printing with out dotgain

[maks]

is it possible to print conventional on a six-color press with very minimal dotgain? i shifted to linear plates (50 on file is 50 on plate and print), my concern is when we try to match jobs printed on other printers, majority of our print is lighter compared to the reference supplied. will i try to adjust the plate compensation going up so i can print on the standard dot gain or is there something i need to fix on my press settings. thank you for the available inputs you can share

 

[gordo]

is it possible to print conventional on a six-color press with very minimal dotgain? i shifted to linear plates (50 on file is 50 on plate and print), my concern is when we try to match jobs printed on other printers, majority of our print is lighter compared to the reference supplied. will i try to adjust the plate compensation going up so i can print on the standard dot gain or is there something i need to fix on my press settings. thank you for the available inputs you can share

This is a common misunderstanding - even within print standards organizations.

It's a big topic, but, briefly, "dot gain" should not be considered a target. Tone reproduction is. Plate curves are used to align tone reproduction in press work to a standard (industry or shop specific). It does not matter what the tone on the plate is. What matters is that the plate tones are consistent and that they deliver the target tone in the press work.
It's not good practice to try and adjust "dot gain" or tones in pressork by adjusting the press. That is not what the press is designed to do. The press is specifically designed to lay down a film of ink at a target ink film thickness. That's it.
So confirm your plate imaging is consistent, Define target SIDs. Determine what your target tone reproduction in press work is then build plate curves to achieve your presswork target tone reproduction.
If 50 on file is 50 on plate and print your presswork will look washed out and your printing will have problems.

 

[SteveSuffRIT]

Do NOT adjust press settings (packing, pressures) or materials (ink) to adjust dot gain to visually match an old/legacy proof or previously printed sample (target).
Prepress calibration or plate tone curves achieve the match (accuracy).
The press then tries to replicate and reproduce the same conditions used during the calibration or fingerprint (consistency). This is process control.

 

[maks]

thank you for the inputs. will this mean, if my file is 50%, my plate reading is 50% and my print result is 54%, and i am trying to target my 50% file and plate comes out 64% on print, what i need to compensate is my ctp rip which may mean that my plate profile for 50% is increased to around 58% or 60% to have a resulting 64% print for 50% halftone. waiting for expert advise. thanks

 

[gordo]

thank you for the inputs. will this mean, if my file is 50%, my plate reading is 50% and my print result is 54%, and i am trying to target my 50% file and plate comes out 64% on print, what i need to compensate is my ctp rip which may mean that my plate profile for 50% is increased to around 58% or 60% to have a resulting 64% print for 50% halftone. waiting for expert advise. thanks

If your file requests 50% and the plate measures 50% and the presswork measures 64% then you create a plate curve that makes the plate measure a lower value - e.g. 50% on plate is now 40% on plate. With press dot gain the 40% plate dot becomes a 50% on presswork.

The remaining question is why on earth would you make your print linear.

 

[maks]

If your file requests 50% and the plate measures 50% and the presswork measures 64% then you create a plate curve that makes the plate measure a lower value - e.g. 50% on plate is now 40% on plate. With press dot gain the 40% plate dot becomes a 50% on presswork.

The remaining question is why on earth would you make your print linear.

hope to make this clearer. i can not create a bump curve because my printing is low on dot gain already so i went to use a linear one. but even using linear my print still lacks the desired dot gain. i want my 50% to meet the 64% dotgain when printed - so do i need to increase my plate curve to compensate for this apparent dot loss?

 

[gordo]

hope to make this clearer. i can not create a bump curve because my printing is low on dot gain already

Having low dot gain on press does not stop you from making a plate curve

so i went to use a linear one. but even using linear my print still lacks the desired dot gain.
i want my 50% to meet the 64% dotgain when printed - so do i need to increase my plate curve to compensate for this apparent dot loss?

You seem confused - or maybe there's a language problem? When you say "I want my 50% to meet the 64% dotgain when printed" what you actually want is 14% dot gain {50 + 14 is 64)

Forget linear. Erase it from your mind.

This link explains the process of building curves - read it then come back and ask questions. The principle of dot gain compensation plate curves

 

[maks]

Having low dot gain on press does not stop you from making a plate curve


You seem confused - or maybe there's a language problem? When you say "I want my 50% to meet the 64% dotgain when printed" what you actually want is 14% dot gain {50 + 14 is 64)

Forget linear. Erase it from your mind.

This link explains the process of building curves - read it then come back and ask questions. The principle of dot gain compensation plate curves

thanks for the info. yes, going back to the original queery - i want my 50 to come out 64 (i am getting a measure of 52 now) which means instead of ripping the plate output to apply dotgain compensation, i need to increase the plate curve because of the dotloss. thanks

 

[Magnus]

This would be my advice - step-by-step:

1. Linearize your CTP (so that a 50 % patch in your file reads 50 % on the plate):
a. Expose a step wedge and measure the plate.
b. From this, generate your CTP linearization curve that you assign to your RIP.

2. Run a print-control form:
a. Print a press test chart using the newly linearized plates and your target Solid Ink Densities (SIDs).
b. Measure the printed chart and create a TVI-compensation curve (often called a “dot-gain curve”) this brings your press output aligned to your desired target. You can refine this step with tools like Curve7 or PressSign.
c. Apply your dot-gain curve to your RIP.

When you RIP/rasterize your artwork from now on, you’ll be applying two curves: one for CTP linearization and one for dot-gain compensation.

Add process-control:
a. Preform regular CTP linearization checks and re-linearize whenever your 50 % patch drifts from spec.
b. Monitor on-press dot gain; update your dot-gain curve (or hardware variable) as soon as it shifts out of tolerance.

By establishing—and maintaining—both plate linearity and on-press dot-gain control, you’ll have a solid foundation for consistent, high-quality printing.

 

[SheetSqueezer]

Recommend before performing step #2 above;
Establish correct ink densities at press (by measuring Lab values) before making any printed dot compensation curves.

 

[SteveSuffRIT]

Being a long-term reader, I can predict in advance that "Gordo" is going to say the plate linearization step is unnecessary.

 

[SteveSuffRIT]

Yes, determine/correlate SID (Solid Ink Density) to CIE Lab targets.
If coating inline, this almost negates any dry back/down effects.
If not, dry back/down is about -1 Y, -2 C, -4 M, -15 K on gloss coated paper.
So compensate by adding back into the wet SID.

 

[Magnus]

Being a long-term reader, I can predict in advance that "Gordo" is going to say the plate linearization step is unnecessary.

The advantage of plate linearization is that it simplifies the process of identifying potential sources of deviation when inconsistencies occur. Without clear evidence that the plates are stable and well-controlled, it’s easy for a press operator to blame the plates instead of taking responsibility for the variables they themselves can influence.

 

[gordo]

Being a long-term reader, I can predict in advance that "Gordo" is going to say the plate linearization step is unnecessary.

LOL - am I that predictable? ROTFL

The key criteria is to make sure to set laser exposure and processing (or lack thereof) to the manufacturer's specifications so that the result is a robust halftone dot on the plate that maintains its integrity on press.the plate will have a characteristic non-linear tone response. And that's fine - as long as the plate responds the same - i.e. delivers the same non-linear tone response – every time because without that consistency it is not possible to build any tone reproduction curves at all.
Typically it is the CtP vendor's responsibility to set the laser exposure and processing. That is "calibration" - putting the CtP in a known condition.

To Magnus's point:
Magnus wrote: "The advantage of plate linearization is that it simplifies the process of identifying potential sources of deviation when inconsistencies occur."

It does not simplify a process by adding another (unnecessary) step. It does add complication and another potential for error.

Magnus wrote: "Without clear evidence that the plates are stable and well-controlled, it’s easy for a press operator to blame the plates instead of taking responsibility for the variables they themselves can influence."

The evidence for the pressoperator is that the dot values on plate are as specified and correct and consistent - not whether a curve was applied on top of a curve.

IdeaAlliance is the organization that establishes standards in N America (similar to FOGRA in Europe. As IdeaAlliance finally understood for their G7 process:

And I quote:

"6.2 Origin of NPDC curves
To determine the 'natural' NPDC curves of commercial CtP-based printing, G7 research analyzed numerous press runs made with ISO-standard ink and paper, and a variety of plate types imaged on “un-calibrated” CtP systems (no RIP curves applied, not even to “linearize” the plate).

5.4 Set up the RIP
Set up the plate making RIP exactly as you would for a normal job, but clear out any values in the current calibration table, or begin with a new, empty table. The first press run is best made with ‘un-calibrated’ plates – i.e. no calibration values in the RIP.
IMPORTANT: Do NOT linearize the plate-setter so that measured dot values on plate exactly match original file percentages. Contrary to common belief, this may reduce accuracy of subsequent steps."

SteveSuffRIT wrote: "determine/correlate SID (Solid Ink Density) to CIE Lab targets."

A printing press is NOT engineered/desined to print color. It is engineered to lay down a film of ink onto a substrate. In simple terms, offset lithography is a mechanical process that requires that the ink film layed down achieves a specific thickness on press otherwise the process fails. That ink film thickness is indirectly measured by a densitometer/spectrophotometer. That is what "Solid Ink Density" means.

When the correct ink film thickness (SID) is achieved - the solid ink color can be measured with a spectrophotometer and its Lab value should align with whatever standard/specification you have targeted. For one example: when the SID of Cyan is 1.40 the Lab value should be L 55, a -37 b -50.

So, if you have read this far... what are your target SIDs?

 

[Magnus]

To Magnus's point:
Magnus wrote: "The advantage of plate linearization is that it simplifies the process of identifying potential sources of deviation when inconsistencies occur."

It does not simplify a process by adding another (unnecessary) step. It does add complication and another potential for error.

Magnus wrote: "Without clear evidence that the plates are stable and well-controlled, it’s easy for a press operator to blame the plates instead of taking responsibility for the variables they themselves can influence."

The evidence for the pressoperator is that the dot values on plate are as specified and correct and consistent - not whether a curve was applied on top of a curve.

I understand the points raised in this discussion. Given the reasons mentioned, I agree that it's possible to skip the CTP linearization step. However, if you choose to do so, it's even more critical to establish and document the specific characteristics of your CTP. This documentation serves as a reference point for troubleshooting whenever there are doubts.
Over the years I've encountered many CTP systems that are unable to consistently produce stable plates over time due to a variety of factors. It's important to monitor and control this variable. Without a linearization curve, you're entirely dependent on the CTP vendor to correct any deviations that may occur.

 

[gordo]

I agree that it's possible to skip the CTP linearization step. However, if you choose to do so, it's even more critical to establish and document the specific characteristics of your CTP. This documentation serves as a reference point for troubleshooting whenever there are doubts.

GP: You should be doing that in any case.

Over the years I've encountered many CTP systems that are unable to consistently produce stable plates over time due to a variety of factors. It's important to monitor and control this variable.

Absolutely. That being said, if your plate imaging is not stable/consistent then building any curve is an exercise in frustration.

A Without a linearization curve,

B you're entirely dependent on the CTP vendor to correct any deviations that may occur.

I respectfully disagree. The CtP vendor's job is to set up the plate imaging correctly - not to manage plate curves.
A linearization curve is irrelevant.
B does not follow A
If plate imaging is not consistent then building curves is not possible.

 

[Magnus]

If plate imaging is not consistent then building curves is not possible.

Scenario: Something has changed, and it's affecting the exposure of the plates. Your plate verification measurements have deviated from the set tolerances. What do you do?

A. Stop all production until the CTP vendor has a technician at your site.
B. Send faulty plates to the printer and keep your fingers crossed that the customer won't notice.
C. Adjust a linearization curve in the RIP and continue providing the printer with consistent plates (until the technician has corrected the initial problem causing the deviation).

 

[chriscozi]

Scenario: Something has changed, and it's affecting the exposure of the plates. Your plate verification measurements have deviated from the set tolerances. What do you do?

A. Stop all production until the CTP vendor has a technician at your site.
B. Send faulty plates to the printer and keep your fingers crossed that the customer won't notice.
C. Adjust a linearization curve in the RIP and continue providing the printer with consistent plates (until the technician has corrected the initial problem causing the deviation).

D. None of the above.
"Your plate verification measurements have deviated from the set tolerances."
If there is a flaw in the plate production process and you don't have internal control/repair options for that process why/how are you measuring it?
- Over and over the production manager who didn't understand the process said 'linearize the plates'
- Over and over the problem was on the press. ONE time there was a chemistry issue which was obvious on inspection.
We never did re-linearize the CTP.

 

[Magnus]

D. None of the above.
"Your plate verification measurements have deviated from the set tolerances."
If there is a flaw in the plate production process and you don't have internal control/repair options for that process why/how are you measuring it?
- Over and over the production manager who didn't understand the process said 'linearize the plates'
- Over and over the problem was on the press. ONE time there was a chemistry issue which was obvious on inspection.
We never did re-linearize the CTP.

I don’t understand the logic behind your arguments here. ”If you cannot fix it in house don’t measure it?” Please explain what you suggest for option D.

 

[chriscozi]

I don’t understand the logic behind your arguments here. ”If you cannot fix it in house don’t measure it?” Please explain what you suggest for option D.

Ah yes. The opposite of the statement I made. I implied that 'If you are measuring it then you should be able to fix it' and stated 'if you CAN'T fix and are measuring it then why are you measuring it ?'

In plain english I never implied you 'shouldn't measure if you can't fix it.'
Thats some twisted logic right there.
I could even get behind measuring just for the sake of being able to tell the press folk (Which I am/was one of) - 'See - it's spot on." (snark intended) regardless of your ability to fix it.

I think it is extremely likely that anyone who has the skill set and training (hmm, I've trained a few) to measure the dots on a plate WOULD and SHOULD have at least a passing knowledge of WHAT makes dots on plates change and how to fix it.
Worst case - try a new box of plates.

And then there's always a chance at a new job someplace else . . . .
lol