CTP: Discussion on Wired Problems on Images (I)

March 08, 2019

In the current printing industry, CTP technology has been widely used. Special packaging and printing companies have invested heavily in CTP systems such as Creo, Heidelberg, Screen, and Agfa in order to increase their competitiveness in the market. However, the new technology brings us high efficiency, high quality, and high efficiency. Due to the low level of standardization, dataization, and standardization of prepress resources at various printing companies in China, there are some unsatisfying places in the convergence of this technology. Now, I will make a brief summary of the problems encountered during the use of this site (the introduction of the Heidelberg Dingsheng CTP system). I hope to help you.

The use of the process found that the problem of cable on the image is more prominent, summed up in these areas:

Software issues:

(1) Influence of the channel: In the tobacco label printing enterprise, the designers are more complex in the processing of images and graphics, and the processing of the images is more elaborate. When software for processing images and graphics is not handled in the same way as drafting software (for example, Coredraw and Photoshop do not have the same basis for processing image graphics), unexpected errors can occur. Stored the image processed in Photoshop as TIFF (with channels), and then imported it into Coredraw to make drafts and impositions. Then, after RIP interpretation was sent to the CTP plate making machine, we found that the four-color screen There will be a solid line passing through the network points of C, M, and K, and the image information will be destroyed. The corresponding position is a hollow white line in the Y version (as shown in the figure).

At the beginning of the analysis, it was thought that the laser head was scanning and the image information shot was offset. However, after the flat screen was tested, the screen was completely normal. Later, we communicated with design drafting staff to consider whether or not some special processing was performed when image processing was performed. It was learned that after the channel was operated, the channel was removed (without affecting the image processing output effect), and output was performed. The result is normal. After several tests, it is shown that the TIFF graph containing channels is different from Photoshop in Coredraw. After a RIP interpretation similar to Photoshop, some kind of transition occurs (there is a bit of processing for image graphics. The figure is still a vector) and the result produces this phenomenon. In view of this, to remind everyone, if you also use these two kinds of software to operate, we must properly remove the channel, then the CTP output.

(2) Consistency of color management: When a product was converted to CTP, it was found that the plate had a very thin line at the flat screen, and it began to feel that it was the influence of the channel. After contacting the designer, this was ruled out. Happening. Observing the thin line with a high magnification magnifier, it was found that the generation of thin lines is completely illusion, and the observed phenomena are as follows:

This creates an illusion, as if it were a thin line of dots. The overall Tiff image amplification detection is generated via the 1-BTIFF software, and the state is found to be exactly as shown. In other words, when the image is processed, the flat screen has been parsed into two kinds of very close color information, and it is communicated with the drafting staff that the flat screen image he will handle in Photoshop and the flat screen made in Coredraw. Spliced ​​together to output, due to the high resolution of CTP, such a subtle difference will also produce this error phenomenon. Finally, we conclude that the most fundamental reason is that the color management platform of our image processing software is inconsistent (image processing in Photoshop, large-scale file production and output in CorelDraw) because Acrobat reads the flat screen. The color was found to have an error of around 0.2, which led to interpretation in the CTP's high-precision RIP. Such subtle differences caused a miscarriage of file conversions. Therefore, in the use of CTP plate making, the production of the file must be carried out in the image processing software, spelling version of the software, as well as the software that generates the pdf format has a consistent color management system. The solution to this problem is to convert the image into a bitmap after completing the small version, or to convert the entire assembled large version into a bitmap, so that the integrity of the image information can be guaranteed. In addition, when making impositions, especially if there are retractable imposition methods for the common knife, it is necessary to ensure the tightness of stitching of the two small-size images, otherwise there will be thin lines.

(to be continued)

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