TVI Issue

[Davis.zhou]

We are using Kodak CTP, the plate output is accurate and not need to make linearization.
Printed a IT8/7.4 to build a ICC (attached). For the TVI graph, we found that the C, M, Y curve is not similar to the shape of ISO.
The printed copies looks OK.
Please help to find out is what is the causes of this.
Thanks

 

[gordo]

We are using Kodak CTP, the plate output is accurate and not need to make linearization.
Printed a IT8/7.4 to build a ICC (attached). For the TVI graph, we found that the C, M, Y curve is not similar to the shape of ISO.
The printed copies looks OK.
Please help to find out is what is the causes of this.
Thanks

Assuming that all 4 plates have identical tone values, and these measurements were not taken from a make ready sheet, a live job, or before the press had stabilized, or the press operator was not trying to match a proof...then I think you have a press problem.

You need to look closely (with a microscope) at the dots and solids to start to find out what's wrong - it could be a lot of things as well as different problems for each press unit.

It is not so much that the curve be like the ISO curve. What's important is that the curves nest close to one another (especially the M and C) and all have a similar shape. When that happens you can build plate curves to match the ISO curves.

best, gordon p

 

[The Heidelberg Guy]

Assuming that all 4 plates have identical tone values, and these measurements were not taken from a make ready sheet, a live job, or before the press had stabilized, or the press operator was not trying to match a proof...then I think you have a press problem.

You need to look closely (with a microscope) at the dots and solids to start to find out what's wrong - it could be a lot of things as well as different problems for each press unit.

It is not so much that the curve be like the ISO curve. What's important is that the curves nest close to one another (especially the M and C) and all have a similar shape. When that happens you can build plate curves to match the ISO curves.

best, gordon p

Gordo is right, it looks like a press issue. Could be the ink/water balance, but most likely a press issue.

You need to run a health check on the machine and make sure the machine is sound, then run your tests.

 

[Greg Imhoff]

TVI Issue is in plate or RIP settings - how to fix

TVI Issue is in plate or RIP settings - how to fix

this is most likely a problem in the plate curves or RIP settings because the print results from Highlights into Mid-tones are not in line nor color balanced. The Cyan 25% plate image is printing only 25.3%, Yellow is 28.3%, and Magenta is 33.2%. This is not physically possible due to normal on press pressures from plate to blanket to substrate so I suspect the RIP curves need plate calibration and reset.

Print results in the midtones should be closer in a range ~ 3% for color balance. Black will always be higher than CMY so record and adjust this to be relative following your balanced CMY.

• Recommend you output existing linear plates as is then read and record all CMYK 25, 50; 75 plate images - with a dotmeter prior to press mounting. Print and read your press TVI then apply the net delta curve points needed to correct your plate curves at the RIP to achieve on press color balance. Hope this helps - let me know.

Greg Imhoff
President GRIPdigital & Director EPG Color Solutions
(800) 394 - 7130 - office
(708) 557 - 2021 - cell
Skype: gregimhoff
Print Properties Committee Member and GRACoL G7 Expert
Essex Products Group | Integrated Color Control Systems

 

[gordo]

this is most likely a problem in the plate curves or RIP settings because the print results from Highlights into Mid-tones are not in line nor color balanced. The Cyan 25% plate image is printing only 25.3%, Yellow is 28.3%, and Magenta is 33.2%. This is not physically possible due to normal on press pressures from plate to blanket to substrate so I suspect the RIP curves need plate calibration and reset.
[SNIP]
Recommend you output existing linear plates as is then read and record all CMYK 25, 50; 75 plate images - with a dotmeter prior to press mounting. Print and read your press TVI then apply the net delta curve points needed to correct your plate curves at the RIP to achieve on press color balance. Hope this helps - let me know.

I disagree. Here's why.

What you are suggesting is to build curves to correct a tone reproduction problem that I believe is caused by mechanical problems on the press (as evidenced by the posted dot gain chart).
The key to building plate curves is that you have a mechanically sound plate and press condition because you cannot build curves in an unstable condition.

The OP did not answer my questions about how the press run was carried out, but in his original post he wrote: "We are using Kodak CTP, the plate output is accurate and not need to make linearization."

In fact, for the purposes of tonal calibration, it does not matter whether the plates were linear or not.

What matters first is that the tone step wedges on the plates for each of the process colors are the same. What matters second is that the press is operating in a stable condition and laying down ink correctly.

If those two conditions are met then, if the press (including ink transfer) is running properly, the resulting curves will have a similar shape relative to one another. They may be the wrong shape, but that can be corrected with a plate curve.

Here's an example:

The target tone curve is the dotted red line. Note that the press response curves are the wrong shape, but they all share a similar shape and nest well together.

Compare that press response to the OPs curves:

Here the curves are nowhere near each other in terms of shape, nor do they nest with each other.

Therefore based on the conditions I assumed (the questions he did not answer) the press condition is such that he should not attempt to build plate curves. He needs to find out why he got the tone response he got. Fix those issues first. Then he can look at building curves.

best, gordon p

 

[Greg Imhoff]

TVI is TVI

TVI is TVI

Hi Gordo I was simply offering a quick check / solution with reason. Let me explain.

If the question of plate output quality is unanswered and if the issue needs to be solved my experience is when any 1/4 tone is under-performing as this curve clearly is - then this is a plate calibration issue. This may be proven on press with normal pressures creating mechanical dot gain curves unique to each press condition. This curve set is not logically growing. Until the subject plates are documented linear from a balanced RIP all else seems on the info provided, for naught.

Beginning at the beginning works especially with the dot curves given. What could plate calibration first hurt? Nothing. Help? Everything. Time ~ 30 minutes for all 4 plates.
Yes we agree there could be additional press issues but with a set of known plate values before press we would then quickly see and cure, any press manifested issues. Effectively.

Sincerely,

Greg Imhoff
President GRIPdigital, inc. & Director EPG Color Solutions
(800) 394 - 7130 - office
(708) 557 - 2021 - cell
Skype: gregimhoff
Print Properties Committee Member and GRACoL G7 Expert
Essex Products Group | Integrated Color Control Systems
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[gordo]

Unfortunately the OP hasn't responded to questions to provide more info. So one makes assumptions.

I think that if he is using different applied plate curves for each process color - then maybe he would get the response he's showing and therefore it could be caused by a plate calibration issue.
But that would be an unusual situation - so I doubt it.

If his CtP has imaging inconsistent enough to cause enough tone variation in a 4/C set of plates to cause the kind of press response that he got...well, he's doomed.

If all the plates have the same curve (calibrated or uncalibrated), which is what the OP hinted at ("the plate output is accurate and not need to make linearization") then the press response (the dot gain curves) should be similar, and equally incorrect, for all four colors if the press condition is proper. How could it be otherwise?

You are right, linearizing the plates first won't hurt anything. But it is not required - either for calibration or to determine if there is a press problem. Just because the plates are uncalibrated does not mean that the plate values are unknown - at least by him. After all, he did state: "the plate output is accurate and not need to make linearization". The notion of linearizing plates, I believe, comes from the film days. In a CtP environment, unless you've got some real imaging issues, it's redundant and can cause errors because you are applying two curves - one to make the plate linear, then another to achieve the tone response on press that you are trying to achieve.
As the G7 "How To" says it: "E.4.4 Setting Up a Single-Stage RIP
On Single-Stage RIPs (with only one set of curves) pre-linearization prior to a G7 press run is optional, but not recommended, as the G7 process will effectively over-ride the linearization values, and the linearization curves may interfere with the G7 process, leading to inaccuracy." Again, I'm making another assumption, and that is that this individual is using a "single stage" RIP which is pretty common.

So, as far as I can tell from the information supplied - this is a press problem not a plate calibration problem. A few minutes in the press room with a microscope and spectrodensitometer is in order.

best, gordon p

 

[Davis.zhou]

Dear all,

Sorry for not responding all the follow up posts. I was out of town for few days.
Thanks for all your comments.
The followings are information of our current system:
1. Prinergy Workflow
2. Kodak Trendsetter 800 II (Quantum)
3. G & J Plate Processor
4. Measuring device - Hanna pH meter & conductivity meter, digital thermo-meter, X-Rite IC Plate II
5. Plate - Kodak CTP plate
Plate processor chemical was checked everyday
Ugra digital plate wedge was used for plate quality control, we did not measure the plate screen in each plate, measurement sampling was taken in 1 set of plate (4 color) in 4 sets of output.
Since the Kodak CTP output is accurate, 10% output 10%, 20% output 20%...90% output 90%. We did not apply any plate compensation curve in Harmony.
The previous attached TVI curve was built by Profile Inspector - ColorThink Pro 3.0.
In the press side
1. Heidelberg SM102-4 with CP2000 print control- Y2005
2. Meiji blanket was used
3. fountain solution also checked in daily basis - pH (4.8 - 5.5), conductivity (fresh - 800m/s to 1200m/s, will replace fountain when it reach 1700 m/s), temperature (10 to 12 degree C) and alcohol content (10%).
4. pack gauge was used to check the blanket to cylinder bear and plate to cylinder bear
5. ink roller and fountain roller strips were check in weekly basis

We did not know how to start to find out where is the cause of problem. Hope that anyone of you can provide your valuable comment to educate us to correct this problem.

 

[The Heidelberg Guy]

Dear all,

Sorry for not responding all the follow up posts. I was out of town for few days.
Thanks for all your comments.
The followings are information of our current system:
1. Prinergy Workflow
2. Kodak Trendsetter 800 II (Quantum)
3. G & J Plate Processor
4. Measuring device - Hanna pH meter & conductivity meter, digital thermo-meter, X-Rite IC Plate II
5. Plate - Kodak CTP plate
Plate processor chemical was checked everyday
Ugra digital plate wedge was used for plate quality control, we did not measure the plate screen in each plate, measurement sampling was taken in 1 set of plate (4 color) in 4 sets of output.
Since the Kodak CTP output is accurate, 10% output 10%, 20% output 20%...90% output 90%. We did not apply any plate compensation curve in Harmony.
The previous attached TVI curve was built by Profile Inspector - ColorThink Pro 3.0.
In the press side
1. Heidelberg SM102-4 with CP2000 print control- Y2005
2. Meiji blanket was used
3. fountain solution also checked in daily basis - pH (4.8 - 5.5), conductivity (fresh - 800m/s to 1200m/s, will replace fountain when it reach 1700 m/s), temperature (10 to 12 degree C) and alcohol content (10%).

This seems a little low, I have them running at 4.3 to 4.4 pH, then try cutting your alcohol back to 6%, this might give more of a consistant run. What Fountain Solution are you using? The temp sounds fine for running Alcohol, havent ran alcohol in many years.

4. pack gauge was used to check the blanket to cylinder bear and plate to cylinder bear

Since to didnt publish your specs, the plate must be .006" above bearer, and blanket even to .001" below.

5. ink roller and fountain roller strips were check in weekly basis

Checking stripes on a weekly basis is a little much, every two to three weeks should be sufficiant. What are your stripes to the plate? What are your stripes to the oscillators? Make sure you have NO form roller oscillation on the plate!

We did not know how to start to find out where is the cause of problem. Hope that anyone of you can provide your valuable comment to educate us to correct this problem.

BTW, what are your pre and post damp settings?

 

[Greg Imhoff]

The curve problem is manifesting itself on press and not in your plate calibration settings. I suspect this may be traceable to the the ICC profiled curves recently mentioned. Even though the plate output may be linear a incorrect image curve set may be applied to output of the CMYK images, from the ICC profiles. Process control has logical steps. If applying CMYK curve sets from the ICC profiles I suggest a quick check of the plate image % dot expected to the proof image dot area accepted.

Gordo is correct on the G7 single stage RIP statement. The main reason G7 works (over FTP) is CTP is first generation imaging. We agree CTP imaging is stable however, like any process, each step needs monitoring. I like to begin at the beginning so my advise is compare your proof image highlights to your RIPped plate highlights ... to see what to do next.

Sincerely,

Greg Imhoff
President GRIPdigital, inc. & Director EPG Color Solutions
(800) 394 - 7130 - office
(708) 557 - 2021 - cell
Skype: gregimhoff
Print Properties Committee Member and GRACoL G7 Expert
Essex Products Group | Integrated Color Control Systems (Essex Products Group | Integrated Color Control Systems)

We are using Kodak CTP, the plate output is accurate and not need to make linearization.
Printed a IT8/7.4 to build a ICC (attached). For the TVI graph, we found that the C, M, Y curve is not similar to the shape of ISO.
The printed copies looks OK.
Please help to find out is what is the causes of this.
Thanks

 

[turbotom1052]

going with the assumption that in order to accurately calibrate ctp curves you must start from the press id like to expound a bit on whats been said allready re. preparing the press for this initial test. in addition to all the coments about preparing the press for this test id also suggest the following......
1 pull break away solids on all the printing units to determine not only that your printing with kiss impression between your blanket and impression cylinder but also that your plate to blanket pressure is correct. ive seen presses that may have all the proper plate and blanket heights as measured by a packing gage and still have variations from one side of the press to another. variations like this can skew the results of a test form and you wind up chasing your tail when trying to arrive at your ctp curves. i know that on speedmaster presses there is a mechanical adjustment that can be made to insure that all your cyinders run in perfect parallel with each other.

2 id also encourage that your digital scales and potentiometers are all in sync with each other and accurately portraying the intended "squeeze". to just set all your units on a target point and hope that they all print with the same squeeze from unit to unit might be an assumption that will prove to be costly.

when you consider the amount of time and effort spent arriving at the optimum settings in the prepress dept it only stands to reason that you MUST blueprint the press and eliminate any and all potential variables

 

[vaithi47]

to me it seems like a press problem related to blanket not being tightened properly,or incorrect plate/blanket packings or pressure setting of plate/blanket/impression.make sure that llthese are as per m/c's specifications.most probably you will get the answer