How to Achieve Color Accuracy and Unity (I)

In platemaking, colors are extremely important. Accurate and repetitive reproduction of colors is fundamental to the survival of the industry. As a basic element of graphic design engineering, graphic designers use color as a tool for communication. What they are most concerned about is how to present the accurate proofing of the designed graphics to the customer; for prepress, from selecting and creating colors to maintaining color accuracy and Fidelity, the entire production process requires a high degree of reliability, prepress equipment is concerned about the interaction between the facing pages, color change requires prepress professionals in the process of how they want to create the color and printing A balance between limited color gamuts; in today's commercial printing, dedicated, highly automated printing equipment is used, it has a high degree of accuracy, and at high speed printing, the focus is on how to maintain color consistency and critical positioning However, with the advent of the Internet era, images that have traditionally been used only for printing have entered the era of electronic media. The electronic revolution has caused changes in the printing industry and has also caused changes in the pursuit of color. However, color is important and beautiful. It has extraordinary value in the process of plate-making. However, the requirements for color in the plate-making and printing industry are harsh. Therefore, how to achieve color accuracy and unification is the goal pursued by the industry. one.

What is color?

Fundamentally, the color of the human eye exists only as a feeling of the human eye and the brain. When light strikes an object or passes through it, it is affected by the surface quality of these objects. Then it spreads through space and is "seen" by our eyes. In this case, color is actually the translation of light from the eye and brain with different spectral energies into what we call the “color” phenomenon.

The color sensor in the eye is exposed to various frequencies and intensity of light. These sensors react photochemically with light. In response to light, the sensor sends a “signal” to the optic nerve of the brain. In the brain, the response matrix is ​​added together to become a reaction, or “color.”

What is color accuracy?

The color generation system must be able to reproduce a color and it can be copied many times without any change. The color of printed products should be precise, consistent, and repeatable.

The color fidelity is defined as the color accuracy of the specified or measured standard. In the printing industry, the standard colorants used are cyan, magenta, yellow and black. The first three colors are complementary, plus black, they make color printing "process" possible. Through the use of transparent ink and a tinting system, various sizes of droplets can be simulated to tone, and these colors produce images that allow the human eye to see "full color."

The ability to print a color accurately and repeatedly on a medium is a measure of the repeatability of the color. People are not only concerned with the repeatability of colors printed on the same media and devices, but they also care about the repeatability and accuracy of the colors between the printers. Although one can visually inspect the results of the printing process over various periods, the human eye is often not aware of more subtle changes that occur over time and may miss the presence of multiple copies of an image. Repeatability error. However, in the routine printing industry, it is necessary to obtain the same proofing effect when repeatedly outputting the same digital file. This is the demand for color accuracy.

How to determine the color accuracy?

After we know what the color accuracy and the color accuracy of people are, we should know how to determine the color accuracy. In general, in the graphic arts industry, people prefer to use Delta-E for measurement. This is a measurement method that describes “difference” and allows relatively easy measurement and calculation of color accuracy.

What is Delta-E Measurement? In platemaking, most color measurements are made with instruments. The instrument measures the value of CIELAB (a method of plotting the color information collected by the spectrometer). The comparison between colors is done by mathematically comparing two sets of CIELAB responses and by mathematically calculating the difference between them. The value used to describe the difference is called Delta-E. Although Delta-E can be derived using arithmetic methods, it is often described as the smallest difference in color and hue that the human eye can perceive. When describing the differences in printed samples, Delta-E values ​​proved to be very effective due to the connection between Delta-E and people perceptions. In the printing industry, changes in Delta-E between 3 and 6 are generally considered acceptable.

Although Delta-E measurements can be affected by viewer, ink, and media variability, some deviations are allowed here, and some variability in ink and paper quality can be tolerated. But there is always a certain standard. What is the standard Delta-E variability? During the printer's operation, the sampling interval for good commercial printing should not vary from more than 3 to 6 Delta-E units for the length of time it runs.

Generally speaking, the color effect in different Delta-E ranges is not the same: from 1.6 to 3.2, viewed from a certain distance, the color difference is basically invisible. This is usually considered as the same color; 3.2 to 6.5, The difference in color can be seen, but the color gives the impression that people are basically the same; from 6.5 to 13, the difference in color is visible, but it can be considered the same tone; 13 to 25, is considered to be different Hue that exceeds this value is considered a different color.

Based on this, older printers may experience greater changes than 3 to 6 Delta-E units, but whether this variability is accepted by the printer and the customer, it should be taken before the press starts to work. set up. When a print job goes beyond the company's variability standards, the smartest thing to do is to stop printing and try to determine the cause of the variability. When this reason is determined and corrected, the printing job can continue.

The pursuit of color accuracy

It can be said that the emphasis and pursuit of color accuracy is the most obvious in the plate printing industry. For a long time, in the plate-making printing industry, proofing has been highly valued by people as an important means of controlling color. Through proofing, various errors can be avoided. However, at present, people generally adopt a more traditional proofing method. In recent years, the print service market has undergone tremendous changes. The increase in work orders on the market, the reduction in the number of prints per order, and the reduction in the time required for printing have made traditional proofing methods face more severe challenges. Traditional lengthy proofing processes such as film making and printing are difficult to adapt to the ever-increasing demand for modern printing. Manual operation and chemical proofing are not only time-consuming and expensive, but also the printing colors are in an unstable state. The actual printing and printing Colors often have large in and out. It can be said that traditional proofing can no longer meet people's requirements for color accuracy. How to achieve more exciting and convenient proofing, and how to make the color more perfect in proofing, is the long-term pursuit of the plate printing industry practitioners.

With the advancement of human society and economic development, people are using more and more of various image prints. The most important factor in image products, color, is more important to users and designers. Especially those personal image designers, magazines, various types of advertising companies and prepress companies, their color requirements are more stringent. In the process of designing and producing the image product, mentioning the proofing process seems to only refer to the proofing of printing (contract proofing) before printing. Although the contract proofing plays an important role in the design and production of the entire color image product, it is not the only proofing required in the entire process. In fact, the design and production process of image products is composed of users, designers, platemaking centers, and printing plants. In the entire design and production process, there are two kinds of proofs that are indispensable, namely design proofing for designers and platemaking printing for the platemaking center (contract proofing).

Color is an important part of the image product. Designers generally rely on color to express their unique ideas on the final image product. Even if the designer has a good design idea, but if it can not be fully and accurately shown in the final product, then this design still can not be recognized by the user, and then even affect the user's trust in the designer, and follow-up business . For designers, they need to design proofing to help them design, not only for designers to communicate and communicate with each other, but more importantly to present their various design ideas to the user in a true and complete manner, and to the later stage. The printing production provides a reference. Therefore, they designed the proofing to complete the inspection of the color and text content, as well as improve the bidding effect of the design project. In the past, due to price factors, designers generally use the A3 format office inkjet printer for proofing. However, due to the limitations of the performance of such printers, designers can only use it to complete the inspection of the text content, and the inspection of the effect of color printing is not yet fully achieved. This will inevitably bring about various inevitable problems such as the increase of design cycle, increase of production costs, and lack of ideal bid effects.

Pattern proofing is an important process in the front-end printing process. It is provided by the plate making center to the designers and users. It is a powerful means of controlling the quality of the printed matter (mainly the color quality) and is used to check the quality of the plate making film. A means for the user to confirm, sign the use (that is, the contract signing). However, because traditional proofing has the disadvantages of unstable quality, high revision cost, long cycle, large investment, and unsuitability for the development of new printing technologies, the plate printing industry is constantly looking for new proofing methods to replace traditional proofing.