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GATF Study Questions Value of Measuring Ink-Trapping, Compares Systems

Press release from the issuing company

Pittsburgh, Pa., February 19, 2002 — Should printers measure ink trapping as a part of their process control strategy? Trapping is not mentioned in current industry-wide specifications, yet virtually every color control bar sold today contains the necessary patches in the right proximity for making ink trapping measurements. Furthermore, ink trapping software is included in all densitometers and print attribute systems on the market today. This contradiction led the Graphic Arts Technical Foundation (GATF) to conduct an original research study on whether ink trapping is a useful indicator of the color properties of overprints. "Yes, changes in trap values do correlate with perceptual changes of overprint colors," says Dr. Anthony P. Stanton who conducted the study, a senior lecturer and director of Graphic Media Management at Carnegie Mellon University. To then help printers determine which trap calculation method is the most sensitive to colorimeteric changes, he has recently published Ink Trapping and Colorimetric Variation. This newly published report documents his findings on why trapping is important and compares four equations (the Preucil, Brunner, Childers, and Ritz formulas) for calculating ink trapping, with respect to their correlations with color differences measured by the CIE94 equation. A single color difference formula (CIE94) was selected after comparative calculations were made with three color difference formulas. Stanton also reviews the history of ink trapping, and five different equations that have been proposed over the past 45 years are presented. His study includes a brief review of different approaches to measuring color differences. A former director of the GATF Process Controls Division, Stanton has conducted research studies related to print attributes and process measurements, including several that have been published in TAGA Proceedings, GATFWorld magazine, and two earlier Research and Technology Reports. Ink Trapping and Colorimetric Variation is the latest study in a series of Research and Technology Reports (RTR) published by the Foundation. As an independent, third-party organization, GATF reports are objective and original research studies designed to help printers evaluate technologies on their own by guiding consumers to ask the right questions. Methodology is described in all reports. Heavily illustrated with charts and graphics, Ink Trapping and Colorimetric Variation (ISBN 0-88362-377-3) is a 48-page booklet available for $129 ($59 for GATF/PIA members), not including shipping. Orders may be placed by contacting GATF by phone at 800/662-3916 (U.S. and Canada) or 412/741-5733 (all other countries); fax at 412/741-0609; or online from the GAIN Bookstore. Mail orders to GATF Products, P.O. Box 1020, Sewickley, PA 15143-1020. Indicate Order No. 1625.