Print color management

This article hopes to explain the industry's misunderstandings about the Color Management System (CMS) and provide clearer explanations so that friends who can't get started can understand more.

Two sides of color management

Color management, which is often hung on people's lips, actually refers only to the management of the transfer of color spaces (such as scanners, computer screens, printers, etc.); however, printers have always tried to practice color consistency and repeatability, or Stability management is not included in the current popular color management. It is important to note that the two are different. If you focus on only one side of the actual production process, it is difficult to control the quality and stability.

Both must be balanced

The CMS mentioned so far is only able to achieve visually similar and consistent results when colors appear in different media (spaces), but it cannot manage to maintain stable reproducibility when colors appear in the same space. . That is, after a picture is scanned and actually printed, its color effect can be the most similar, but it cannot guarantee that the second printed piece can be similar to the first one. Thus extending to the use of the same film at different times of printing, whether the printed products can be consistent, which involves the process control of the printing process (processcontrol), but no one realizes that this is actually the color management One part. From this point of view, even if the color space transfer management can be maintained properly, it ignores the management of color repeatability and consistency, and may not necessarily achieve the desired effect when printing. Therefore, the color control of practice should be equal to both.

Mr. Fang Junyang, an engineer at the Printing Materials Testing and Analysis Center of the Association, pointed out that the color space transfer management can learn from the system whether certain colors can be reproduced by printing, predicting the deviation from the final printing, and when the printer actually prints, the printing master can It is easier and quicker to make proper adjustments on the press. However, in the process of adjustment, the test prints should also be tested, that is, to record the instrument measurement data, so that we can know the true capabilities of the machine.

Factors other than density

For printers, the quality of prints is digitized and recorded, and the density of dots per weight is considered to be controlled by most people because they believe that if they can control the density of outlets.

It is no wonder that Miss Wang, an application engineer at GretagMacbeth, said with a smile that when people in the printing industry use their color measuring instruments, they often only use the function of measuring density.

However, in terms of measuring the color of printed materials, in addition to the density, there are also known: 1 dot gain, if the dot is large, the density will increase; 2 the effect of color overlapping (trapping); 3 color deviation Contrast between (hueerror) and 4 colors. If you can master these data well, you will be able to know the characteristics of the printing process and thus improve the color stability of the printed matter.

How to communicate with color data

However, many people will encounter a question: The data measured by different color measurement instruments are different. Which data should be used? In fact, the color numbers measured by different color measuring instruments must be different. Therefore, when communicating with color data, several restrictions must be observed. First of all, the two sides need to use the same brand and model of color measurement instrument, in addition to measuring the same light source, even at the same temperature and humidity, etc., in order to affirm that the two sides can not go wrong. Therefore, it is more meaningful to use the same colorimeter to obtain the data.
Some companies rely on masters to control their quality. Therefore, if they later do the same prints and change the masters, it will be difficult for them to return to the past. Even if some companies measure color with colorimeters, they do not. To record those data, there is no evidence to follow next time, so taking records and statistics is also a necessary step.