Color Management

Prepper

Well-known member
Question #1, is it possible to make color management work strictly from within prepress? If the pressman isn't on board and doing their part such as monitoring dot gains and trying to keep them within a certain tolerance, for example, +\-4%, will color management using G7, profiles, curves, work at all or very well? If dot gains aren't monitored, only densities, would it be better to just forget curves and go linear? My thoughts have led me to think that wrong, bad, or outdated curves may be worse than linear or no curves at all?

Question #2: During production runs, all I read suggests something on the order of +\-10 density points as a tolerance. Is this what most go by, something higher or lower, or nothing at all? Do you have an established tolerance and if it drifts out of that do you save the sheets? All honest :) answers appreciated. Just trying to determine if we are being too strict with our expectations. Recently experienced 10 press runs first hand by helping out there and on these short runs of 2800 plus 1000 sheets startup each run, I'd say only 10% would have probably met a +\-10 tolerance, saw some that were +40 to -20 in black, on the same sheet even, what I saw was that it took that many sheets for it to get leveled out and approaching being within that tolerance. This is the same thing I've experienced when pulling targets for curves, it would take two to three thousand sheets for them to get one or two P2P targets into a +\-5 density range. We do not have presets or closed loop color, is this what we should expect on a 19x25 short run 4-color job on a mid-1990's Heidelberg? I realize we are only trying to minimize the amount of variation at best and trying to determine if we have unrealistic expectations? We are an in-plant, so printing for ourselves, what would be your maximum tolerances for density variation before you'd be afraid of your customer noticing and you having to reprint or give credits? I realize it depends on the colors you're laying down to a certain extent so do you go by how close it's matching the proof, like some colors can vary a lot and still look pretty good compared to the proof but sometimes certain colors can be within tolerance and look different than the proof still. Do you follow a hard and fast rule of tolerance or is it left up to the pressman's judgement?
 
Question #1, is it possible to make color management work strictly from within prepress?

No. To be successful, color management involves management, prepress and pressroom involvement.


If the pressman isn't on board and doing their part such as monitoring dot gains and trying to keep them within a certain tolerance, for example, +\-4%, will color management using G7, profiles, curves, work at all or very well?

Monitoring dot gains is not the press operator's job. The press operator is responsible more for laying down a film of ink in a reliable consistent manner. If a spectro is available then checking the Lab values of the process inks can be a QC activity that can be done by the press operator. It is the responsibility of prepress to provide the pressroom with plates that result in presswork aligning with the proof once the target SIDs are achieved.

[/QUOTE]If dot gains aren't monitored, only densities, would it be better to just forget curves and go linear? My thoughts have led me to think that wrong, bad, or outdated curves may be worse than linear or no curves at all?[/QUOTE]

No, dot gains occur whether you run linear or not. Prepress needs to make sure that the appropriate curves are applied during plate imaging.

Question #2: During production runs, all I read suggests something on the order of +\-10 density points as a tolerance. Is this what most go by, something higher or lower, or nothing at all?

+\-10 is the traditional tolerance.

Do you have an established tolerance and if it drifts out of that do you save the sheets?

In my experience, most commercial shops have an established +\- range for SIDs. Publication printers tend to stick with the standard +/- 10 points. A well run shop tends to monitor things like SIDs to make sure that if there is deviation from the standard that there is a known reason for that deviation.

Recently experienced 10 press runs first hand by helping out there and on these short runs of 2800 plus 1000 sheets startup each run, I'd say only 10% would have probably met a +\-10 tolerance, saw some that were +40 to -20 in black, on the same sheet even, what I saw was that it took that many sheets for it to get leveled out and approaching being within that tolerance.

A printing press needs to run a certain amount of sheets before things settle down to stability. With short runs there may not be enough time for that point of stability to be reached.

This is the same thing I've experienced when pulling targets for curves, it would take two to three thousand sheets for them to get one or two P2P targets into a +\-5 density range.

Yup. That is press and environment dependent. A press run is stable - but not consistent.

We do not have presets or closed loop color, is this what we should expect on a 19x25 short run 4-color job on a mid-1990's Heidelberg?

In most cases, ink key presets (vs eyeballing the plate) will dramatically reduce makeready times. Closed loop color control will also help the press operator get to the correct density points.

I realize we are only trying to minimize the amount of variation at best and trying to determine if we have unrealistic expectations? We are an in-plant, so printing for ourselves, what would be your maximum tolerances for density variation before you'd be afraid of your customer noticing and you having to reprint or give credits?

Aim for +/- 10 points but realize that your short runs may not make this possible. How far away from aligning presswork to proof you are before the client will reject the job is job and client dependent.

I realize it depends on the colors you're laying down to a certain extent so do you go by how close it's matching the proof, like some colors can vary a lot and still look pretty good compared to the proof but sometimes certain colors can be within tolerance and look different than the proof still. Do you follow a hard and fast rule of tolerance or is it left up to the pressman's judgement?

Any off press proof involves a potential compromise in color alignment between presswork and proof. Prepress and pressroom need to work together with the support of management to make alignment a good as it can be. E,g. the proof setup to an industry standard, the plates curved to allow tonal alignment at the appropriate densities, and the ink hue sets on press aligned to the appropriate industry standard. Then eliminate as many of the variables as possible that would cause deviation from the shop targets.

best, gordo
 
How does prepress adjust for continually changing conditions at press that affect dot gains without ever knowing about those changes ahead of time?
 
How does prepress adjust for continually changing conditions at press that affect dot gains without ever knowing about those changes ahead of time?


You draw a line straight through it.

Most shops use several plate curves...e.g.
one set for gloss coated,
one set for matte coated,
one set for uncoated.

The press runs to specific SIDs for each of these substrate types with plates that have been curved for each substrate type.

If set ups have been done correctly then that'll get presswork very close to proof alignment with a few minor tweaks.

gordo
 
"If setups have been done correctly...."

"If setups have been done correctly...."

You draw a line straight through it.

Most shops use several plate curves...e.g.
one set for gloss coated,
one set for matte coated,
one set for uncoated.

The press runs to specific SIDs for each of these substrate types with plates that have been curved for each substrate type.

If set ups have been done correctly then that'll get presswork very close to proof alignment with a few minor tweaks.

gordo

"If setups have been done correctly..." is the hanger here for me I guess. If you mean press setups, then you are assuming the pressman is on board and doing his part, which if setups are done correctly will take care of keeping dot gains somewhat consistent. Preface all this by saying we are a one shift, one press in-plant running on one gloss coated stock most of the time. But if the pressman changes the inks from medium tack to light tack in 2 of the 4 units, tries a different blanket in half the units, tries different rollers in half the units, and runs the job on 4 different papers, all on the very next jobs after curves runs were done and new curves made and applied AND never said a word to anyone about it, AND never noticed that the 2 different ink tacks weren't trapping so the color was pretty far off during that job. I noticed it before they finished it, told them about it, started troubleshooting to figure out what was going on and found out all the previous info from our other pressman. They had to stop, clean out the ink and start back up and color was okay again because trapping was working. This to me is what you'd do as a worst case scenario to see what will happen, how could a pressman with 20+ years on a press ever think that this would work? He also thinks we shouldn't have proofs either so he can just run it without having to compare it to anything because when it doesn't match too well he says, "we should just throw the proof out and not let them see it, I think the press sheet looks better anyway."

This is what I mean by it won't work if the pressman isn't on board and doing his part. This is what I mean when I tell them that no amount of curves, profiles, GCR, etc can adjust to keep those kinds of changes in line with a proof, right? That was a severe case, to say the least, but that's how far off we are from being able to get him on board and abide by any sense of consistency, he has to think it doesn't matter, but then again, he can also see that the color was off and didn't work, but he still thinks it's ok because he was getting rid of some extra ink he had sitting around from samples he had tried before, you know, saving us a few pennies. Sorry, original post probably mis-leading in that you were thinking we're dealing with a normal situation where people work together, try to get on the same page and produce the best job they can and take pride in being able to do that.

Thanks, sorry for the rant, just very frustrating going thru this time and time again, for years.
Tremendous workplace, very difficult personnel situation.
 
Pre-press cant fix a pressman that cannot print properly just as a top notch pressman cannot fix bad prepress. Your pressman may not be the right guy for your company. Maybe time for a change if he cannot grasp the way business is run today. There are a lot of good press people out there who want to and can do a good job.
 
Pre-press cant fix a pressman that cannot print properly just as a top notch pressman cannot fix bad prepress. Your pressman may not be the right guy for your company. Maybe time for a change if he cannot grasp the way business is run today. There are a lot of good press people out there who want to and can do a good job.

That might be very true.
Two other possibilities.
Perhaps he's having issues on press and is trying to solve them without engaging other people. There can be many reasons he wouldn't engage other people - including fear. It may be just a simple manner of education as to what is done in prepress and how it impacts the pressroom as well as how what he does on press affects the integrity of the manufacturing process.
It's also possible that he does not understand the connection between his activities, the shop's ability to remain finantially viable, and his continued employment and salary. I have giving many seminars to help press operators understand the economic impact of their part of the manufacturing process.

If you can't get through to him then you have two coices.
Either ignore the issue but document all the issues to cover your butt.
Or bring the issue up with management backed up with documentation as to the negative economic impact on how the shop is run. Also provide an action plan to resolve the problems. Then it is up to them to make the needed changes.

Gordo
 
I'll just echo what Gordo said. You can only do so much. If the rest of the chain isn't on board, and you've exhausted all your options, then so be it. You did what you could.

Just document everything.
 

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