IFRA plate curves

[snrv]

Hi
We have printed the IFRA fingerprint form with Linear plates with standard densities and all others. After that we got Curve from the printed sheet. example for Cyan: 10% on plate is becoming 22.5% on press, 50% on plate is becoming 73.7% on press.
Can u please analyze the attachment and guide me what & how should be the compensate values on plates as per IFRA

 

[Bloodsaler]

Your press is web for newspaper or for the commercial printing?

 

[snrv]

its a News paper Web offset

 

[gordo]

Hi
We have printed the IFRA fingerprint form with Linear plates with standard densities and all others. After that we got Curve from the printed sheet. example for Cyan: 10% on plate is becoming 22.5% on press, 50% on plate is becoming 73.7% on press.
Can u please analyze the attachment and guide me what & how should be the compensate values on plates as per IFRA

Why did you do that? There was no need to linearize the plates first. Now you will have a two curve workflow - with one redundant curve curving a curve. This is explained here:

Quality In Print: Search results for linearize

The principle of building dot gain compensation curves is explained here:

Quality In Print: The principle of dot gain compensation plate curves

best, gordon p

 

[snrv]

hi mr. gardo
Thanks 4 ur detailed reply. suppose i didn't leniarized, if 50% in file comes 73% on plate, how much we need to compensate? pl explain me

 

[gordo]

hi mr. gardo
Thanks 4 ur detailed reply. suppose i didn't leniarized, if 50% in file comes 73% on plate, how much we need to compensate? pl explain me

To build a compensation curve you need:

1- Original % requests - that is the 10% 20% 30% etc. in the original file (illustrator, PDF, InDesign etc.)
2 - A target - that is the % values you want on press at each % in the original file (e.g. for a 50% request in the original file you want to measure 70% on the press sheet)
3 - A press run at your correct solid ink densities in order to measure what tone value you actually get at that requested tone. (e.g. I asked for 50%, my target was 70% but I measured 75% on the press sheet.

From those three pieces of information (requested tone, target tone, and press tone response) you can easily build a compensation to make the 50% request measure 70% on the press sheet.

Note - I did not mention what the tone values on the plate are. That's because it doesn't matter what the plate tone values are. All that matters is that whatever they are they are consistent. That means (assuming that the plate imaging is correctly set up by your vendor) that if I ask for 50% in my file and I get 42% on the plate then every time I ask for 50% I should get the same 42% tone on plate.

Note - I did not mention dot gain values. Dot gain values are variables as they change with screening and density. They are not targets. The target is the tone response that you want on the press sheet. The tone value is an absolute.

I did take the numbers you provided and plotted them to see how well the CMYK curves relate to one another. I'm assuming that you are running to standard newsprint densities and I'm assuming that the press run was good and that you're measuring was correct. If you look at the curves plotted out:

You'll notice that the Yellow and Black have some strange waves in them. That usually suggests a problem that should be investigated before you try to build any compensation curves. If there is a problem and you try to fix it with curves then you will just make the problem worse. I would not build any curves until I had investigated why your press curves have such strange shapes and then fixed the problem.

best, gordon p

 

[Bloodsaler]

We print newspaper too.But we use film for platemaking.For the speed of nowdays CTP is to slow for us.
Actually we didn`t do any compensation curve,only try to catch the right color and right density by operator himself.
For the newspaper surface not stable,so you can`t get a steady dot gain in press run~

 

[gordo]

We print newspaper too.But we use film for platemaking.For the speed of nowdays CTP is to slow for us.
Actually we didn`t do any compensation curve,only try to catch the right color and right density by operator himself.
For the newspaper surface not stable,so you can`t get a steady dot gain in press run~

ISO 12647-3 (coldset newspaper) is based on linear (positive) film. The problem is that linear film does not deliver linear plates. Also, calibrated CtP plates may not be linear. So, to deliver presswork that meets the ISO specification you may need to apply a compensation curve to the plate.

The compensation curve to the plate affects the tone reproduction. Something that the press operator does not really have any control over. The press operator only really has control over solid ink density.

Again, dot gain is not the issue. Tone reproduction is. And newspaper work can be stable enough to achieve the target.

best gordon p

 

[Bloodsaler]

Actually the quality requirement not high for newspaper,as I concern,to do a compensation or not to do also can go on the work~
And doesn`t affect the appearance of the sheet too much~

 

[gordo]

Actually the quality requirement not high for newspaper,as I concern,to do a compensation or not to do also can go on the work~
And doesn`t affect the appearance of the sheet too much~

Hmmm. In my experience the quality requirement for newspaper is actually very high for three reasons:

1) Advertisers who are the ones who pay a great deal of money to have their expensive advertisements reproduced in newspapers expect their art to be properly reproduced.

2) Newspapers are fighting for their lives in this digital world. The cannot afford to be slack in the the quality of their work. It's just too easy for their customers to go to other media.

3) The material they deal with, from original art to inks and paper are usually of substandard quality. Newspaper printers must work much harder to achieve a quality product.

Of course my experience is only with newspapers in North America, Europe and SouthEast Asia and might not apply to all regions of the world.

best, gordon p

 

[snrv]

Hi Mr.Gordo Guru, thankx for ur kind reply.
Suppose assume that after fixing all press problems and printed with standards. i got a curve fingerprint2.jpg. what will be the Plate compensation curve for news paper web offset.

 

[gordo]

Hi Mr.Gordo Guru, thankx for ur kind reply.
Suppose assume that after fixing all press problems and printed with standards. i got a curve fingerprint2.jpg. what will be the Plate compensation curve for news paper web offset.

I am not a guru.

Like I said, your plate compensation begins with your target which you have NOT identified. The plate compensation curve will be based on the points I made in my last post - which you appear to be ignoring.

Is your target SNAP? (Specifications for Newsprint Advertising Production) or ISO 12647-3 (Graphic technology - Process control for the manufacture of half-tone colour separations, proofs and production prints – Part 3: Coldset offset lithography and letterpress on newsprint) or something else?

Next, you provided tone values that are different from the ones you originally posted but you provide no details. No solid ink densities. No lpi. No info as to whether the plates were run linear or unlinearized. Why are these values different from your last post?

I plotted these new values and now your curves look quite good:

What did you change from your last post? Why are these numbers different?

You have already been given all the information you need to answer your question. Read the information you've been given including the blog links. If you still don't understand then ask a specific question.


best, gordon p