follows the message on the plates. Sure you can get higher tack inks, quick release blankets, and costlier fountain solutions, but at the end of the day this isn't reality for most printers due to the added costs. The only manageable way to set FINAL TVI values at press is through CTP adjustments. It's digital. It's repeatable. It can be measured and controlled independent of press.

"Densitometers use filtration tuned to process printing inks, and the different spectral properties inkjet inks compared to process printing inks can result in discrepancies. Further, adjusting ICC profiles of the proofer to match the press's gray balance...well, now the proofer is deviating from it's original "target"

I agree with what you are saying about densitometers and their filtration, that's why we should be advocating the use of spectrophotometers for color measurement. No filters. Look at updating to the X-Rite and Techkon hand held spectros for all color measurement.

The "original target" IS the press at the end of the day. Make a proof that looks like how the press will reproduce the digital files.

For sure this leaves the industry with some "flawed specifications" but this is reality. Not all presses print or can be made to print to the same exacting standards that are being foisted onto this industry, however most can print to gray balance. The simple answer is that the presses are uniquely different in manufacture and age, and the consumables manufacturers do not, contrary to popular belief supply products that give identical color rendering performance one to the other. Papers are different from mill to mill. Ink formulations vary supplier to supplier and from batch to batch. Press operators vary in skill sets and work habits from shop to shop. Plate graining, which in turn influences color varies from one manufacturer to another.

The only real hope for today's challenged printer is to be able to show a proof to his client that he can faithfully reproduce through his printing process. Anything less than this is really no help at all. We as an industry need to take a hard look at these "standards" and try to decide if they really are helping our North American printers or if they are making them less competitive on a global scale.

Most printers that I know, and I know quite a few, are mainly concerned with getting the job accepted and paid for. If that means matching their in house proof and not an industry standardized proof, then that's what really happens.

Don't get me wrong, I'm not against standards, Quite the contrary, attainable and meaningful standards would be good for printing, but all suppliers have to come to this party and be made more accountable for what they supply into the chain. This means rethinking G7, SWOP and the like. Gray balance is the right way to go, but all who influence it need to adhere to a common set of standards. The printer can't perform this feat alone.

 

[meddington]

Mr. Meddington, I agree with what you say, however I do have something to add to your statement;
"I'd be vary careful when recommending proofing systems be tuned to a specific TVI value, then CTP used to adjust press output to the proofer's TVI."

Anyone out there running a press will tell you that once the proper ink / water balances are set at press there is little to no control over TVI. The press only follows the message on the plates. Sure you can get higher tack inks, quick release blankets, and costlier fountain solutions, but at the end of the day this isn't reality for most printers due to the added costs. The only manageable way to set FINAL TVI values at press is through CTP adjustments. It's digital. It's repeatable. It can be measured and controlled independent of press.

I wasn't suggesting that TVI should be/could be effectively adjusted on press, only that the target for press TVI should not come from the proof, particularly an inkjet proof. Rather I'm suggesting it should come from standard data (if TVI is to be used at all).

I agree with what you are saying about densitometers and their filtration, that's why we should be advocating the use of spectrophotometers for color measurement. No filters. Look at updating to the X-Rite and Techkon hand held spectros for all color measurement.

If we're still refering to TVI measurement, even with a spectrophotometer, the weighting factors for determining TVI from spectral data are also based on process printing inks, and the same situation can apply.

I guess my main point is that you need more than TVI values to adjust your proof, and the the target data from your press should come from something other than a proofing system. This was less problematic with laminate systems than with inkjet, but laminate systems can have there own short comings.

For sure this leaves the industry with some "flawed specifications" but this is reality. Not all presses print or can be made to print to the same exacting standards that are being foisted onto this industry.

This is true, though I have seen some impresive examples from multiple printers using different makes/models of equipment targeting industry "standards" that all visually matched a "standard" proof. Not something that one would traditionally expect from this industry.

Overall though, I think we can agree that consistency is going to be more important than the chosen target. If you're hitting house specs and pleasing your clients, no argument from me.

 

[Alois Senefelder]

re Press Fingerprinting !

re Press Fingerprinting !

Hello Gentlemen and fellow Lithographers,

It would seem I've caused a Interesting Controversy !!! - so onto Mr. Retroman's Hero

Felix Brunner - "Offset Quality Control with the Brunner System" PDFs


Regards, Alois

"From knowledge to competence is a great step --- from ignorance to competence an even greater one"

 

[Alois Senefelder]

Brunner Part # 2

Brunner Part # 2

Continued -- Brunner System

 

[Alois Senefelder]

Brunner Part # 3

Brunner Part # 3

Continued - Brunner System, the last so "I hope you will find it of Interest and Value"


Regards, Alois

PS I also posted a PDF on the "Halftone Dot " in Thread: Print Contrast - Date 05/22/2009

 

[Retroman]

Hello Alois

Thanks for the PDFs. They may be somewhat dated with their reference to film, but they are like the "Dead Sea Scrolls" of Litho. They are still very valid today. I encourage everyone to look through them. There is still a lot of room in today's digital environment for conventional wisdom.

Retroman

 

[danremaley]

Hello Mr. Remaley and Mr. Meddington

Retroman here.
Thanks for jumping in with your helpful insites into the process of fingerprinting the press.

If the proof is doctored to mimic a color gamut that is not "true to the separations as they will be printed by the printer's press inks"; then you are already starting the job on a slippery slope.
>>>The proof, using an icc profile, is correct colormetricly, based on the Lab patches, not necessarily density and dot area (of the press). However a correct proof will match a press sheet printed to the correct PRESS, Density, Dot Area and Gray balance.

The only comment I have here is that screen (TVI) balance is mainly important up to 65% builds, at least in my experience. After 65%; overprint trapping is the major player in determing color, with density mainly responsible for controlling contrast levels.
>>>>>The screen TVI is critical in the 40-50-60% range because when you add ink or remove ink this is where the gain and gray balance changes. Place a 50% gray and a 70% gray on the color bar and see which one "moves" and how much.
System Brunner opens and closed ink keys based on GRAY BALANCE not SID. It is the combination of these metrics that control color but as he states screens are more important than solids. Please see attached pdf. file it is the most important information that you'll ever need. Brunner and Heid. had a big fight over it's information.

Dan
412.889.7643

 

[gordo]

wrote:
>>>>>The screen TVI is critical in the 40-50-60% range because when you add ink or remove ink this is where the gain and gray balance changes. Place a 50% gray and a 70% gray on the color bar and see which one "moves" and how much.

I know this is heresy, however, the 3/C gray patches in a color bar do not share the same screen tint builds as the same tone values in the live 4/C image area and therefore cannot reflect the color shift caused by a change in solid ink density. As a result, the 3/C gray patch in the color bar is fairly meaningless for that purpose.

On a side bar, Brunner's gray balance is NOT based on color.
He does not use colorimetry (page 5 from your PDF: "Colorimetry is absolutely unsuitable for controlling the printing process and detecting process faults in illustration printing."). Instead, he uses densitometry and assumes a connection to color. A connection that does not always occur.

best, gordon p