How much do you know about the common sense of metal four-color printing?
Metal four-color printing (four-colorprinting), using the subtractive method of three primary colors (yellow, magenta, cyan) and black for printing. If the printing process of using inks other than the four-color ink of yellow, magenta, cyan, and black to reproduce the color of the original manuscript, it should not be called 'metal four-color printing' but should be called 'spot color printing' or 'dot Color printing'.
Metal four-color printing is a lithographic printing method that uses the three primary colors of red, green, and blue and black pigments (inks or dyes) according to the principle of subtractive color mixing to achieve full-color reproduction.
In fact, due to the deformation error of the 'dots' in the printing process and the limitation of the visual recognition threshold, the colors that can be obtained by metal four-color printing are much less than theoretically.
Metal four-color printing process
Metal four-color printing process printing includes the use of four-color screening angle and four-color ink (three subtractive primary colors : Cyan, magenta, yellow, plus black) to reproduce the colors on the original. It can also be called process printing (printing primary colors) or CMYK printing (CMYK printing), which is a term named after printing inks.
Print color pictures through three subtractive primary colors (yellow, magenta and cyan) and black. The color image of the original manuscript used for printing must be separated into separate color separation sheets, and a black color separation plate is added to correct the cyan, magenta and yellow inks to improve the blackness of the printed image. These films are used to make the four printing plates required for metal four-color printing.
On the printing press, each printing plate must be accurately registered with other printing plates in order to obtain high-quality results. This is the industry standard printing method. CMYK is a color system widely used in computer printing equipment
Due to the limitations of color materials and production processes, the C, M, Y, K base color ink, there is a big gap between the spectral curve of printed color and the ideal color spectral curve. The color rendering effect of the secondary colors CM, CY, MY of ink overprinting, especially blue and green, is far from the ideal color. With the existing ink production technology, the ink performance is greatly improved, leaving little space. Therefore, it is difficult to expand the color gamut of metal four-color printing. For a long time, metal four-color printing has matched the density of the original with the density of the printed color. Measuring the density of printing colors is essentially measuring the amount of printing ink.
Printing color is composed of color components and neutral gray components. Under the condition of limited printing ink quotation, if neutral gray Too many components not only cause greater distortion of the brightness characteristics of the printed image, but also relatively reduce the amount of color components, resulting in a decrease in color saturation. The visual brightness of the metal four-color printing color is similar to a straight line, showing that the neutral gray component of the printing color is too much. Metal four-color printing emphasizes increasing the saturation of the copied color, at the expense of excessively sacrificing color brightness, which is another important defect of the metal four-color printing technology. Compared with the colors of natural sceneries, due to the above defects, metal four-color printing has heavy color reproduction, large tone distortion, unreal layering, and weak three-dimensionality.