Color Management: Dot Gain Curves, ICC Profiles, and a Hamster Wheel

[Red_Right_Arm]

We use Xante Symphony Flexo RIP 7.0. It has the ability to use ICC profiles, dot gain curves, and hybrid screening. It's basically the only thing we are using for color management. The people who were in charge before I was hired did not do a great job of creating a viable color management system. We currently only use three press profiles for seven presses. These profiles were created from one test back in 2011. On one substrate and one anilox. The ICC profile that is fed to the proofer is from one press, tested one time, on one substrate, with one anilox. So basically our proofer is making proofs that are being color corrected for only one printing scenario. That one ICC profile is creating the proofs that are used by all seven presses, regardless of what press settings/parameters they are actually using to run the job. I know. I know. There is work to be done.

So, it seems like there are dot gain adjustment curves and there are ICC profiles.

When we preflight a digital file, it goes from Illustrator, to the RIP, then to the proofer. The RIP handles all of what we can vaguely call color management. The RIP uses the one ICC profile to determine overprints, color densities, color adjustments, whatever you'd want from an ICC profile.

When the proof is approved, we send the same digital file we used for the proof. Only this time it goes to the RIP and gets deposited into one of three printing queues. These queues are basically presets that determine which dot gain curves to apply, which bearer bars, which control targets and registration marks. From there we set up our stepping and repeating and distortion from the RIP. The RIP generates the separated 1-bit TIFF files. Then those TIFF files go to the laser to image the plates.

So we have this RIP handling all of our color management. That's it. All of it. Everything passes through this one RIP. And this RIP is not best suited for the the different combinations of press settings/parameters that we'd need to control every possible press configuration. We're talking, like, 400+ possible combinations to have to keep under control. 400+ print queues, each with its own set of dot gain curves and such. 400+ ICC profiles to give to the proofer to predict what is supposed to happen on press.

Okay, anyway, so I'm trying to get all this under control. But I keep getting caught on the optimization, fingerprint, characterization steps for color management.

If we use the RIP to make a set of linear plates. Those plates will be used for the optimization trials.

Then we use the data we gathered from the optimization trials to make a set of fingerprint plates. But we will have made them before we've created any color management. No dot gain curves are made yet. No ICC profiles. These fingerprint samples are to be used as the standard for how the press should run. But we will not have them in color control yet at this point.

Then we make characterization plates. These plates have the IT8.7/4 characterization target. The IT8.7/4 characterization target is measured. ICC profiles are created. Dot gain curves are created. Now we have color management... sort of.

See, if you are supposed to use the fingerprint samples as THE standard for how the press should operate, but the fingerprint samples were created before color management, then once we start using color management won't it throw off all of the controls? Gray balance will be effected by the color management. Color adjustments will be effected by color management. Dot gains. Tint percentages. Ink densities. They'll all be effected by the color management. So how can the fingerprint be used as the standard, when we begin using color management AFTER the standard is created?

I've been told that whenever something changes we need to redo the optimization, fingerprint, and characterization tests. Which will produce another set of dot gain curves and another set of ICC profiles (all of which get stored into the RIP and used for proofs or 1-bit TIFFS for plates). These new color management files will be different again. Which will mean another round of optimization, fingerprint, and characterization tests. Which will produce another set of dot gain curves and another set of ICC profiles. Now something has changed again. So it requires another round of optimization, fingerprint, and characterization tests. Which will produce another set of dot gain curves and another set of ICC profiles. It's like a hamster on a wheel that never stops.

So, when does it stop? When are we done doing these tests? We can't endlessly keep doing round after round of optimization, fingerprint, and characterization tests.

 

[Correct Color]

Regardless of the machine or the situation, it works like this:

First you create a machine state, and then you characterize the machine in that state.

The machine state is everything that is variable and controlable in the process of reproducing colors with primaries: White point; ink chroma values; ink densities; tone curves; etc.

The characterization is the ICC profile. You apply the ICC profile to create dots to achieve the L*a*b* values of the pixels you're converting into that machine state.

The ICC does not alter any of the machine-state conditions, it uses them to achieve a color-managed result.

Y'know, I'd also point out that there's no shame in hiring a professional to come sort this all out for you. Trial and error and casting about for answers on the Internet isn't a really effective way to achieve the best possible results.



Mike Adams
Correct Color

 

[gordo]

Okay, anyway, so I'm trying to get all this under control. But I keep getting caught on the optimization, fingerprint, characterization steps for color management.

If we use the RIP to make a set of linear plates. Those plates will be used for the optimization trials.

Then we use the data we gathered from the optimization trials to make a set of fingerprint plates. But we will have made them before we've created any color management. No dot gain curves are made yet. No ICC profiles. These fingerprint samples are to be used as the standard for how the press should run. But we will not have them in color control yet at this point.

If you make your plates linear then you've effectively made dot gain curves.
The presswork from linear plates does not represent the standard for how the press should run.[/QUOTE]

You should take Correct Color's advice since your reference framework for understanding the process appears to be faulty and hence the conclusions you come up and the path you think you should follow become suspect.

 

[Red_Right_Arm]

Y'know, I'd also point out that there's no shame in hiring a professional to come sort this all out for you. Trial and error and casting about for answers on the Internet isn't a really effective way to achieve the best possible results.Correct Color

I agree. And if it were my company that's what I'd be likely to do. However, I've brought in four very reputable companies to evaluate our process and give us an estimate on what they'd suggest we do, how long it would take, and what they'd charge. Upper management hasn't approved the expense though. They believe that we already have the tools we need, the workflow is fine, and prepress operators are just supposed to intuitively know by gut feeling and experience what adjustments are needed to be made for every combination of machine state. So the next best thing I can do is try to learn on my own with the help of you fine people.

 

[Red_Right_Arm]

You should take Correct Color's advice since your reference framework for understanding the process appears to be faulty and hence the conclusions you come up and the path you think you should follow become suspect.

I'd like to. But I can't get the big wigs to approve the cost. If we did hire them, upper management will expect the current process to remain as-is, but have the colors corrected through this service. And when they don't alter the procedure to maintain the color management, the money will quickly go to waste when nothing is done to maintain the color management.

These people know how to print assuming that the pressmen are supposed to be able to monkey around on press, doing anything they want to get the job printed correctly, and whatever they do doesn't need to be verified. So instead of creating a standard set up for the press, and allowing color management to control the colors, they want to be able to mess with the anilox, color, color densities, as needed until the job starts printing the way that the uncontrolled proof looks.

We don't use impression targets or trap targets. Most of the time we don't use color blocks, and when we do we only use 100% and 50% color blocks. And even if we do load up on control targets in the bearer bars, it is common practice to chop the bearer bars off anyway. Color densities, ink viscosities, and ink pH aren't verified as the press is running unless QC finds a problem on their own. And these practices are defended by the general manager, COO, and owner. And these are the ones with all the practical experience who are trying to teach me how a flexo printing company ought to run.

So yeah. Total agreement. But until the big wigs change their minds, I'm on my own trying to untangle this ball.

 

[gordo]

I'd like to. But I can't get the big wigs to approve the cost.

The only way to get approval is to define the specific issues production is having and the associated costs to the business because of those issues. I.e. the economics of the situation. I.e. MONEY.

[snip]I've brought in four very reputable companies to evaluate our process and give us an estimate on what they'd suggest we do, how long it would take, and what they'd charge. Upper management hasn't approved the expense though. They believe that we already have the tools we need, the workflow is fine, and prepress operators are just supposed to intuitively know by gut feeling and experience what adjustments are needed to be made for every combination of machine state.[snip]

If they believe you already have the needed tools then if the situation is bad enough and doesn't improve then it's your head on the block. Seems like you need to update your résumé. If you want to keep your job then perhaps you should hire one of those consultants yourself for an 8 hour crash course on color management and process control. You should also do a deep dive into any book on the topic.

So the next best thing I can do is try to learn on my own with the help of you fine people.

You'll get some tweaks type help here but no one's got the time to give you a course on color management gratis.

These people know how to print assuming that the pressmen are supposed to be able to monkey around on press, doing anything they want to get the job printed correctly, and whatever they do doesn't need to be verified. So instead of creating a standard set up for the press, and allowing color management to control the colors, they want to be able to mess with the anilox, color, color densities, as needed until the job starts printing the way that the uncontrolled proof looks.

There's no problem working that way if the economics are acceptable to management.

We don't use impression targets or trap targets. Most of the time we don't use color blocks, and when we do we only use 100% and 50% color blocks. And even if we do load up on control targets in the bearer bars, it is common practice to chop the bearer bars off anyway. Color densities, ink viscosities, and ink pH aren't verified as the press is running unless QC finds a problem on their own. And these practices are defended by the general manager, COO, and owner. And these are the ones with all the practical experience who are trying to teach me how a flexo printing company ought to run.

Again, there's no problem working that way if the economics are acceptable to management.

But until the big wigs change their minds, I'm on my own trying to untangle this ball.

IMHO, just think about the money. If things don't change and the result is that your job is in jeopardy then you may have to foot the bill to get yourself educated - or start looking for a job elsewhere. If you think things could be better and are frustrated that management doesn't get it, then make sure that you document production yourself so that if the $#it starts to fly you have documented back up as to why you were not responsible. Meanwhile start putting discreet feelers out for a job elsewhere.