How to adjust the color of external electronic documents?
Time:2022-12-06
Views:2629
Selection of processing scheme
Since the color separation Settings of external electronic documents are not suitable for commercial rotary printing, we propose two solutions to solve this problem.
1、Re-color all the images in the original file
Re-color all the images of the original file, that is, the images adjusted by the customer are converted to RGB format, and then re-color according to the printing suitability requirements of commercial rotary presses.
However, the client sent PDF files, printing companies can not adjust the color themselves, contact the client will bring trouble to the client, and they have to contact the advertising company that produces the electronic files, but the advertising company is not particularly familiar with the suitability of printing, so the communication is not smooth. In addition, this journal is a weekly, the printing time is relatively tight, if you want to readjust, the time is not allowed, and after the final readjustment will also bring hidden dangers. Generally speaking, this method is not advisable.
2、Adjust the color by adjusting the CTP output curve
2、Adjust the color by adjusting the CTP output curve
Through the analysis of the printing measurement and control strip on the printing proofs of the last issue of the weekly, we obtained the following data: the medium adjustment dot increase value of the commercial rotary printing press is about 25%, that is to say, the dot percentage of 50% on the printing plate is about 75% after printing, and the dot increase is larger.
Open the client of Fang Zang Smooth flow, select output management in the management tool, click the curve management, and pull out the CTP output curve when using a sheet offset press. It is found that the curve is basically a straight line with the horizontal coordinate of 45°, the dot percentage of 51.7% in the prepress file is 50.0% on the CTP version.
Therefore, if such a CTP version is directly printed on a commercial rotary press, the following problems may occur: the amount of ink is small, the middle color of the image is appropriate, and the density of the dark tone is not enough, the color saturation is not good, and the image contrast is small; If you increase the amount of ink, the saturation of the dark tone is appropriate, the light tone, the middle tone will be due to the serious increase of dot, resulting in too deep color, the picture appears gray, no level, can not catch up with the digital proof.
Based on the above analysis, we propose the following solution: the dot increase curve of commercial rotary press is obtained through the printing measurement and control bar on the printing proof of the last issue of weekly. According to the curve, the output parameters of CTP are reset to compensate for the dot increase of commercial rotary press.
In order to save the amount of dot increase for rotary printing press, we made a unified adjustment to the four-color printing curve by analyzing and estimating the printing measurement and control strip on the printing proof of the last issue of weekly. Select "Use the same data for all curves" and adjust the output value at the input value of 25% from 24.3% to 32.0%, from 51.4% to 60.0% at 50%, and from 76.6% to 82.0% at 75%. Since the output curve of CTP is the inverse function of the printed curve, after such adjustment, The CTP version of the output is about 9% lower in the middle tone, 7% lower in the light tone, and 5% lower in the dark tone.
Steps of Implementation
In order to save the amount of dot increase for rotary printing press, we made a unified adjustment to the four-color printing curve by analyzing and estimating the printing measurement and control strip on the printing proof of the last issue of weekly. Select "Use the same data for all curves" and adjust the output value at the input value of 25% from 24.3% to 32.0%, from 51.4% to 60.0% at 50%, and from 76.6% to 82.0% at 75%. Since the output curve of CTP is the inverse function of the printed curve, after such adjustment, The CTP version of the output is about 9% lower in the middle tone, 7% lower in the light tone, and 5% lower in the dark tone.
After adjustment, we carried out the first trial printing. The printing effect is good, which can not only ensure the saturation of the dark tone, but also meet the level of the middle tone, but also highlight the bright tone. The printing operator also reflects that it is easy to follow the color, which shows that the adjustment direction is right.
By comparing the first printing proof with the digital proof, we found that the medium dark of the printing proof was very close to that of the digital proof, but the light tone was somewhat bluish (mainly reflected in the skin color of the characters). The reason may be that the paper color was slightly bluish. Therefore, we adjusted the printing curve of the M plate by using the principle of complementary color, and set the output value at 20% of the input value of the curve. Adjusted from 26.0% to 23.0%, that is, M version of the dot percentage of bright tone than other color version more than 2% ~ 3%. According to the adjusted curve, the second trial printing was conducted. After printing, the brightening and toning characters‘ skin color was obviously better, but the highlight of the M version was somewhat lacking.
Therefore, we made a third fine-tuning of the printing curve, adjusted the printing curve of the M plate, adjusted the output value of the curve at the input value of 5% from 8.0% to 7.0%, from 15.0% to 14.0% at 10%, and from 21.0% to 20.0% at 15%. That is to make the CTP version of 5%, 10%, 15% of the dot percentage than the original 1%. According to the CTP output curve adjusted for the third time, the CTP plate was output and printed on the machine. The printing effect was very good and the customer was very satisfied.
We have tracked and monitored the printing of this issue of weekly magazine. The printing effect is stable, the color saturation is high, and the order and level are restored well. The customer is very satisfied.
To sum up, if the printing enterprise received external electronic documents are not suitable for the current printing conditions, may wish to take the method described in this article to adjust the printing curve to try, may get unexpected results.
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Anna Zhang