UCR using ICC color Profiles

[Nutech Shroff]

Hello,

We are commercial Printer and get ready to Print PDF files. We would like to use UCR on the files received from the customer. I wanted to know if we can apply a UCR enabled ICC Profile in the RIP (True Flow from Screen) or we would have to install in softwares such as GMG or CMS server to achieve this.

Thanks

 

[Repro79]

Basically it depends from Color Management possibilities in the Rip (and these possibilities depends from APPE "core" version). But if I remember everything right TrueFlow don't have such possibilties at all may be in Equios (current version of Screen so called "workflow")

 

[Stephen Marsh]

If you really wish to successfully go down this path you will likely need to consider using a Devicelink ICC Profile based workflow, not just a standard Device ICC profile (if reseparating text, vectors and raster images). If you are only reseparating raster images, then you could probably just get away with using a standard Device ICC profile.

In addition to all of the standard 3rd party “Colour Server” based methods or a method provided from your prepress workflow vendor, I would also suggest that Enfocus PitStop Server can be configured to be a very capable automated hot folder based “colour server” in addition to providing preflight and file correction.


Stephen Marsh

 

[gordo]

Why do you want to use UCR separations?

 

[Nutech Shroff]

Why do you want to use UCR separations?

Mainly for Higher Color Stability Thru the Press Run

 

[Stephen Marsh]

I didn’t wish to muddy the water with the whole UCR vs. GCR thing in my previous reply, however Gordo is of course correct in bringing this up… It is not very often that we hear people wishing to use UCR in this day and age!


https://en.wikipedia.org/wiki/Grey_component_replacement

https://en.wikipedia.org/wiki/Under_color_removal

UCR and GCR WHAT ARE THEY? - Sun Chemical



Stephen Marsh

 

[gordo]

Mainly for Higher Color Stability Thru the Press Run

I'm afraid you are misinformed. A UCR separation is much, much less stable on press than a GCR separation.

 

[aqazi81]

Whats the difference between GCR and some ink optimization software like GMG Ink Optimizer?

 

[gordo]

Whats the difference between GCR and some ink optimization software like GMG Ink Optimizer?

It's GCR using device link profiles - CMYK in - CMYK out - without going through Lab. Each vendor of ink optimizing software does this however there can be subtle (and sometimes not) differences in the results. The most common issue is shade stepping and contamination of single channel colors. You can see how the different vendor results compare here: https://www.idealliance.org/product/ink-optimization-roundup-2010-results-report/

 

[Stephen Marsh]

More info:

http://the-print-guide.blogspot.com....vings-and.html

https://www.pfmediatech.com/files/nl...whitepaper.pdf

http://www.kodak.com/KodakGCG/uploadedFiles/WP_ink_optimizing_727-00215A-EN.PDF


Stephen Marsh

 

[ddonevski]

I'm not sure if I understood Your question correctly. I suppose You are commonly using some ICC profile (custom or standard) which characterizes your printing process. ICC profiles already use UCR or GCR to some extent. The thing is, we only need three variables (CIE L*a*b* or XYZ) to specify the color, but we have four inks at our disposal. The presence of K, in addition to the ability to render dark colors not obtainable by CMY alone, also provides the ability to replace some of the CMY combinations (gray component present in them) with K.
So let's dissect this:
ICC profile - has A2B (CMYK -> CIE L*a*b*) and B2A (L*a*b* -> CMYK) tables for three rendering intents (0 perceptual, 1 relative colorimetric, and 2 saturation). A2B tables (CMYK -> L*a*b*) have CMYK inputs from 0 0 0 0 all the way up to 100 100 100 100, and CIE L*a*b* as their corresponding outputs. On the opposite, B2A tables (CIE L*a*b* -> CMYK) will never result in 100 100 100 100 CMYK output. They employ the total ink limit (TIL) also called total area coverage (TAC) and UCR or GCR.
UCR - Under color removal, is a subset of GCR. Basically, it only applies GCR in near-neutral colors.
GCR - Gray component replacement - in addition to near-neutrals, it also applies gray component replacement to more saturated colors.

ICC profiles already employ some UCR/GCR algorithm to some extent. If You want take reseparate this (CMYK standard profile -> CMYK new) to make use of unused GCR potential, i.e. save ink and increase press stability, you need to use some ink optimization software. While many of those are static and use device links (CMYK old -> CMYK new), some apply GCR depending on content (dynamic solutions) in order to avoid the appearance of visible artifacts such as banding, contouring, and graininess. Recently, I wrote a short article about this, see https://medium.com/@ddonevski/why-in...e-931eb738c674

 

[gordo]

UCR - Under color removal, is a subset of GCR. Basically, it only applies GCR in near-neutral colors.
GCR - Gray component replacement - in addition to near-neutrals, it also applies gray component replacement to more saturated colors.

That's not quite correct.
UCR (Under color removal) and GCR (Gray component replacement) are basically the same (RGB to CMYK transformations). Where they differ is how far away from absolute neutrals in the original image they introduce Black. GCR doesn't just apply to more saturated colors. It applies wherever the 3 chromatic (CMY) colors print together.

When three chromatic colors appear together the third color effectively desaturates the hue of the combination of the other two inks. I.e. If C,M,Y appear together to form a color then the C or M or Y will desaturate the hue of the other two. It greys the color. So one can replace the greying of that third color by using an achromatic color - Black - since the Black has the same greying effect as that third chromatic ink (C, or M, or Y). Hence Grey component replacement.

GCR can therefore technically be applied anytime the three chromatic colors appear together - from light pastels to fully saturated colors not just the saturated colors. You may not want to do that, i.e. apply it to very light pastels, but you can certainly do so.

 

[ddonevski]

UCR (Under color removal) and GCR (Gray component replacement) are basically the same (RGB to CMYK transformations). Where they differ is how far away from absolute neutrals in the original image they introduce Black. GCR doesn't just apply to more saturated colors. It applies wherever the 3 chromatic (CMY) colors print together.

How does this contradict my statement? We agree that they (UCR and GCR) differ in how far from absolute neutrals they introduce Black. UCR operates in near neutrals and is therefore a subset of GCR. GCR takes it (in addition to near-neutrals) a little further and applies black farther from near-neutrals, or as You stated, "It applies wherever the 3 chromatic (CMY) colors print together.".

I can't see any disagreement between our statements.

 

[Nutech Shroff]

Thanks for all the inputs.

 

[Nutech Shroff]

Hello,

We are commercial Printer and get ready to Print PDF files. We would like to use UCR on the files received from the customer I wanted to know if we can apply a UCR enabled ICC Profile in the RIP (True Flow from Screen) or we would have to install in softwares such as GMG or CMS server to achieve this.

Thanks

I must apologise - I meant GCR and not UCR. All the profiles that I have been experimenting with are GCR.

 

[ddonevski]

What do You mean by profiles You have been experimenting with? An ICC profile characterizes a given printing process. There exist standard ICC profiles, which can be applied to printing processes aligned to ISO 12647 family of standards, Gracol or SWOP specifications, and so on. If your process is aligned to some standard such as ISO 12647, you can use the standard profile which characterizes it as well as the process is aligned to the norm. If your process isn't aligned to some standard, it can be characterized by its custom ICC profile. An ICC profile characterizes a given process, i.e. it links CMYK and CIE L*a*b* for a particular combination of inks, substrate and printing press. The use of standard profiles presumes the use of inks conforming to ISO 2846 norm, paper conforming to one of the ISO Type 1-5, and press aligned to some (e.g. ISO 12647) norm aims. Experimenting with different profiles for one printing process isn't right because each profile is meant to characterize the process it was created for.

 

[arossetti]

I think he means he is experimenting with different device output profiles for his printer.

 

[ddonevski]

I think he means he is experimenting with different device output profiles for his printer.

Okay, but profiles are meant to describe the behavior of one particular process (printer/press, substrate and ink). Applying different profiles to one printing process does not make sense since profiles are meant to characterize particular processes. For example, for a given aimed CIE L*a*b*, ISO Coated and ISO Uncoted Yellowish profiles will provide different CMYK recipes because those two processes (one using coated bluish paper, and one using yellowish paper) will require different CMYK inputs in order to achieve the same color, precisely quantified in CIE L*a*b* coordinates.
Applying different profiles to one printing process is the exact opposite of the intended use. Applying different profiles to one printing process will give you different CMYK recipes for given aimed CIE L*a*b*, and non of them will achieve the aim since non of the profiles actually characterizes the given process.

 

[arossetti]

So I can't speak for OP but what it sounds like is he has created several profiles for one press/ink/paper combo testing out different baked in GCR settings. I experiment all the time with creating different profiles for the same press/ink/media to see if I can get the same visual results while saving ink.

 

[Nutech Shroff]

What do You mean by profiles You have been experimenting with? An ICC profile characterizes a given printing process. There exist standard ICC profiles, which can be applied to printing processes aligned to ISO 12647 family of standards, Gracol or SWOP specifications, and so on. If your process is aligned to some standard such as ISO 12647, you can use the standard profile which characterizes it as well as the process is aligned to the norm. If your process isn't aligned to some standard, it can be characterized by its custom ICC profile. An ICC profile characterizes a given process, i.e. it links CMYK and CIE L*a*b* for a particular combination of inks, substrate and printing press. The use of standard profiles presumes the use of inks conforming to ISO 2846 norm, paper conforming to one of the ISO Type 1-5, and press aligned to some (e.g. ISO 12647) norm aims. Experimenting with different profiles for one printing process isn't right because each profile is meant to characterize the process it was created for.

I have been trying out ICC Profiles based on Different paper types and Different levels of GCR.