In a late binding workflow, data is commonly prepared in an output-referred state based on a reference intermediate RGB
colour encoding. Such encodings may have a larger gamut than the target printing condition, and so there is some
ambiguity over how to preview the data before it has been converted to the target printing condition.
Here we propose an additional intermediate encoding, referred to as a 'virtual printer' which bridges the gap between
three-component reference RGB or PCS encodings, and reference CMYK printing conditions.
The virtual printer has a large colour gamut which represents a superset of most available print gamuts. It is defined here
in terms of the reflectance and colorimetric coordinates of the virtual colorants, and associated colour mixing model.
When used in a colour reproduction workflow, documents can be initially rendered to the printer-like gamut of the
virtual printer, and channel preferences (such as black generation) can be defined. Re-rendering to a reference printing
condition and associated colour gamut is deferred, thus supporting re-purposing of the document.
I am sure that everyone would agree that the standards that define colorimetric measurements (ISO 13655) and viewing conditions (ISO 3664)for graphic arts and photography, and ICC profile building (ISO 15076-1) must all be consistent with each other. More importantly we would all agree that together they must be consistent with current industry practice and be technically sound. However, as we begin the process of revising the color measurement and viewing standards we find that that is easier said than done. In each of these areas there seem to be a series of inconsistencies between what we do and what we say we should do. The real riddle is how do we reconcile them with each other, with industry practice, and also keep them technically sound. This paper looks at some of the issues, identifies the conflicts, and identifies some of the potential compromise positions. It also describes the steps that are being taken to develop revised versions of the key standards involved.
The processes and procedures used to develop both ANSI and International Standards can appear daunting and unwieldy to newcomers to the world of standards. However, once understood, these processes and procedures can become valuable resources in the development of the co-operative agreements that we call standards. This is particularly true in the area of image quality for electronic system specification, measurement and design - the subject of this conference. This is a subject area where the interests of several different application technologies converge as do the responsibilities of several different standards communities. A brief overview of the structure of ANSI, ISO, and IEC will be given, along with a roadmap of the key groups (and their inter-relationships) applicable to image quality. A summary will be given of the key image-quality standardization activities currently underway in these groups. This overview will draw on practical examples of the issues, challenges and solutions experienced by the author in many years of involvement in both ANSI and ISO standards activities, particularly in ISO/TC130 (Graphic technology) and ISO/TC42 (Photography), which are two of the key committees that have a vested interest in image quality and color reproduction in digital systems.
In the modern world of image technology, standards are developed by many different groups, each with specific applications in mind. While some of these groups are part of the accredited standards community - ISO, IEC, CIE, ITU, etc. others are industrial organizations, or consortia.
The use of colorimetric data is increasing exponentially in all area of image technology. This is being driven by both the availability of moderately priced instrumentation that makes acquisition of this type of data economically feasible, and by the increase in computing power that allows images to be processed and transformed using colorimetric tools. Too often the people using colorimetric data, to create color management profiles or other transforms, have little experience in either making spectral reflectance measurements or in computing the colorimetric parameters that are based on these measurements. In addition, although many people working in either graphic arts or photography have an intuitive understanding of process variation expressed in terms of density, few have extrapolated this understanding into colorimetry. This paper will discuss typical levels of uncertainty in measurement of spectral reflectance factor and the associated uncertainty in CIELAB values computed from these data. It will also provide some typical relationships between status density and colorimetry. Included are some generalized relationships that can be used as intuitive guides to assist users in evaluating the significance of colorimetric differences reported in terms of CIE delta-E.
With file formats for graphics arts data exchange in place and being rapidly implemented, increased emphasis is being placed on standards that help define the meaning of the image data being exchanged. Standards relating to color data definition, therefore, play a dominant role in both the US and international graphic arts standards activities. There is a clear understanding of the key role that printing process definition standards, and metrology standards, play in helping define stable process conditions to which color characterization data can be related. In addition, it has been generally accepted that, for data exchange and colorimetric profile definition, only a limited number of printing conditions needs to be defined. The color management process can be separated such that printing aims and individual printing press profiles can be handled as separate issues and not confounded together. The current status of work in support of this new perspective will be summarized. The existing portfolio of standards will also be reviewed, including those standards that have been published to define color measurement and computation requirements, scanner input characterization targets, four-color output characterization, graphic arts applications for both transmission and reflection densitometry. An update will also be provided on the continuing work on standards relating to ink testing, reference ink color specifications, and printing process definition.
KEYWORDS: Printing, Standards development, Graphic arts, Color management, CMYK color model, Process control, Data analysis, Visualization, Image processing, Solids
Color management in the graphic arts industry requires control of the printing conditions and knowledge of the intended output color characteristics. As the industry continues its accelerated move toward complete digital work flow, the need for reference printing characterization data is a requirement to enable color management of digital data. The Committee for Graphic Arts Technologies Standards, CGATS, has been supporting the industry by developing a protocol including measurement, data analysis, and data reporting format that results in characterization data for specific reference printing processes. This paper provides a summary of the protocol that has evolved from the continued standards development within the CGATS SC4 Process Control Subcommittee.
Graphic arts related color standards activities are being pursued by ISO Technical Committee 130 (TC130) Graphic technology, and ANSI Committee CGATS (Committee for Graphic Arts Technologies Standards). The content and application of the existing graphic arts color related standards are summarized. These are focused primarily on issues of metrology, color characterization targets, and reference images. The ongoing work has grown out of the need to understand the applicability of color management in the graphic arts work flow and the associated meaning of CMYK data. This has resulted in a growing understanding that, through definition and characterization of the output printing process, CMYK data can be effectively 'device independent,' although possibly not gamut independent. The ongoing work relating to the definition and characterization of various output printing process is also summarized.
The ANSI IT8.7/1-1993 standard defines the requirements for color film targets, intended for the characterization of color input scanners for graphic arts applications. These targets are created by the film manufacturer, based on their understanding of the capabilities of the specific photographic film product used, and in accordance with the guidelines of the standard. The manufacturer of the target is required to furnish colorimetric data describing the targets, either for individual targets or as batch average data. The standard makes provision for the reporting of the colorimetric parameters based on either integrating sphere- referenced measurements or opal-glass diffuser-referenced measurements. The integrating sphere is the more conventional geometry for colorimetric data while opal-glass is the specified geometry for densitometric data. Many new spectral measurement instruments, that are intended to provide both density and colorimetric data, use an opal- glass diffuser.
Standards relating to color data definition continue to be a dominant theme in both the US and international graphic arts standards activity. There is a growing understanding of the role that metrology and printing process definition play in helping define stable conditions to which color characterization data can be related. Standards have been published to define color measurement and computation requirements, scanner input characterization targets, four- color output characterization, and graphic arts applications for both transmission and reflection densitometry. Work continues on standards relating to ink testing, reference ink color specifications, and printing process definition. In addition, efforts are underway to document, in ANSI and ISO Technical Reports, colorimetric characterization data for those printing processes having broad-based usage. These include various applications of offset, gravure, and flexographic printing processes. Such data is key to the success of color profiles developed in accordance with the specifications being developed by the International Color Consortium. The published graphic arts imaging and color- related standards and technical reports are summarized and the current status of the work in progress is reviewed. In addition, the interaction of the formal standards programs and other industry-driven color activities is discussed.
Color definition and data exchange continue to be dominant themes in both the US and international graphic arts standards activity. However, there is a growing understanding of the role that metrology and printing process definition play in helping define stable process conditions to which color characterization data can be related. Standards have already been published that define the requirements for color measurement and computation, scanner input characterization targets, four-color output characterization data sets, and graphic arts applications of densitometry. Work continues on standards relating to ink testing and ink color specifications. The numerical specifications of SWOP proof printing have been captured in ANSI standard CGATS.6-1995. Work has been completed, and Technical Report ANSI CGATS TR 001-1995 has been published, that relates the colorimetry of the printed sheet to the CMYK input for press proofing meeting SWOP and CGATS.6 specifications. Work is ongoing to provide similar data for other printing processes. Such color characterization data is key to the development of color profiles for standard printing conditions. Specifications for color profiles, to allow color definitions to be moved between color management systems, are being developed by the International Color Consortium. The existing graphic arts data exchange, process control, and color related standards are summarized and the current status of work in progress is reviewed. In addition, the interaction of the formal standards programs and other industry-driven specification activity is discussed.
The digital exchange of graphic arts material - particularly advertising material for publications- in an open standardized environment represents the ultimate challenge for electronic data exchange. To meet the needs of publication advertising, the graphic arts industry must be able to transmit advertisements in an open environment where there are many senders and many receivers of the material. The material being transmitted consists of combinations of pictorial material, text, and line art with these elements superimposed on top of each other and/or interrelated in complex ways.
The business relationships established by the traditional workflow environment, the combination of aesthetic and technical requirements, and the large base of existing hardware and software play a major role in limiting the options available. Existing first- and second-generation standards are focused on the CEPS environment, which operates on and stores data as raster files. The revolution in personal computer hardware and software, and the acceptance of these tools by the graphic arts community, dictates that standards must also be created and implemented for this world of vector/raster-based systems.
The requirements for digital distribution of advertising material for publications, the existing graphic arts standards base, and the anticipation of future standards developments in response to these needs are explored.
Color continues to be an important issue in both the US and international graphic arts standards activity. Standards have been published defining color measurement and computation requirements, scanner input characterization targets, four color output characterization and reflection densitometric data. Work continues on standards relating to ink testing, reference ink color specifications, and printing characterization. Work has been completed, and is being published in an ANSI Technical Report, that relates the measured colorimetric data for printed color to the CMYK input for press proofing meeting SWOP specifications. Implementation of the color standards developed by IT8. CGATS, and ISO/TC130 is being promoted by the Open Systems Color Association (OSCA). Key among the OSCA activities is the development of measurement protocols and a registry of color output characterization data. These color standards are also finding applicability in the work of the International Color Consortium which is developing the interfaces to allow color profile data to be exchanged between color management systems. This presentation will summarize the published graphic arts color-related standards and review the current status of the work in progress.
ANSI/IT8, ANSI/CGATS and ISO/TC130 are actively working on standards that help define color for graphic arts applications. This paper describes the standards already in place as well as a summary of the current status of the work underway and/or planned. This includes standards that define colorimetric measurement, targets and data sets for calibration of input devices such as scanners as well as color hard copy output (including printing) devices and standards for the definition of printing processes. The work to develop characterization data sets for use by color management systems and common data formats for the exchange and presentation of this data are also discussed. Key additional areas include the definition of default three-component color data spaces, their practical encoding in 8- and 16-bit formats, and procedures for definition of ink colors in a printing independent manner.
The color definition activities of Subcommittee 4 of ANSI Standards Committee IT8 (Digital Data Exchange Standards) are described. This subcommittee is charged with the responsibility of developing color calibration tools, color definitions, reference targets, and data sets necessary to facilitate color data exchange within the graphic arts electronic prepress application area. Two standards (IT8.7/1 and IT8.7/2) have been completed which define targets for input scanner calibration with transparency and reflection photographic products. A third standard (IT8.7/3) has been completed which provides a reference data set for CMYK to printed-color characterization. Work is still continuing on the development of a scanner calibration target for use with negative films and on the development of default definitions for three-component color data exchange.
This paper discusses the status of graphic arts standards activities within the United States and the international community relating to color definition. A brief description of the organization of standards groups that are involved in graphic arts activity is given. The principal focus is on the activities of Working Group (WG) 11, Color, of ANSI Standards Committee IT8 (Digital Data Exchange Standards). Additional work being carried out in ANSI Committee CGATS (Committee for Graphic Arts Technologies Standards) is also discussed.
When I was asked to prepare this paper, my immediate response was that the topic was overwhelming. However, the more I thought about the issues the more I realized that because we understand so little about color and electronic imaging, I could get away with almost anything. I won’t take that much freedom.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.