Linerize or not to Linerize plates... that is the question

gordo

Well-known member
I think that in some unique situations I agree. Which is why in my original post I said:

"in the vast majority of cases a curve to linearize the plate before applying a second, dot gain compensation curve, is redundant and adds complexity without benefit. That being said, in a few cases, typically multi- site operations, a two curve workflow can be appropriate."

My argument being that the shop needs to think it through and not just go the linearization first based on just assuming that's what is correct.
 

Slammer

Well-known member
With processless plates becoming more and more prevalent a two curve solution with a plate curve and a press curve is difficult if not impossible to implement in any meaningful way. In this case I would say that if the optical output of the CTP is within tolerance I would rely on the CTP to give me linear plates.
 

Alois Senefelder

Well-known member
Gentlemen of the Pre- Press Brigade,


"Raison d'etre" ...... is to produce - Production Compliant Imaged Lithographic Printing Plates.

Instead of talking endlessly among yourselves !!!



Regards, Alois
 

Jbarrie5

Member
Thanks guys for all your thoughtful opinions. I feared this question might create a divided house, and... after reading all your suggestions and questioning other sources I have landed on the opinion of conducting my next G7 certifications without a linear curve.
Two points that convinced me that this might be the best solution are:
1) In a AM screening environment, the image setter outputs plates somewhat close to Linear(50% images around a 47%), but... in a FM environment, the 50% dot images as a 43%. If going with a Linear curve first, I would have to bring up the dot's considerably (7%)... then remove them again for the press compensation curve, thus... creating a even steeper curve than I feel necessary. Such a steep curve might be more difficult to control and create extra complications while on press.
2) If I use my raw plate readings as a baseline, and apply only 1 curve on top of it (press compensa tion curve) then... if the laser weakens or plate lots emulation changes considerably, I can easily apply an additional curve to adjust the baseline back to my benchmark (hopefully the platesetter is more stable than that, and this won't happen). Using this logic... this backup plan would even satisfy the concern about the platesetters stability.
I hope this action works for me and that everyone else gained some additional information from this feed.

Thanks!
 

Alois Senefelder

Well-known member
Hello Jbarries,


Enlightenment ! The Coating on Litho Plates are composed of "Thermosetting Photopolymers " these form the Image areas of the plates when exposed to lasers used on CtP Imagesetters.


They are NOT emulsions. !


Regards, Alois
 

gordo

Well-known member
Thanks guys for all your thoughtful opinions. I feared this question might create a divided house, and... after reading all your suggestions and questioning other sources I have landed on the opinion of conducting my next G7 certifications without a linear curve.
Two points that convinced me that this might be the best solution are:
1) In a AM screening environment, the image setter outputs plates somewhat close to Linear(50% images around a 47%), but... in a FM environment, the 50% dot images as a 43%. If going with a Linear curve first, I would have to bring up the dot's considerably (7%)... then remove them again for the press compensation curve, thus... creating a even steeper curve than I feel necessary. Such a steep curve might be more difficult to control and create extra complications while on press.
2) If I use my raw plate readings as a baseline, and apply only 1 curve on top of it (press compensa tion curve) then... if the laser weakens or plate lots emulation changes considerably, I can easily apply an additional curve to adjust the baseline back to my benchmark (hopefully the platesetter is more stable than that, and this won't happen). Using this logic... this backup plan would even satisfy the concern about the platesetters stability.
I hope this action works for me and that everyone else gained some additional information from this feed.

Thanks!
Two things:

1 A two curve workflow can introduce tone stepping /banding
2 If the plate imaging changes you don’t have to apply a curve on top of the one you’re using. Just modify the one you’re using.
 

gordo

Well-known member
Food for thought. Years ago we had a laser die in our CTP. We were down a couple days to replace. Because we were using a linear curve and a press curve, I was able to linearize and start making plates to get the presses running without having to do any press tests. Granted Lasers do not die often, but I like the linear curve method.
With a one curve workflow you don’t have to run a press test if, as in your example, your laser dies. You’d do basically the same as you did - apply a curve to bring the plate to the same tone response you had before. That’s what you did when you linearized your plate (before you applied your second curve) it’s just a press curve rather than a linearizing curve (prior to a second curve).
 

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