Colorbars, print contrast, tints, relating to G7

BeauchampT

Well-known member
I think I'll toss in at this point....

I agree wholeheartedly that ultimately once the press is set up properly, all you should need to do is run to SD. That being said, I have found that when the operators have a full knowledge of the entire process, they are interested in knowing what the dot gains are as it becomes a troubleshooting tool for them.

In our plant, we ahve tried to promote a culture where everyone views colour management as a tool that helps with multiple steps, not just getting the print and proof to match. For our operators, especially newer ones, we are teaching them to view a problem with print-to-proof match as their opportunity to identify mechanical and chemical issues in the process.

I've noticed that the ones that start to grasp this become really good operators. They are on top of blanket changes, form checks, chemistry changes, etc. Those that don't get it tend to complain that 'the artwork must be off' or that 'i can't do anything about it'.

Anyways, I love the fact that our colour bars include solid density, highlight and shadow tone dot gain patches, grey balance patches, overprints, and slur patches. They have helped me solve a lot of mechanical issues over the years (slur patches for example have helped with multiple tension setting issues, not to mention narrowing down a problem in our rollstand to a faulty encoder that needed to be replaced). But i suppose that at times a little knowledge in the wrong hands is a dangerous thing....depending on the plant.
 
D

Deleted member 16349

Guest
A lot of the recent posts have been interesting for sure.

As I see it.

Prepress, even though it is digital, still does not result in predictable colour basically because the methods do not clearly lead to that result. Mathematically they do not predict colour.

The press does not print consistently since it can print the same screen differently around the plate cylinder that is in line with the SID control patch. The differences in how it prints is related to the image it is printing. It is not independent of the image. Therefore printing a test form, does not result in data that represents how the press will print for any other image except that form.

As Gordon has correctly stated. The press prints ink films. That is the basis of what it does. It does not print colour but colour is the byproduct of the printing process. The purpose of the design of the press should be to manage how the films are printed and to make them consistent and predictable.

So the sad part of this is that these goals above are not met and the printing community does not have a strong interest to get things right. They rather let all of you suffer frustration in your attempts to make things work with inadequate technologies. They do this because they have not idea what to do. They base their efforts on the hope that somethings will work and not on a clear understanding of what should be done to get things to work.

OK, the whole problem is not so easy to correct because there are many relatively simple problems happening at the same time. Looking at just a small area of the process does not help because one needs to be able to see the whole picture. Most people can not do this and the industry can not do this. And they won't take any advice either.

It is kind of funny to think that in an industry that is about producing images, you have the blind leading the blind.
 
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Prepper

Well-known member
You think he should know the TVI targets?

@gordo

No, but as a way of knowing if things do change, where to look. And not targets necessarily but what his normal everyday TVI is maybe? So if things are too red, he looks at magenta TVI, it's normally around 18 and now its 24, then hey, there's why it's too red, or more red than it used to be. Now is there something he can do about it? I don't know but he would know where to start looking. That seems to be someone else's job though. Adjust the curves and fix it for me. There is something to be said for that if you're changing papers back and forth and in saying that there's 100 variables most of which he has no control over and doesn't understand, unless he's someone that studies and researches it.
 

gordo

Well-known member
You think he should know the TVI targets?

@gordo

No, but as a way of knowing if things do change, where to look. And not targets necessarily but what his normal everyday TVI is maybe? So if things are too red, he looks at magenta TVI, it's normally around 18 and now its 24, then hey, there's why it's too red, or more red than it used to be. Now is there something he can do about it? I don't know but he would know where to start looking. [snip]

Here is a big difference between the pressroom and prepress (and it's not that it's called "the pressroom" but it's not called "the prepress").

Jobs that come into prepress are all over the place in terms of their content, setup, etc. There's a tremendous inconsistency in the nature of inputs.

But it's a very different situation in the pressroom.

Every job is basically the same. The inputs, plates and proofs tend to be very consistent. As are the tools being used - blankets, press, inks, fountain solution etc. Effectively press operators are doing the same job over and over every hour and every day. When you do the same thing over and over you get to know it very well indeed. You know, for example, what a halftone dot should look like and know what is wrong if it doesn't look the way it should. You know when the film of ink is transferring correctly and when it is not. You also know how long your makeready should be and how far you can go with massaging the parameters that you control in order to align with the proof. Whether the magenta has a TVI of 18 or 24 really doesn't matter.
 

alibryan

Well-known member
Here is a big difference between the pressroom and prepress (and it's not that it's called "the pressroom" but it's not called "the prepress").

Jobs that come into prepress are all over the place in terms of their content, setup, etc. There's a tremendous inconsistency in the nature of inputs.

But it's a very different situation in the pressroom.

Every job is basically the same. The inputs, plates and proofs tend to be very consistent. As are the tools being used - blankets, press, inks, fountain solution etc. Effectively press operators are doing the same job over and over every hour and every day. When you do the same thing over and over you get to know it very well indeed. You know, for example, what a halftone dot should look like and know what is wrong if it doesn't look the way it should. You know when the film of ink is transferring correctly and when it is not. You also know how long your makeready should be and how far you can go with massaging the parameters that you control in order to align with the proof. Whether the magenta has a TVI of 18 or 24 really doesn't matter.


While the incoming files for prepress can vary greatly in the way they are setup, once they are manipulated by prepress and ripped for plating, they are all going to come out the same. Meaning once the plates get to the pressroom, they are (for the most part) going to be the same in what's required of the press operator to produce the job. Like you said, it's the same thing in terms of loading the stock, hanging plates and setting up for the run.

The ink densities required for every job (if the prepress is done correctly) are going to be the same as well. So all of the other things should be the same in terms of TVI, grey balance, trap, gain, etc.

When they aren't, it's usually going to be because something on the press has changed. I don't know what but like I said, all the elements in the color bar should read the same, job after job. And since prepress is putting out digitally produced plates there are no variables there. Especially in the color bars...
 

alibryan

Well-known member
So if things are too red, he looks at magenta TVI, it's normally around 18 and now its 24, then hey, there's why it's too red, or more red than it used to be. Now is there something he can do about it? I don't know but he would know where to start looking. That seems to be someone else's job though. Adjust the curves and fix it for me. There is something to be said for that if you're changing papers back and forth and in saying that there's 100 variables most of which he has no control over and doesn't understand, unless he's someone that studies and researches it.

@Prepper

I don't know your experience level but it appears that you know prepress well enough to say that you are doing your job correctly. Your press operator is coming up with different values on press but it doesn't sound like that's because of what you're doing.

You haven't said what type of equipment you have in prepress or the pressroom and it doesn't really matter. Mainly because no matter what you say, no one here is going to be able to solve your problem completely. Without being there to see what's happening on press firsthand, (plates, paper, ink, pressures, condition of press etc.) all anyone can do is guess where the problem lies.

IMO, the problem is coming from the press side of the equation but even if that's true, how does that help you? Can you go to your operator and tell him that it's his fault and he needs to fix it, because someone on the internet (who has no idea who he is or what he's doing on press) told you so?

It seems to be an interesting dilemma and I wish you the best of luck in solving it. Maybe someone here has a different idea on what can be done.
 
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BeauchampT

Well-known member
Every job is basically the same. The inputs, plates and proofs tend to be very consistent. As are the tools being used - blankets, press, inks, fountain solution etc. Effectively press operators are doing the same job over and over every hour and every day. When you do the same thing over and over you get to know it very well indeed.

So here I have to both agree and disagree. It is true that you get to know the process well - what it can do and what if can't. As for printing always being consistent....

I have run the same ink, same paper and same workflow with different ink coverages and seen totally different results. I rdon't n a heavy solid and the dot gains are super sharp around it....the heavy solid eats up all the water and the ink behaves differently. Then I run a low coverage job thirty minutes later and the gains are crazy high....some inks just don't habdle the change in coverage. Printing is not that consistent job to job depending on the products you run.
 

gordo

Well-known member
So here I have to both agree and disagree. It is true that you get to know the process well - what it can do and what if can't. As for printing always being consistent....

I have run the same ink, same paper and same workflow with different ink coverages and seen totally different results. I rdon't n a heavy solid and the dot gains are super sharp around it....the heavy solid eats up all the water and the ink behaves differently. Then I run a low coverage job thirty minutes later and the gains are crazy high....some inks just don't habdle the change in coverage. Printing is not that consistent job to job depending on the products you run.

So, I agree with you. The inputs to the pressroom tend to be consistent however I didn't say that the printing using those inputs are also consistent.
Your experience is one of the reasons that I don't think that dot gain target and measurements have much value in the pressroom.
 

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