廣告燈箱彩白彩UV輸出色彩管理與色彩品質研究

A Color Management Applicationand Color Quality EvaluationResearch of the 4C-W-4C UV InkjetPrinted Outdoor Advertising LightBox

戶外廣告燈箱是不易控制色彩品質的，原因是「戶外」照明的不可控制性，「燈箱」同時是反射式與透射式的顏色載體，再則燈箱內部的光源種類變數，一般燈箱以「UV 彩白彩」的三層噴墨方式輸出，尤其是夜間透射式所呈現的顏色是經由彩色、白墨和彩色三層的結果，如何控制好色彩的表現是極為重要的課題。本研究目的在分析UV 噴墨輸出的ICC Profile 對於廣告燈箱色彩的準確度、可正確複製色彩能力與色域大小的相關程度，並以廣告設計業者最為熟悉的PANTONE Formula Guide 4.0 Coated色票指南為評估工具，評估不同階調白墨與4C 彩色組合輸出的ICC Profile，對應至PANTONE 色票結果。研究採用準實驗法（Quasi Experiment），自變項為不同階調白墨與彩色組合UV 輸出的ICC Profile，依變項則是彩白彩廣告燈箱色彩表現的準確程度、輸出控制能力以及色域空間大小。結果顯示濃度較淡的2 個白墨階調的透射式圖像（即ICCT25 與ICCT50），圖像的反差效果不足且色彩過於飽和鮮豔，而在75% 白墨的透射式圖像（即ICCT75）開始，影像的階調、反差、飽和度、膚色以及中性色表現皆良好，而反射式的色域空間雖較小，卻己接近印刷ISO 15339 的CRPC6 標準，在透射式LED 燈片下的視覺觀察發現，在75% 白墨與透射式彩色的ICC profile（ICCT75）擁有較接近標準圖像的色彩階調與飽和度。在75% 白墨與透射式彩色ICCprofile（ICCT75）開始得到較佳的色彩品質，所能複製的Pantone Formula Guide 4.0Coated 色票的數量也達到最高數值，由此可知，底層「彩白」的ICCT75 色彩描述檔加上表層的「彩」的ICCR 是綜合「白墨遮蔽」與「底層彩色透射」的最佳化組合。在除去ICCT25 與ICCT50 的數據後進行分析，結果顯示不同階調白墨與彩色組合UV 輸出的ICC profile 對於廣告燈箱色彩準確性有顯著影響；不同階調白墨與彩色組合UV 輸出的ICC Profile 對於廣告燈箱色彩輸出能力「有顯著」影響；以及不同階調白墨與彩色組合UV 輸出的ICC Profile 對於廣告燈箱色域空間大小「有顯著」影響。總而言之，本研究證明廣告業在執行彩白彩戶外廣告燈箱輸出時的色彩管理可以採用先落實表層反射稿ICC profile 的建立，底層透射式輸出搭配飽和度高的白墨與彩色ICCprofile 的組合，由二個色彩描述檔共同維持反射式與透射式的色彩品質。

The color quality of an outdoor advertising lightbox is difficult to handle, due to the outdoor illuminant isunpredictable and the advertising light box itself is both areflective and transmissive types of color device. Moreove,rthe light source of any advertising light box is diverse.Especially, during the night time, the light box generates colorsthrough three layers of media, 4-Color Process, white, and4 color print layers. To control the color quality of light boxbecomes an important issue. The purpose of this research wasto analyze the relationship of various UV inkjet printer ICCprofiles with color accuracy, color controllability, and colorgamut. The PANTONE Formula Guide 4.0 Coated Guidewas adopted as a color evaluation tools to analyze those UVinkjet ICC profiles. The research defined that the numbers ofcolor swatches of the PANTONE Formula Guide 4.0 CoatedGuide by an ICC profile under the condition of ΔE00 ≦ 1is related to the ‘Color Accuracy’, the numbers of colorswatches of the PANTONE Formula Guide 4.0 Coated Guideby an ICC profile under the condition of ΔE00 ≦ 2 is relatedto the ‘Color Controllability’, and the numbers of colorswatches of the PANTONE Formula Guide 4.0 Coated Guideby an ICC profile under the condition of ΔE00 ≦ 3 is relatedto the ‘Color Gamut’. A quasi-experiment was used inthe research, and the independent variables were differentgradient of UV white-ink plus color combination output ICCprofiles, and the dependent variables were the color accuracy,color controllability, and color gamut. The results showed thattwo ICC profiles (ICCT25 and ICC T50) among them, generatedtwo unsatisfied color quality (low control saturation andcontrast). The ICCT__ demonstrated an excellent performancein the aspects of smooth gradient, sufficient color control andsaturation, and neutral gray balance. A lthough, the reflectiveICCR created a smaller color gamut, but achieved the standardof CRPC6, ISO 15339. Meanwhile, from the ICCT75 to ICCT200demonstrated a significant negative correlation to the coloraccuracy, color controllability, and color gamut. Furthermore,the ICCT75 reached the peak of the numbers of PANTONEFormula Guide 4.0 Coated Guide swatches, which meansthe ICCT75 was the most appropriated output ICC profilescombined with the reflective ICCR and demonstrated a finecolor quality, which was color accuracy, color controllability,and color gamut.