The two-color printing design simply refers to the process of reproducing the original document by using a color separation processing technique for one image and using a combination of two different color inks. In general, in the C, M, Y, K four-color printing plate, the black (K) printing plate is combined with any of the other three color (C, M, Y) printing plates, because of the dark printing plate in the dark tone. The tone distribution is stronger and enhances the tone contrast of the image. In the bright tone, the black tone information is weakened, and the color levels of C, M, and Y colors are strong. This allows the layered and color changes of the image to be superimposed, making it easier to reproduce the original color levels and levels of the image. Adjust information. The combination of the three colors C, M, and Y, although the color range is larger at the bright tone, lacks the image level at the dark tone, resulting in a smaller hue contrast of the image, making it difficult to reproduce the original effect of the image. Therefore, two-tone printing design mostly refers to the combination of black and other spot colors.
The key to the design of two-color printing lies in the two-color processing of the image. To fully protect the original level and tone information of the image, the best tool to achieve this color effect is to achieve the desired color effect by changing the relationship between the two-color combination. Is a dual tone in Photoshop image processing software. Duplexing is achieved by adjusting the curves of two different colors to achieve the image effect that the graphic designer wants. That is, the two-color printing design is not a direct reduction of the four colors of C, M, Y, and K (minus two channels, two channels are reserved), but is based on the structural principle of the gray-scale mode image itself. Adjust the two colors with the curve tool and rediscover the combination at different levels.
The correct way is:
1, to ensure that the original image is RGB mode. Instead of the CMYK mode (because the RGB mode is based on the color mode adopted by the optical principle, and the CMYK mode is determined by the absorption properties of the paper ink, the RGB mode has a wider color range than the CMYK mode. The RGB mode can express many colors, especially Bright and bright colors, that is to say, RGB mode can display richer image hierarchy and tone information than CMYK mode.
2. Then change the RGB mode to Lab mode and delete the two color channels a and b, leaving only the L luminance channel. Then convert the L-luminance channel mode to Grayscale gray-scale mode (because Lab mode has good features, it contains the widest range of colors, making up for the lack of two color modes of RGB and CMYK. That is, the image is transformed by the Lab mode. The grayscale mode can preserve the gradation information of the original image more completely than the RGB and CMYK direct transition grayscale modes.
3. Use a two-tone tool to design the image in grayscale mode. In the process of using the two-tone tool, you can adjust the two-color curve to achieve the ideal two-color effect according to your design needs. Then the two-color design file is stored as a Photoshop EPS file format. In this way, the task of color separation of the two-color printing design image is completed, because the technique of the two-color printing design lies in the two-color design of the image.
There are graphic designers who lack understanding of the principles of printing technology and are not well-versed in the performance of Photoshop software. So the wrong method is often used for two-color printing designs. There are two main forms:
One is to directly select the image components of two corresponding channels in the four color channels of C, M, Y, and K, or to select two channels in which the image layer is rich, and output the plate. This method only uses image local gradation information in a one-sided manner and sacrifices other channel's hierarchical information, which will inevitably lead to image distortion.
Second, in order to enhance the gradation information of some channels, the CMYK mode of the image is first converted to the Grayscale gray mode, that is, the four-color channel is merged into a single-color channel, and then it is switched back to the CMYK four-color mode, and finally two are selected. Corresponds to the channel's image components and outputs the plate. Compared with the method one, this method still causes some levels of image in some channels to be improved, but it will still lose the level information of other channels, resulting in image distortion.
The basic elements of layout design are composed of images, vector characters, decorative lines, and color blocks. This requires that the image with two-color design must be combined with the corresponding explanatory text, and the text, decorative lines, and the text in the composite software must be combined. The color of a color patch is defined by its own color palette, so the key to two-color printing design skills is:
The Photoshop image bi-color imported in the build software (such as Pagemaker, Freehand, etc.) must be used as the bi-color in the build software. For example, the specific colors of an image after the Photoshop duotone tool design are black and PANTONE 1915. When this image is placed into the PageMaker software, it will be automatically brought into the image in the color palette of the Pagemaker software. The two spot colors black and PANTONE 1915, when defining text, decorative lines, and color blocks in the Pagemaker software, must use only black and PANTONE 1915 spot colors to ensure that the final output of the book is double-colored.
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