Optimum Flexible Hybrid Screening for Offset Lithography


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Dr. Yung-Cheng Hsieh and Dr. Yu-Ju Wu


Digital, Non-Member: 
Photo, Member: 
Photo, Non-Member: 


This study investigated the use of AM/FM (Amplitude Modulation/Frequency Modulation) hybrid screening in  conjunction with computer to plate (CTP) technology in order to obtain an optimum hybrid screening combination for the offset lithographic printing process. The study designed nine different hybrid (FM-AM-FM; highlight-midtone-shadow) screening combinations in accordance with one of the few flexible (adjustable) hybrid screening technologies. Hybrid screening and CTP technologies were used in offset lithography to print a digital test form on matte-finish paper. Differences in print attributes between matte-finish paper printed via the nine hybrid screening combinations were measured by a spectrodensitometer, and statistical analyses were used to identify a combination with an optimum FM-AM-FM tone percentage. It was that the most optimum FM-AM-FM screen combination is 10-70-20 (i.e., 0%~10% is FM; 11%~80% is AM; 81%~100% is FM). The hybrid combination of 10-60-30 is identified as the second best combination. It is hoped that the results of this study can help offset lithographic printers to better understand the characteristics of various screening techniques, allowing them to improve printing quality and achieve the highest customer satisfaction. The best hybrid screening combination of FM-AM-FM (highlight-midtone-shadow) found in this study is provided to printers as a reference enabling them to improve production effectiveness and quality, while reducing printing costs and waste, enabling the quality of offset lithography in Taiwan to progress.

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