平版八色廣色域印刷之適性初探

Abstract

平版印刷產品與電腦上面看到的色彩，由於色光與色料媒材的演色方式的差異，因此，會有一定的差距。將大眾印象中的顏色以平版印刷的方式印刷出來，是印刷工藝所追求的目標，但是將大眾印象中的顏色印刷出來，並不是很容易的工作，需要有經驗的印刷工作人員、技術、工具以及設備的支援。電腦上色彩的標準，以Adobe RGB色域或是sRGB為比較基準，平版印刷技術可以呈現四色外加RGB中間色之下，可呈現與電腦畫面接近的產品。為了打破原來傳統四色所限定的色域框架，在2015年由idealliance組織推動，東明油墨進行開發的－XCMYK擴色域油墨，是一套全新四色印刷的擴色域印刷技術。本文油墨色彩以八色(XC、XM、XY、K+O、G、V、RR)來因應的廣色域印刷以因應電子傳媒挑戰。本研究針對八色廣色域平版印刷技術所印刷的平版印刷品，提出測驗方法，包含設計實驗流程，準備不同種類印刷品，並呈現實驗結果，驗證八色廣色域平版印刷技術所能達到的涵蓋率以及降低色差的比例(△E)，並生產八色廣色域的演色表做為複製依據。本研究實驗內容以不同風格的平版印刷產品，就電腦螢幕所顯現出的畫面，與八色廣色域平版印刷列印出來的實體產品，以分光光度計來進行測量，比較印刷結果與電子檔圖片的差異。研究結果，提供設計師可參考比對，提高設計更多顏色的選擇性，並且提高平版印刷樣本確認效率。There is a difference between the color of offset lithographic products and the color seen on the computer due to the difference in the way the color light and the color material evolve. It is the goal of the printing process to print the colors that the public perceives by offset printing, but it is not an easy task to print the colors that the public perceives. It requires experienced printing staff, skills, tools and equipment support. The more coverage the offset printing technology can present, the better the product will look like the computer screen. The computer color standard is based on Adobe RGB or sRGB, and lithography technology can present four colors plus RGB intermediate colors, which can present products close to the computer screen. In order to break the traditional four-color framework, the XCMYK Extended Gamut Ink, which was developed in 2015 by the IDEALliance organization, is a new set of extended gamut printing technology with a wide color gamut from eight colors (XC, XM, XY, K+O, G, V, RR) which can significantly reduce the difference in color performance between printing gamut and inkjet printing. This study proposes a test method for eight-color wide gamut offset printing, which includes designing the experimental procedure, preparing different types of prints, and presenting the experimental results to verify the coverage and the percentage of color difference reduction (△E). Also, the results will be produced in a color table for an eight-color wide gamut. In this study, the difference between the computer screen image and the physical product printed out by eight-color gamut offset printing was measured by spectrophotometer using different styles of offset printing products, and the difference between the printed result and the electronic file image was compared. The results of the study provide designers with a reference for comparison, improve color selection, and enhance the efficiency of sample verification.