Is linear plates more important that backward compatibility with TVI curves?

[gordo]

Lukas,

I have never made PSO or G7 curves from a non-linear plate. It's hard to imagine a 50% dot being harder to control one way or the other. Currently I am not able to identify problems related to using linear plates, however in the past, when using a Fuji Saber (violet) I used to get strange negative dot gain in the highlights after a G7 set-up, particularly in the black channel; I never diagnosed the cause of that but always felt it was related to plate linearization. We print at 175 lpi. As a Rampage user I must use 25 fulcrum points so after setting up one CTP device and one press (lin+c+m+y+k) I am using 125 fulcrum points.

I understand the math simplicity argument for uncalibrated plates, however, a case can be made for whatever conditions require the least amount of correction would be best. Because I maintain curves for 4 platesetters and 14 curve sets and cannot identify a quality compromise with linear plates, my preference is for linear plates; otherwise I would have (4*14) 56 tone curves (or [56*25] 1400 fulcrum points) and each time I updated one set I would have to update three more.

In the US I would contact someone in the IDEAlliance Print Properties group who serves as a technical committee for ISO input for the print stuff.

Matt Louis

As a general statement, at 175 lpi - linear plates will give you a result that is very close to traditional sheetfed offset tone reproduction (i.e. dot gain). So the curve to make the plate linear from its natural state in effect is a dot gain compensation curve. The curve doesn't have to make the plate linear but in the case of 175 lpi it so happens that that is the appropriate curve. However, if you change screening (e.g. use FM or higher or lower lpi AM/XM) or use a different substrate, then linear plates will not give you the correct tone reproduction (i.e. too much dot gain). In that case, you will need to create a plate curve that will result in the correct tone reproduction in your presswork. Your plates will no longer be linear.

The problem with arbitrarily using linear plates is that you cannot normalize tone reproduction across different screening technologies or substrates. If the goal for a standards organization is to normalize tone reproduction then there should be just one presswork tone curve that all printers should strive to achieve using whatever curves are needed to do so.

PS in a CtP workflow, calibrating plates is not making them linear. Calibrating the plate means adjusting exposure and processing in order to achieve a consistent, robust, image on the plate that will carry ink where needed and not where not needed. Once the plate is calibrated then a curve may be applied in order to achieve the required tone reproduction on press. That curve may or may not make the plate linear.

best, gordo

[mglouis]

Green Printer,

The 50 patch was the example used to initiate discussion. It's kind of a big deal on press But I understand your point. Being 2% off in a highlight is a bigger problem than in the mid-tone.

Our Fuji techs aren't really into tweaking exposure for the sake of hitting a 50% dot -- something something about laser life. We agreed to let them do their thing as we do ours. In any case, unless every CTP device has the same native curve then press tone management increases in complexity with each additional device.

If I may echo @chevalier, stability is king.

- Matt Louis

[mglouis]

Gordo,

Your statement supports IDEAlliances's claim that the reference NPDC shape was based on uncalibrated CTP (for 175 lpi). I would like to see ISO12647-2 adopt G7 NPDC and substrate relatively for gray balance and ink solids + overprints then let printers lean on FOGRA, IDEAlliance or whomever for print specifications as often as suitable. This relativity part should prevent ISO documents for graphic arts from becoming outdated as quickly as they have in the past.

Matt Louis

[gordo]

Gordo,

Your statement supports IDEAlliances's claim that the reference NPDC shape was based on uncalibrated CTP (for 175 lpi). [SNIP]

Matt Louis

The CTPs were calibrated (Creo Trendsetters). No curve was applied to make them linear (at least, AFAIK, after the first run at LA Graphico). However, the Creo Trendsetter/plate combinations that were used happen to result in virtually linear plates. Not all CtP/plate combinations do so.

best, gordo

[Paul Santer]

When a printing plate is developed, how should it respond to optimum CTP and processor settings from a linear file?

[Tommyjt]

Why shouldn't one linearize plates first? I recall two particular scenarios where it has been a benefit. One was when Kodak changed our plate processor developer temperature and developing time. That changed our dot on plates. The other was when they changed the laser intensity and that also changed the dot. In these two cases all I had to do was change the linearization curve and we were ready to roll.
To see those whom I have respect for call this "idiotic" makes me wonder if I'm missing something here.
Convince me that it is "pointless."

Regards

[gordo]

Why shouldn't one linearize plates first? I recall two particular scenarios where it has been a benefit. One was when Kodak changed our plate processor developer temperature and developing time. That changed our dot on plates. The other was when they changed the laser intensity and that also changed the dot. In these two cases all I had to do was change the linearization curve and we were ready to roll.
To see those whom I have respect for call this "idiotic" makes me wonder if I'm missing something here.
Convince me that it is "pointless."

Regards

OK, to use your example: "In these two cases all I had to do was change the linearization curve and we were ready to roll."

Correct. But if you didn't use a linearizing curve first then you could have written:
"In these two cases all I had to do was change the plate curve and we were ready to roll"

Using two curves, one to linearize and another to get the right tones on press doesn't gain you anything but complexity, a greater chance of making a mistake, as well as the potential for banding/shade stepping.
I'll grant that in a few cases, doing a linearization first is the way to go. However for the vast majority of printshops that step is redundant.

Best, gordo

[Ozkan Hangisi]

Why shouldn't one linearize plates first? I recall two particular scenarios where it has been a benefit. One was when Kodak changed our plate processor developer temperature and developing time. That changed our dot on plates. The other was when they changed the laser intensity and that also changed the dot. In these two cases all I had to do was change the linearization curve and we were ready to roll.
To see those whom I have respect for call this "idiotic" makes me wonder if I'm missing something here.

Convince me that it is "pointless."

Regards

Let me try acording to your scenarios Your dot gains were in tolerance. Then you changed developer parameters or laser power etc. Why do you think re-linerazition will provide same dot gains on the print ? You changed surface&emission referance of plate. It effects ink-water balance, dot endurance etc. After such scenarios, I would check just dot gains on print then modify print curves if necessery. Using lineraziton curve provides no advantage in you cases.

[BillJ]

I only linearize on systems that are being used for non-color managed shops. I learned long ago that applying multiple curves will make you chase your tail.

[Ozkan Hangisi]

I only linearize on systems that are being used for non-color managed shops. I learned long ago that applying multiple curves will make you chase your tail.

It is not chasing tail but standart. On the otherhand working with lineer plates is not that bad, as long as sky is blue, tree is green, repeat jobs are stable and none of your customers is asking for print standart.

Regards
Ozkan