Jul 7, 2004
By Bruce L. Myers, Ph.D.
As every successful high volume printer knows, one of the key foundations for a comprehensive quality control program is the ability to accurately measure variables. The ability to assign a number to a variable, known as quantification, is fundamental to maintaining quality and consistency, improving productivity, and reducing costs. As stated succinctly by Dr. H. James Harrington, noted author and CEO of the Harrington Institute: "If you cannot measure it, you cannot control it. If you cannot control it, you cannot manage it. If you cannot manage it, you cannot improve it. It is as simple as that."
Recognizing the importance of quantification to improving key business metrics, it is curious to acknowledge that many printers have not been aggressive in the pursuit of measurement and what the subsequent data collection can offer to improve their bottom line. This is especially true of the quantification of color variables: while densitometry is widely used in many printing plants, adoption of more advanced color management techniques for incoming materials inspection as well as process control of both spot and process color reproduction is far from universal among printing organizations.
Perhaps the lack of more widespread adoption of advanced color measurement and management techniques is the result of the diligence required when one endeavors to assign a number to what is, essentially, a unique sensation to an individual observer. Unlike the more universally understood quantification metrics designed to measure length, temperature, volume and time, just to name a few, the sensation of color is a much more unique experience. It is for this reason that color measurement and management does not lend itself to quantification as simply as length, for example. A more comprehensive understanding of the technologies involved is therefore required to make the most out of a color management effort. Recent surveys of print buyers indicate that dissatisfaction with a printer frequently results from the inability of that printer to manufacture press sheets that match approved proofs, as well as that printer' ability to maintain color consistently throughout the press run. The recognition these conditions alone should be evidence enough to entice a printer concerned about customer satisfaction to take a look at current color measurement and management technologies.
The good news is that recent technological innovations have made color measurement technologies more assessable as costs have come down on both the software and instrumentation required. In general, color management software has become not only less costly but easier to use, and automated color measurement technologies have made advanced color measurement technologies also easier to use than their more manual predecessors. Widely supported standards have also helped to make color management more ubiquitous in the marketplace, as has support from the major prepress application software vendors.
Perhaps the most recognized standard when talking about color management are those developed by the International Color Consortium, or ICC. Founded in 1993, the ICC created an open color management system architecture that resulted in a profile specification that can be used to translate color among the various devices used in the printing workflow. The ICC profile® format has become the de-facto standard for comparing the ranges of colors, known as gamuts, among output devices, as well as monitors and image capture devices such as scanners and digital cameras. It is helpful to think of an ICC profile as a quantification of the gamut that a particular device can capture or produce. If the goal is more faithful color reproduction throughout the printing workflow, utilizing ICC profiles can go a long way towards accomplishing that goal.[BLM1]
To build an ICC profile, two components are necessary. The first is a software that enables the user to build the profile, and the second is a measuring device that is capable of capturing colorimetric data. The way the softwares typically work is a series of color patches are output, and then these are read back into the software using a device capable of capturing colorimetric data. Colorimetric data is the metric utilized to measure color: as previously stated one of the principal challenges in an effort to quantify color is that each individual experiences color differently. In an attempt to quantify color for commercial purposes, the CIE (Commission Internationale de l'Eclairage, or International Commission on Illumination) tested human subjects to develop a "standard observer." The CIE standard observer provides the foundation for modern colorimetry. Colorimetric data can be obtained through measurements taken with a spectrophotometer or a colorimeter.
ICC profiling software is available from several vendors for various applications. Key considerations when evaluating these software products include the ease of use and support offered by the vendor, as well as the particular functionality needed in terms of output device support, editing and workflow tools. Vendors typically offer packages to meet the needs of several segments of the marketplace, including designers, photographers, and all phases of digital prepress all the way up to the printing press. Delineation among profiling software products is often relative to the type of output device; for example, if a digital proofer is driven by a raster image process or not, or the type of process printing used, be it traditional CMYK or more advanced high fidelity printing methods.
Measurement devices necessary for ICC profiling include scanners and digital cameras for the input side, and colorimeters and spectrophotometer for building profiles of monitors and output devices. For profiling and input device, the scanner or the digital camera serves as its own colorimetric input device: targets consisting of several known colorimetric values are captured by the device and the software compares the way the image capture device "saw" each patch versus the known value, it is from this information that the ICC profile is built.[BLM2] For a monitor, the software "samples" several color patches on the screen which are captured by a spectrophotometer or colorimeter, and again measured values are compared to referenced values to build the profile. [BLM3]Similarly, for an output device several patches, frequently over 900, are output and then measured with a spectrophotometer or colorimeter to build the profile. It is in this case that advancements in the speed and automation of measurement devices are appreciated by users of these technologies.[BLM4]
When discussing color management, many people assume this term is limited to ICC-profile based color management. While ICC profiles encompass an important part of color management, a comprehensive color management effort needs to go beyond profile building and gamut definition.
For example, colorimetric information can be used for controlling spot colors and incoming materials inspection. Further, information obtained from a spectrophotometer can be utilized to monitor specialized indices such as paper brightness and whiteness. It is also important to recognize that color management is best implemented in shops where comprehensive process control is in place; a profile is only as good as the consistency of the device at the time it was built.[BLM5]
Utilizing the established work of the standards committees that serve the printing industry and taking advantage of the technological advancements that reduce the cost of entry into more comprehensive color management, today's high volume printer has never been in a better place to initiate a comprehensive color management effort. The fruits of these efforts promise to be happier customers, reduced rework, and improved productivity.
Dr. Bruce L. Myers is the Global Sales Training Manager for X-Rite, Incorporated. He also teaches color reproduction and quality control at New York University.