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ColoR ManaGeMenT In THeGRaPHIC aRTsHarlequin® RIP solutions

IntroductionColor printing using a printing press has been around for slightly over 100 years

using a variety of techniques from stones and grease pencils to films and plates to

more recently using “digital” processes for page design, imaging and plate making.

We see color because of the RGB sensitive cones in our eyes and sophisticated

processing in our brains. To observe color there must be a light source, an object

that the light source is illuminating and an observer that is viewing the object. The

color of light is defined in terms such as wavelengths and radiation whereby

different wavelengths produce different colors within the human visual spectrum.

The term color management has recently been used to describe the digital

transforms from different color spaces in the digital revolution. In actuality, any manipulation of the separations to be

printed either through etching of printing stones, changes of exposure times when using process cameras, or

changing calibration curves in a digital system are all forms of color management since they all are intended to

change/improve the color output of the final printed piece. It is beyond the scope of this white paper to go into

the history of how color was produced and enhanced in previous pre-press systems. Rather this white paper will

define current color management concepts and offerings from Global Graphics with regards to color workflows

that require color management.

Photographic & Printing PrinciplesIn today’s graphic arts market images are still captured on film and scanned but there is a steady growth in digital

cameras as well. This in a way is putting the scanner in the camera. The result in either case is an original scene

captured in color through a lens, either via the scanner lens when scanning film or a digital camera lens captured

into a digital file format. In most cases this is a RGB color space. Some scanners can generate a CMYK file

however this will limit the re-usability in later design work and therefore will not be included in the discussion. The

captured digital file is typically viewed on a RGB monitor for editing incorporating enhancements that may include

sharpening, color correction and cropping. This would be considered the starting point in a pre-press workflow

where this original scene capture is going to be used in a future printed piece.

Color management if implemented, could already be in use in this scenario by mapping the RGB colors in the

original file into the monitor’s color space, or stated another way, the best representation of those original colors

within the color gamut limitations of the monitor. What this concept suggests is that the scene brightness or

dynamic range in the original is often larger than the RGB color space that has been used to render it and

therefore color management must be used to compress the colors in such a way as to keep the visual

This white paper details

Global Graphics' Color

Management solutions

using the Harlequin RIP.

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appearance of the original scene on the monitor as close as possible to that original scene. This form of image

representation is known as additive and is emissive since the monitor is emitting light.

Graphic arts printing makes use of CMY (K) inks which are cyan, magenta, yellow and black inks. If the CMY inks

were spectrally pure one could print all colors very accurately and black would not be necessary. Primarily due to

costs in their manufacture printing inks are not pure so a combination of CMYK inks will provide the best

opportunity to print the greatest number of colors within a press, ink and paper combinations gamut. CMYK

colors are produced by reflected light. Mixing colors together when printing a color image, the inks together

subtract wavelengths of light, thus the more ink on the paper the darker the color. This system therefore is a

subtractive color model, as opposed to the RGB additive model. In general the number of colors printable in a

CMYK print space is considerably smaller than a RGB emissive space so once again the original scene must be

further compressed. Illustration 1 below is an example of a RGB monitor space and a smaller CMYK print space

typical of magazine printing. Color management can be one way of further compressing the colors in the original

scene in such a way that insures the printed image looks visually correct and is representative of the original

scene. The quality of this process from original scene to printed image on a printing press, in today’s digital world, is

really color engineering. It requires a combination of color software specifications, industry specific standards and

tools to build the color components of a pre-press workflow, an area that Global Graphics and the Harlequin RIP

have been at the forefront of since the beginning of printing color digitally.

Company logos, artwork, and Black and White imagesOften times a design includes a company logo or artwork that has a specific color requirement for example colors

that are from a proprietary library like Pantone or a combination of CMYK colors that are known to be within

the press gamut of the printing system and must be printed in such a way as to achieve a specified color. The

Harlequin RIP includes colorimetric lookup tables for almost all of the Pantone colors in named databases and

additional color databases can be added. These databases insure that customer colors are printed accurately but also

that digital proofs can accurately print these custom colors when proofs are part of the workflow and approval process.

Illustration 1 – RGB Monitor Color Space

vs. Coated Paper Color Space

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Black & White images are often found in design layouts and with the Harlequin RIP these can be handled

differently than color work. In other words, should one have multiple black & white images within a layout, from

different sources, a black and white profile could be installed in the RIP and then applied to all black & white

images. This would insure the tonality of these black & white images are consistent throughout the publication.

Device Dependence vs. Device IndependenceBoth RGB and CMYK color spaces are known as color models that are device dependent. Thus if you view the

same RGB image on two different monitors they will look different. This is because the monitors likely have slightly

different white and black points and therefore the internal gamuts are different as well. This can be corrected using

color management. In the CMYK print space if the same CMYK values are sent to two different printers the

printed pieces would likely look different because the inks are different. The solid ink densities at the time of

printing would also likely be different, another reason the printed pieces would look different. Thus the CMYK

values in the file are device dependent. They would produce predictable color on a single device but the CMYK

file would produce different colors on a different device. In some workflows this would be okay and nothing more

would be needed but in many modern digital workflows often times the final output device is not known at the

design stage. This again can be handled with color management if engineered properly.

Color Management elementsThe elements, the color bits if you will, that comprise a color management system for the graphic arts contains at

a basic level a source/input profile, a CMM and a destination/output profile. The input profile defines the colors in

the source or input space in such a way as to align RGB or CMYK values to LAB (a uniform intermediary color

space). The processing engine is the intermediary place to process/convert the profiles, and is called a Color

Management Module (CMM). The CMM contains the Profile Connection Space (PCS) which is a conversion color

space. The destination or output profile takes the LAB values that the CMM has identified in the source image and

profile, looks them up in the table of LAB to CMYK values in the output profile, which then gives the appropriate

CMYK values to print a specific color on the printer or press sheet (via the plate and press) as needed.

The power in this solution and working model is a designer working in RGB does not have to know where their

work is going to be printed and still obtain a quality print within the gamut limitations of the output device. Obviously

a pre-press system could be optimized if the output destination is known along with the ability to produce color

accurate digital proofs but the principle is that once a color space is converted to LAB via a profile and CMM, the

destination for output can change and an acceptable print can be produced on a variety of output devices. This is

known as device independent color and used in some graphic arts workflows. The profiles mentioned can be ICC

profiles based on the ICC specification (more information can be found at www.color.org) or proprietary formats

that are capable of providing additional parameters unavailable within the ICC profile specification.

Defining Workflows - late Binding/early BindingThe term Color Management has gained in popularity when talking about software, hardware and measurement

devices used in colorimetry and likely has somewhat different definitions. Part of the challenge in succeeding at

printing in the digital age is to understand the elements that must be controlled and “engineered” to insure

predictable and color accurate prints that meets the requirements of one’s clients. Marketing people have also

recognized the inherent advantages and often tout that their products(s) in the workflow chain, be it software or

hardware is color management capable. So, if I am a designer do I turn on color management in image

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manipulation software, then my page layout application then my RIP? Isn’t this going to insure that my color

elements are color managed properly? Well, the answer depends, and the secret is understanding what it takes to

build a color managed workflow, the elements involved, and when color management would best be applied.

The Harlequin RIP is fully capable of performing all of the necessary color management because it can make use

of ICC profiles and Harlequin HQ profiles (which contain extra color information unavailable in ICC profiles), to

convert between color spaces as needed on the way to the intended output device. The Harlequin RIP CMM

would be considered late-binding as all of the color management decisions are performed at the last stage of the

workflow, that of converting the page files or PDL into a raster form, appropriate for the intended output device.

Thus a designer who receives digital images from a digital camera in a

RGB color space can place those images on a page layout and provided

the workflow is designed properly and the correct profiles are either

attached to the images or installed and made available in the RIP, all RGB

images can be handled and optimized properly at the RIP. CMYK image

data can be also color managed accurately at the RIP, again with either

properly attached profiles or profiles that are in the RIP. PDF/X files are

also color managed correctly in the Harlequin RIP as the profiles

selected for output and identified in the PDF/X format are honored.

There are options to use additional profiles to produce color accurate

proofs to a variety of output devices. Yet some other examples of the

color management capabilities of the Harlequin RIP with a properly

engineered workflow includes the ability to accurately color manage

mixed color space files where perhaps the pictorial images are in RGB

and the advertisements are in CMYK. Perhaps a last minute press change

is required. Again if the appropriate profiles have been installed an

emulation workflow can be color managed to redirect/repurpose the data for a different press condition keeping

the colors accurate. Finally, the graphic arts standards bodies continue to develop standards that define different

printing conditions for different industry segments. Global Graphics is an active participant in these trend setting

industry standard groups. The Harlequin RIP continues to be engineered to insure these standards are

implemented properly thereby insuring that the color meets a given standard and client’s expectation. Recently for

example we obtained SWOP® certification on an ink proofing device to demonstrate our capability in this area.

Building WorkflowsThe key to predictable color is the ability to configure the pre-press workflow such that files prepared for printing

when arriving at the RIP will be color managed appropriately. With the advent of the digital revolution this process

has caused a great deal of confusion. The Harlequin RIP has been developed to handle a variety of situations by

providing flexibility in setup of color managed workflows. One avenue is via a JDF front end which contains

instructions on how files are to be managed be it fonts, screening, or color management. The Harlequin RIP is JDF

compliant and remains current with the JDF specifications as it evolves. PDF/X file formats developed to improve

file submission accuracy to printers can have a profile and specific color requirements. The Harlequin RIP

recognizes PDF/X file formats, provides pertinent information as to file contents and RIP configuration insuring that

color management is honored and handled correctly.

For many types of printing a digital color proof is required to insure that the designer, customer and printer are all

working towards the same end point. This requires considerable engineering to insure that the digital proofs are

"Color management requires

a combination of color

software specifications,

industry specific standards

and tools to build the color

components of a

pre-press workflow".

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representative of future printing. A source/input profile must be created for the press and a destination/output

profile must be created for the proofing device. For each combination of paper, ink, screening and resolution, the

printing characteristics of the printing device changes and therefore the color will change as well. Once the color

characterizations are built into profiles for each printing condition they can be installed into the Harlequin RIP and

used in a variety of Harlequin ColorPro™ setups to meet customer requirements. Illustration 2 below highlights

some workflow options using profiles and a variety of input color spaces.

Harlequin setGoldPro™

Part of the success of developing color managed workflows is the building of profiles that capture the color

space/gamut of a device accurately and then have these profiles available to the RIP. Harlequin SetGoldPro uses

patented gray balance techniques along with sophisticated algorithms to build profiles that are optimized for the

Harlequin RIP. In fact Harlequin SetGoldPro provides the ability to work with a specific RIP so that when the data

has been imported and a profile generated, the resultant profile is placed in the appropriate location within RIP and

also made available in Harlequin ColorPro within the RIP for immediate use. This insures both installation and color

accuracy as the profiles have been optimized for the Harlequin RIP and press or proof condition being characterized.

Harlequin ColorProColorPro is the GUI interface to the Harlequin RIP kernel where all color managed workflow decisions are setup.

This window is feature rich and has evolved to be useable by novice users as well as for operators needing to

design complex color managed workflows. It should be mentioned again that setting up a color managed

workflow at the RIP stage is known as late-binding and offers very powerful control over the color management

of jobs when the source is known. It is also very controllable even when jobs files from unknown sources (a new

customer for example) need to be accurately output in preparation for printing or plate making. In addition to the

feature set found in the Harlequin ColorPro window many additional features can be initiated via PostScript®

Illustration 2 – Color Spaces and Color Conversion Routes

the smarter alternative, Harlequin, the Harlequin logo, Eclipse Release, Genesis Release, SetGold and ColorPro are trademarks of Global Graphics Software Limited which may be registered in certain jurisdictions. GlobalGraphics is a trademarkof Global Graphics S.A. which may be registered in certain jurisdictions. Adobe and PostScript are a trademarks of Adobe Systems, Inc., which may be registered in certain jurisdictions. All otherbrand and product names are trademarks or registered trademarks of their respective owners. All specifications subject to change without notice. Global Graphics makes no warranty and accepts no liability for any lossor damage arising from the useof information or particulars in this document. Copyright © 2006 Global Graphics Software Limited. All rights reserved.

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commands to even further control how page elements within a file are color managed. The Harlequin ColorPro

window was designed to allow for most operations but not so complicated as to have limited usability. For more

information please refer to the Harlequin ColorPro User’s Guide for the Harlequin RIP.

ConclusionColor Management is a combination of color engineering and correct workflow setup. This includes the necessary

transforms to move between different color spaces, applications to build those transforms into profiles, and a

decision on where the color transforms take place. If one needs color accurate proofs the obvious location is at

the RIP. If one is receiving job files that are not tagged for specific printing application these files will need

conversion. Again the Harlequin RIP is ideally suited for this purpose as all of the color bits can be loaded and

configured to correct color issues within files (wrong or no profile attached to the submitted images). If one needs

to change the printing condition the job files will need conversion. This example would be through emulation as

seen in illustration 2 and is a way one can repurpose data or optimize data prepared for one press that at the last

minute needs to be printed on a different press.

Using the Harlequin RIP and color tools optimized for the RIP insures that any workflow challenges can be

accurately configured at the RIP prior to printing, plating or proofing. Keeping these color decisions available to the

latest possible stage helps limit mistakes and provides a greatest flexibility to optimizing jobs that may have been

setup for one print condition but now need to run in a different set of conditions.

www.globalgraphics.com

September 2007

Global Graphics Software Inc.

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Global Graphics Software Ltd.

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Global Graphics KK

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one TECHNOLOGY TO SUPPORT one SCALABLE ARCHITECTURE one SOURCE

ColorPro GUI