1. Definition

高保真印刷是相对于四色印刷而言的，通过在C、M、Y、K四色印刷的基础上增加红、绿、蓝、橘黄等颜色油墨的方法来改善印刷颜色的再现性、真实性。

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.

高清晰度网点是指高于250lpi的调幅网点，即100%网点直径小于125μm的调幅网点，以及等效直径20μm以下的调频网点。以提高印刷品清晰度为目标，采用高清晰网点进行的印刷称为高清晰度印刷。高清晰度印刷技术可有效缩小网点的间距，提高印刷品的清晰度和层次表现能力。

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

高保真印刷技术的主要特征包括三个方面：，除黑墨外，C、M、Y及另外增加的彩色油墨均参与彩色分色和中性灰平衡;第二，印刷颜色阶调变化比四色印刷更接近真实光谱色的变化效果，印刷品的层次感、立体感强;第三，印刷色域增加。上海印刷厂在四色印刷中，由于油墨材料和生产工艺的限制，油墨的光谱曲线与理想颜色的光谱曲线有较大差距，印刷色域较小。

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，用户在使用高保真印刷时，可根据自身的实际情况，采取适当的添色方案，因为不同的原稿，需要表达的主题不同，要表达的色彩也不同，比如在印刷草莓时，红色和绿色是色彩表达，此时就可以添加红色和绿色作为基色。使用的油墨组合不同，对色域的扩充范围也不同。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可以鲜艳地再现，其色域范围得到了明显的扩充。

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.

而高清晰度印刷技术则是为了尽可能提高印刷品的清晰度。印刷品的质量主要取决于单位面积上的网点多少和网点由小到大连续变化级数的多少。单位面积上的网点数量越多，印刷品的清晰度越高，网点的变化级数越多，印刷品的层次表现力越好，印刷品质量外观越好。但是，印刷色域却不会因此而有所增大，因为色域是由基色油墨的颜色确定的，只要基色油墨不变，印刷的色域便不会改变。目前，只有高保真印刷技术可以真正扩大图像印刷色域，使印刷颜色更明亮鲜艳，更接近自然界真实效果。

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.关键技术

3. Key technologies

高保真印刷 的关键技术是分色，即如何将原稿中的颜色正确分解成不同的基色分量。目前常用的分色模式有两种：一是用ICC提出的颜色转换原理，即通过ICCProfile将原稿颜色转换成印刷分色颜色，实际采用的是查表的方法。与四色分色相比，高保真印刷需要对颜色空间的色相区间进行合理的划分，使油墨颜色匹配输入色具有更小的同色异谱指数，提高匹配的精度。二是通过测量CMYK四色及其所叠印得到的RGB间色的三刺激值，用Neugebauer方程计算得到印刷分色颜色值，即网点面积率来进行分色，是一种数学模型。高保真分色的目标是使印品颜色尽可能接近真实景物的视觉感受。

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.