The working process of Weatherproof Matte Inkjet Sticker Paper is discussed in detail

The working process of Weatherproof Matte Inkjet Sticker Paper is discussed in detail

(I)ICC feature file

In the process of color printing, it is common to hear prepress operators say: we do a very good plate, but it is a pity that this batch of work is ruined when printing. And the printing operator has another discussion, what is the printing plate! The place is not deep, the place is not shallow, it is impossible to print!

 

Why are there these two different sounds? The reasons are as follows:

(1) The color on the computer screen is different from the color printed on the paper:
(2) The contract proof signed by the customer is inconsistent with the printed proof;
(3) The influence of various materials and equipment on color.

 

It seems that color management is first a color space problem, that is, based on which color space to control the color. Monitors, digital cameras, scanners, etc. all work in the RGB color space; The press machine and printing press all work in the color space of CMYK. When the same image is output on these devices, the final color effect may be completely different. This is because they are in different color Spaces.

 

Since RGB and CMYK are device-related Spaces, it is necessary to realize the conversion of spatial color patterns of different devices, so as to ensure that the color of the same image from input, display to output is matched as far as possible, and finally achieve the consistency between the original manuscript and the replica. It needs to be built in a color space unrelated to any specific equipment, materials and processes.

In the color management technology, the chroma space of CIEl976Lab is adopted. The colors on any device can be converted to this space, and then the color matching conversion is carried out.

 

In order to more clearly illustrate the role of CIEl976Lab chroma space, let's take a look at an example:

 

In actual life, we often go to the farmers' market to buy food, we will find that there is a weighing platform at the exit of the farmers' market, and it is the only one, which is set up by the industrial and commercial departments in order to manage the farmers' market and prevent traders from being short of weight. All the buyers of vegetables can go to the weighing platform to weigh if they feel that the food they bought is not enough. This is a standard scale. This standard scale has nothing to do with any vendor's scale, and any vendor must rely on this scale as the standard.

In color management, to present the colors on one device to another device in high fidelity, it is necessary to understand the characteristics of color presentation on various devices. Since a color space independent of the device has been selected, that is, the CIEl976I plus chroma space, the color characteristics of the device are shown as: the value of the color description of the device and the color value of the "universal" color space has a certain relationship, that is, the color characteristics of the device (profile). Or ICC feature file.

 

ICC feature files are classified into input device, display device, and output device.

Note:

①RGB color space

A color space composed of a collection of colors mixed by three primary colors: red, green and blue. Scanners and monitors are made of red, green and blue primary colors. RGB color space is a device-dependent color space, that is, the colors they produce are related to the specific device used. Color mixing rules in RGB color space conform to the color light plus color method.

 

②CMYK color space

CMYK color space is the space formed by color materials, in line with the principle of color subtraction. The CMYK color space is also device-specific.

Note: CIEl976Lab chroma space
CIE: French prefix of the International Commission on Lighting
L is for brightness of color
a is the degree to which the color is more red than green.
b is the degree to which the color is more yellow than blue.
Note: ICC is the Intermatconal color consoertion [next]

 

(2) Three Cores of the Color Management System (3C)

To achieve the desired effect, the color management must be carried out under a series of specified processes, which consist of three elements: Calibration, Characterization and Conuersion. They are the three core of color management.

 

1. Equipment calibration

In order to ensure the stability, reliability and sustainability of the color information transmission process, it is required to compare the input equipment, display equipment and output equipment to ensure that they reach the best working condition.
Input correction: It is to correct the brightness, contrast, black and white field (RGB balance) of the input device. A corrected scanner, for example, should obtain the same image data whenever it scans the same manuscript.

Display correction: make the display card according to the color data of the image data, accurately display the color on the display.
Output correction: the correction of the phototypesetter is based on the correct image of the display; The calibration of the printing press and the proof machine must make the paper, ink and other printing materials used in the equipment meet the standards.

 

2. Equipment characterization

As mentioned earlier, one of the core aspects of the color management effort is the establishment of the device file, which acts as a standard and is the bridge between the two color Spaces (PCS).

Simply put, the color management system transfers the data file to the color space of the characteristic file according to the characteristic file of the input device, and then transfers the color information of the data file to the color space of the output device according to the characteristic file of the output device (display, prototype), so as to ensure the consistency of color restoration in the workflow.

 

3. Color conversion

The third core of color management is color conversion module (CMM), which is used to interpret the device feature file, and according to the device color described in the feature file for color data conversion of different devices.

A basic principle of color conversion is that the same color is guaranteed to remain the same color on different devices. To achieve this, there needs to be a device-independent color system to measure colors on each device, and any device-specific color space can be represented in this color space. If different device-related colors can all correspond to the same point in the device-independent color space, then the conversion between them must be accurate. During color conversion, the color data is first converted to. The color value of PCS is then converted to the color value of other devices as needed.

 

The following illustrates the application of these three cores in color management through the specific production of ICC feature files of input and output devices:

● Make ICC feature files for input devices

(1)IT8 standard color code

The Kodak IT8.7/1 IT8.7/2 standard color code (hereinafter referred to as the color code) is generally used if you want to make ICC feature files for input devices.

IT8.7/1 and IT8.7/2 color scale is suitable for color calibration of input devices (scanners and digital cameras), IT8.7/1
The materials used in IT8.7/2 and IT8.7/2 are color transparent positive and color photographic paper, respectively. IT8.7/1 is suitable for input color correction of transmission scanner; IT8.7/2 is suitable for input color correction in reflection scanners.

 

The IT color code consists of four parts:
① Sample the color area. This part consists of 12×12 color blocks. It is divided into dark, middle and light toning blocks according to the column, and each part has four saturation changes.

② Color ladder ruler. There are seven columns in this part, three of which represent cyan, magenta and yellow respectively. The other three columns are red, green and blue; The middle column is neutral.

③ Neutral grey ladder ruler. At the bottom of the color scale are the twenty-second neutral gray scale varying by space. It is mainly used for basic correction of input equipment.

(4) Optional areas. Different manufacturers can arrange three columns according to their needs, such as characteristic colors. The whole color scale contains 286 color blocks. These color blocks are the standard color blocks to establish the scanner ICC feature folder. They represent the whole color gamut quite completely, and each color block contains a standard chrominance data.

 

(2) Preparation of scanner ICC feature files

 

The production process of scanner ICC feature file is as follows:

① Calibration
The purpose of calibration is to adjust equipment (such as scanners, monitors, printers and presses) to a standard state to ensure that it meets manufacturing specifications. Most of the equipment will be corrected before leaving the factory, but during the use of the equipment, there will be changes such as environmental changes; Equipment aging and other reasons affect the quality of color reproduction, so calibration is very important to reproduce color. All equipment must be calibrated before it can be used.

After the scanner is turned on, the scanner is preheated, and then the scan driver software is run. First, the IT8 manuscript is scanned, and the brightness, contrast, focal length, gray balance and intermediate adjustment of the scanner are corrected by the gray ladder rule at the bottom of the IT manuscript.

For example: ensure the first level of the gray ladder in the scanned image. The RGB value is kept between 150 and 255, the RGB value of level 22 (the dark part) is kept between 0 and 5, and the RGB value of level 11 in the middle part is right of 125.

If the values of R, G and B of the scanned image are inconsistent, it indicates that the scanner is biased in color. It is assumed that the RGB values of the 11th level of the intermediate tone are measured as R=118, G=125 and B=125. In this case, the intensity of red can be increased to maintain a balance with green and blue. This can ensure that the color of the scanned image is smaller and the color is pure.

 

② Scan the IT8 color scale
According to the reflection of the scanner; Transmission type can be IT8.7/1 color scale or IT8.7/2 color scale scan. Unscreen, sharpen, level, and other color management-related options in the scan menu, and then save the scanned RGB image.

 

③ Generate the ICC feature file in the ICC feature file creation software
There are many software for making feature folders, such as the software of Heidelberg Company and the software of Agfa Company.
Run ICC feature file making software, open the standard file containing color block chrominance data and the scanned image file in the software, the software will compare, correct and optimize the RGB data in the image file with the Lab chrominance data of color block standard, so as to obtain the scanner feature file, and finally save the file. The ICC feature file of the input device is created.

In this ICC properties file i 'records the basic properties of the scanner to reproduce colors. Different scanners have different ICC properties files. As you can see, the IT8 color scale is used as a ruler to measure the accuracy of the color in the process of making ICC feature files.

Output the ICC feature file of the device

 

(1) IT8.7/3 digital standard color code
IT8.7/3 digital standard color code (hereinafter referred to as color code) is essential if you want to make ICC feature files for output devices. IT8.7/3 color scale is an electronic file, suitable for CMYK four color display for the output device.

The IT8.7/3 color scale contains a total of 928 different color blocks. The color data of these color blocks are CMYK data, and the coverage rate of CMYK dot of each color block is different. When different output devices output IT8.7/3 color scale, the printed 928 colors represent the color performance capability of the output device. Devices with strong color performance can perform fine differences between blocks; And the color performance of the poor performance of the equipment between the color block difference is less, the small difference between the color block will be indistinct. The ability of the output device to reproduce the IT8.7/3 color scale represents the output accuracy of the device.

 

The IT8.7/3 color scale contains the following different types of areas:
① dark color block area.
② Overprint color block area (check ink overprint effect j
③ Saturated color block without black.
④ contains 20% black saturated color block area.
⑤ Grey areas made up of CMY or CMYK (check grey balance).
⑥ Field color block color area (to check the field density).
⑦CMYK ladder scale (check network coverage).

 

(2) Output the process of making the ICC feature file of the device

This section uses the printing device as an example to describe how to make the ICC feature file of the output device.

 

① Calibration
The control bar tool was used to calibrate the printing equipment, mainly in terms of field density and dot coverage, prior to formal printing of the IT8.7/3 color scale. The environment and production conditions of the press are required to be stable. For example, field density and dot coverage in formal production must be consistent with the IT8.7/3 color scale so that the resulting ICC characteristics file correctly reflects the color characteristics of the press.

 

② Print IT8.7/3 color scale
The IT8.7/3 color scale output, printing to obtain proof. In addition, the film output, printing process adjustment to the standard state.

③ Generate the ICC feature file in the ICC feature file creation software

Generally, it is an online automatic measurement. Scanning spectrophotometer is driven to measure the chromaticity of IT8.7/3 printed proof according to the prompts. After the measurement, the software will accurately correspond the chromaticity data measured to the CMYK data of the color block in the color scale. . Save the ICC properties file.

Unlike a scanner, which has only one ICC characteristic file, a press may have multiple ICC characteristic files. The reason is that changes in paper, ink, dot, and environmental conditions can affect color, so multiple ICC characteristic files must be made for different paper and ink combinations to meet production needs.

If each device associated with color copying has an ICC property file, the necessary foundation is laid for consistency in color copying. The importance of ICC properties files in color copying is illustrated below only with soft screen proofing. One of the functions of proofing is to check the quality of the color on the proof. If you can find errors before the formal printing, you can reduce the cost. Can you preview the actual printing color effect through the display in advance?

The mechanism of color reproduction is completely different between display and printing. The display screen produces red, green and blue, which are produced according to the mixing mode of color and light, while the four inks of yellow, magenta, cyan and black used in four-color printing are produced according to the mixing mode of color materials. The gamut of the two devices is also different. As a result, the colors seen on the monitor are actually quite different from the colors on the final print.