Some things to be aware of in the adjustment and use of digital proofing
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In printing, proofing is a key process, which is the connection between the pre-press processes and printing. Its role has two points: First, check the problems in the pre-press process in order to find errors in time, make corrections, so as not to cause greater losses; second, control printing, which gives the printing process a customer-approved reference. Samples, printing need to control a variety of conditions, standard operation, so that the color, tone and proof of the finished product are not very different, to meet customer requirements. It can be seen that the proofing not only plays the role of checking the upper process, but also the function of controlling the lower process.
The main proofs are: screen proofing, laser proofing, traditional offset proofing and digital proofing. Screen proofing is done by adjusting the color of the screen so that the image on the screen is consistent with the color of the print. This type of proof is suitable for both American and advertising designers. The disadvantage of this type of proofing is that the color display is unstable and the difference from the printing effect is large, and the factors affecting the screen display are too much to control. Laser proofing allows you to adjust the shading of each color ink in the printer driver software. Use the output curve correction tool to make the ink color of the printer's primary color (CMYK) ink as close as possible to the actual primary color ink. This kind of proofing has no special requirements for the operator's professional skills, is easy to operate, and the data does not need to be converted, but it is far from the color and level of the printed matter. This type of proofing is mostly used in the advertising industry. Traditional offset proofing is the closest proofing method to printing. The material from the process to the use of the material is basically the same as the offset printing, so the color gamut of the two is the same, and the tone of the performance is the same. Conventional offset proofing has higher requirements for environmental conditions and process control. Therefore, the operational skills required for the proofing staff are also higher, and the stability control of proofing color and quality is not easy. This type of proofing is common in printing houses and some companies that specialize in proofing. With the development of printing technology, digital printing and CTP, the printing process is continuously simplified, and digital proofing is also widely used. It consists mainly of two parts: color management software and printers. Printers generally use inkjet printers, such as HP 5000, HP 10PS, EPSON 7600, EPSON 10000, etc., while color management software mainly performs color correction through ICC profile.
With the continuous improvement of printer ink, paper and color management software, digital proofing proofs are getting closer and closer to the printed matter. However, many printers are still difficult to use when using digital proofing as a printing proof. In addition to some printing factory printing conditions are not well controlled, printing operations are not standardized, proofing density and printing density are different, and some are caused by poor adjustment of printers and color management software.
In order to better use digital proofing, we need to pay attention to the following issues:
1. When choosing a printer, we have to consider the color stability of the printer, which is why the inkjet printer is now more. The color of inkjet printers is stable over a period of time, and no parts will gradually decay. In this respect, laser printers are more suitable for digital proofing.
2. The color gamut space of the digital proofing is wider than the printed gamut space, so that the printed color can be better displayed.
3. As a sample of the digital proofing simulation, it is best to print the sample, and do not use the traditional proofing sample. Because the condition control, printing principle and offset printing of traditional offset proofing have certain differences, the proofs of traditional offset proofing and printed matter are different. The digital proof proofs adjusted by using this sample will increase the difficulty of printing and proofing.
4. Select the paper used for digital proofing. Not all printer papers are suitable for digital proofing. When selecting digital proofing paper, you need to consider the color of the paper, the reproduction of the tone, and the whiteness of the paper.
5. When adjusting the color of the printer, consider the relationship between the printer and the paper and ink. When the paper or ink changes, the printer characteristic curve needs to be readjusted.
6. When the printing conditions, equipment, paper, and ink change, the color and tone of the printed matter will also change. At this time, the characteristic curve of the printing will also be readjusted.
7. Try to use the same spectrophotometer and feature file creation software to complete the printer profile and print profile to avoid deviations in digital proofs due to small differences between different spectrophotometers and profile creation software.
8. In color management software that can adjust printer density, it is important to adjust the printer density before making the printer characteristic curve. The closer the printer density is to the printing density, the smaller the color deviation will be.
9. Ensure that the observation conditions are consistent. The characteristics of inks for digital proofing are different from those of printing inks. Although the proofs of digital proofs and print proofs look the same, there is actually a metamerism phenomenon. When the lighting conditions change, the colors of the two colors are not guaranteed to be consistent. When using the spectrophotometer to test the color patches, the built-in standard light source is used. Therefore, when the sample is observed, the lighting is required, and the D65 standard light source is required. Otherwise, different color deviations will occur under different light.
10. Finally, pay attention to controlling the color difference (△E) between the digital proofing system and the actual printed matter, and control the color difference △E within 5.0. When △E=2.0, the human eye basically does not feel the difference in color; when △E=3.0, the human eye can only observe the difference in color; when △E=4.0, the two adjacent color blocks are more difficult to see. the difference.
Digital proofing has great advantages in terms of stability and ease of use, but it needs to be better used in printing. In addition to the experienced personnel to adjust the color of the printer at the beginning of the purchase, special personnel are needed. Maintain the printer and periodically correct the color so that digital proofing can play its part.