1. Definition

高保真印刷是相對于四色印刷而言的，通過在C、M、Y、K四色印刷的基礎上增加紅、綠、藍、橘黃等顏色油墨的方法來改善印刷顏色的再現性、真實性。

Compared with four-color printing, high fidelity printing improves the reproducibility and authenticity of printing colors by adding red, green, blue, orange and other color inks on the basis of C, m, y, K four-color printing.

高清晰度網點是指高于250lpi的調幅網點，即100%網點直徑小于125μm的調幅網點，以及等效直徑20μm以下的調頻網點。以提高印刷品清晰度為目標，采用高清晰網點進行的印刷稱為高清晰度印刷。高清晰度印刷技術可有效縮小網點的間距，提高印刷品的清晰度和層次表現能力。

High definition dot refers to the AM dot higher than 250 LPI, that is, 100% dot diameter is less than 125 μ M, and the equivalent diameter of 20 μ The frequency modulation dot below M. In order to improve the clarity of printed matter, printing with high-definition dot is called high-definition printing. High definition printing technology can effectively reduce the spacing of dots and improve the clarity and hierarchical performance of printed matter.

2.色域

2. Color gamut

高保真印刷技術的主要特征包括三個方面：，除黑墨外，C、M、Y及另外增加的彩色油墨均參與彩色分色和中性灰平衡;第二，印刷顏色階調變化比四色印刷更接近真實光譜色的變化效果，印刷品的層次感、立體感強;第三，印刷色域增加。上海印刷廠在四色印刷中，由于油墨材料和生產工藝的限制，油墨的光譜曲線與理想顏色的光譜曲線有較大差距，印刷色域較小。

The main features of high fidelity printing technology include three aspects: first, in addition to black ink, C, m, y and other added color inks participate in color separation and neutral gray balance; Second, the printing color gradient change is closer to the real spectral color change effect than the four-color printing, and the printed matter has a strong sense of hierarchy and three-dimensional; Third, the printing gamut increases. Due to the limitation of ink materials and production technology, the spectral curve of ink is far from that of ideal color, and the printing gamut is small.

而高保真印刷中增加了新的色墨，用戶在使用高保真印刷時，可根據自身的實際情況，采取適當的添色方案，因為不同的原稿，需要表達的主題不同，要表達的色彩也不同，比如在印刷草莓時，紅色和綠色是色彩表達，此時就可以添加紅色和綠色作為基色。使用的油墨組合不同，對色域的擴充范圍也不同。比如以C、M、Y、K再添加R、G、B三色油墨印刷，二次色的R、G、B可以鮮艷地再現，其色域范圍得到了明顯的擴充。

New color ink has been added to high fidelity printing. When users use high fidelity printing, they can adopt appropriate color adding scheme according to their own actual situation. Because different originals need to express different themes and different color emphases. For example, when printing strawberries, red and green are the key points of color expression, You can add red and green as the base colors. Different ink combinations are used to expand the gamut. For example, with C, m, y, K and R, G, B three color ink printing, the secondary color R, G, B can be vividly reproduced, and its gamut range has been significantly expanded.

而高清晰度印刷技術則是為了盡可能提高印刷品的清晰度。印刷品的質量主要取決于單位面積上的網點多少和網點由小到大連續變化級數的多少。單位面積上的網點數量越多，印刷品的清晰度越高，網點的變化級數越多，印刷品的層次表現力越好，印刷品質量外觀越好。但是，印刷色域卻不會因此而有所增大，因為色域是由基色油墨的顏色確定的，只要基色油墨不變，印刷的色域便不會改變。目前，只有高保真印刷技術可以真正擴大圖像印刷色域，使印刷顏色更明亮鮮艷，更接近自然界真實效果。

High definition printing technology is to improve the clarity of printed matter as much as possible. The quality of printed matter mainly depends on the number of dots per unit area and the number of successive changes of dots from small to large. The more the number of dots per unit area, the higher the clarity of the printed matter, the more the number of dot changes, the better the level expression of the printed matter, and the better the quality and appearance of the printed matter. However, the printing gamut will not increase because the gamut is determined by the color of the primary ink. As long as the primary ink remains unchanged, the printing gamut will not change. At present, only high fidelity printing technology can really expand the color gamut of image printing, making the printing color brighter and closer to the real effect of nature.

3.關鍵技術

3. Key technologies

高保真印刷 的關鍵技術是分色，即如何將原稿中的顏色正確分解成不同的基色分量。目前常用的分色模式有兩種：一是用ICC提出的顏色轉換原理，即通過ICCProfile將原稿顏色轉換成印刷分色顏色，實際采用的是查表的方法。與四色分色相比，高保真印刷需要對顏色空間的色相區間進行合理的劃分，使油墨顏色匹配輸入色具有更小的同色異譜指數，提高匹配的精度。二是通過測量CMYK四色及其所疊印得到的RGB間色的三刺激值，用Neugebauer方程計算得到印刷分色顏色值，即網點面積率來進行分色，是一種數學模型。高保真分色的目標是使印品顏色盡可能接近真實景物的視覺感受。

The key technology of high fidelity printing is color separation, that is, how to correctly decompose the original color into different primary color components. At present, there are two commonly used color separation modes: one is to use the color conversion principle proposed by ICC, that is, to convert the original color into the printing color through iccprofile, and the actual method is to look up the table. Compared with four-color separation, high fidelity printing needs to divide the hue interval of color space reasonably, so that the input color of ink color matching has the minimum metamerism index, and the matching accuracy is improved. The second is to measure the tristimulus value of CMYK four colors and RGB inter colors, and calculate the printing color separation value, that is, the dot area ratio, by Neugebauer equation. It is a mathematical model. The goal of high fidelity color separation is to make the printing color as close as possible to the visual experience of the real scene.