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FLEXO Magazine : May 2009
TECHNOLOGIES & TECHNIQUES TABLE 2. CIE LABCH is not enough information to ensure visual correlation. Delta EAB Red Green Yellow D65/10˚ 9.52 10.3 4.86 D50/10˚ 4.85 5.86 7.93 * Reference color was measured with Instrument 1, D50/2˚ ** Instruments 2, 3 and 4 used D50/2˚ GETTING STARTED TODAY As more research and development is completed to streamline and integrate spot color management, there are steps to take today to improve your existing spot color workfl ows. Let’s begin to remove the weakest link within the chain of spot color management. That starts with the initial color standard. The pressroom can only be accountable for the amount of information that is provided from the broker or customer. There are tools available today to begin to push proper color defi nitions up the supply chain to the customer and designer level. When developing spot color standards, consider including color standards for some steps within the tonal range, and overprint information. There are testing (or laboratory type) systems in place at Clemson and at many other facilities, that utilize fl exographic plates, mounting materials, anilox rollers, and doctor blades to reproduce test-prints at realistic production speeds on production substrates. Moving forward, the research outlined above allows the color standard to be printed on a standardized substrate, not production substrate, but then use production substrate profi les to calculate color values. Once the standard has been approved, the next practical step to improve communication is to accurately defi ne the color measurement. Make sure to capture spectral data as your root color value, and decide on the illuminant and observer functions to be used for distribution. When communicating CIE LABCH of your color standard, include the illuminant, observer, and instrument used in determining these values, as it will drastically infl uence the visual color (Table 2). If the color is going to be used in screen-work, which is most often the case, it is very important to include a reference color value for the screen-work as well, for instance 50 percent. There are several ways to tackle this problem: with dot area, density, CIE LABCH, or spectral. The pressroom and prepress operators most often times are already required to measure the color of the solid Instrument 2 0.79 0.88 1.61 Instrument 3 3.39 2.67 2.59 Instrument 4 2.09 2.56 1.22 in CIE LABCH or spectral to calculate a ∆E. The easiest way to incorporate control of the screen value is to work within the existing system for solid color control, which is to publish a standard color value for the 50 percent (or custom) tone, and have the supply chain use this color reference as the standard against which to measure ∆E. This information is used for troubleshooting color reproduction and to ensure the proof is produced to a known customer expectation. How does this information help the supply chain? • Quicker makeready and less waste in the pressroom. • Right-the-fi rst-time/quicker time to market for new graphics and colors. • Accurate contract proofi ng eliminating customer confusion. • Provides a metric for process quality control/repeatability for packaging graphics. In prepress, try to include accurate spot colors, and spot color screen-work, in-line with CMYK contract color proofi ng. Once accurate color references are identifi ed, it is just a matter of incorporating those specifi cations within the proofi ng RIP and objective quality control system. In the pressroom, begin to train operators, management, and quality control how to use color measurement and Delta E reporting to assist makeready and production consistency. Digitally capture and store this information to identify improvement areas, and track and trend pressroom color management capabilities. Emphasize measurement protocol, including instrument settings, calibration methods, and measurement backing material to ensure accuracy and visual correlation to results. SUMMARY This article reviewed current limitations in the marketplace for spot color management, tools and workfl ows that can enable better prediction for color control, and research currently underway to improve total color accuracy throughout the supply chain. Also mentioned were several things companies are already doing today, or could be doing today, to begin to improve spot color communication and spot color control. Clemson provides an open forum for you to participate, so if you have any questions or comments please don’t hesitate to stay in touch and get involved. ■ ABOUT THE AUTHOR: Relationship of substrate chroma to change in ink chroma. 34 FLEXO MAY 2009 Jay Sperry is a research associate and lecturer representing the Department of Graphic Communications in the Sonoco Institute of Packaging Design and Graphics at Clemson University. Sperry holds a Bachelors degree in Graphic Arts from Appalachian State and a Masters in Graphic Communications from Clemson. His research topics include printed electronics, color reproduction systems, the consumer experience, and advanced techniques in fl exography. www. f le xography. org