Forenindex » PrePress allgemein » CMS (Color-Management) » spotcolors & tonal curves

spotcolors & tonal curves

Meister Propper
Beiträge gesamt: 1313

7. Sep 2012, 07:23

gelesen: 651

Beitrag als Lesezeichen
hier ein interessanter auszug von einem diskussionsforum in linkedin. ich fande es ganz interessant:

Zitat Question: I liked to hear from anyone who has experience of updating tonal curves for spot colors in their RIP workflow. What problems have you experienced and have you resolved the issue.

Zitat Answer: Some of my research may or may not be relevant to your question. I did a TAGA paper last spring on tone value increase. My colleague and I (Pat Noffke) developed a model that explained the color (spectra or CIELAB) of a C, M, Y, or K halftone, and applied it to web offset (with data from two continents), newsprint (two continents), flexo, and gravure (again two continents).

Our research says that halftones can be characterized by how much the dots squish out. At one extreme, the dots have the same ink film thickness as the solids, and the Murray-Davies formula applies at a wavelength by wavelength basis. At the extreme end, the dots become a continuous tone that is not as thick as the solid. Beer's law then applies. All printing that we could find can be characterized by how much the dots squish out, so a mixture of the two formulas can predict halftones for all printing..

There are some things here that challenge conventional wisdom. There was no need to invoke "dot gain" as we know it, just how far the dots squished out. Stochastic printing does not have higher dot gain because there is more ink. There is a richer color for the same dot area on the plate simply because the ink is used more efficiently.

Depending on how far the dots squish out, you get a different tone value trajectory in CIELAB. So, adjusting plate curves has limited benefit if you are trying to match stochastic to conventional, or web offset to gravure.

Given that it worked so well for so many different types of printing, I expect that the technique would work well for halftones of specialty colors as well.

Is this along the line of your question, or does your question have more to do with the workflow and specific software?