Cigarette Boxes Of Hinged Lid The Principle And Implementation Of Color Management in Digital Proofing

Cigarette Boxes Of Hinged Lid The principle and implementation of color management in digital proofing

 

The main purpose of digital proofing is to provide reference proofs for printing and to provide the basis for customers to sign samples, a digital proofing system includes a printer, a digital proofing software (integrated color management function) and a measuring instrument.

 

In this process, the realization of color management is the core and key to digital proofing.

 

Color management for digital proofing can also be simply summed up in four steps:

① printer basic linearization; ② Make digital proofing paper Profile; ③ Package linearized files and Profile files; ④ Match the printer Profile and press Profile.

 

Taking the Best Screenproof software developed by German software company as an example, this paper introduces the principle and method of color management of digital proofing.

 

First, the implementation of printer color management precautions

It is summarized as follows:

① The color label should be printed in full size.

② Paper size should be at least A3.

③ If the measuring instrument is DTP41T, the paper size is at least A1.

④ The measuring instrument should be calibrated when used. If it is BestEye, the distance between the light source and the paper is about 2mm during measurement.

 

The resolution calculated by RIP must be less than or equal to the resolution of the printed output.

 

The color matching method is selected according to actual needs, and Best has developed a "Perceptual-absolute" matching method, which is suitable for photography, especially the conversion and matching of large color gamut to small color gamut can obtain good results.

 

If you want to re-linearize, re-linearize the selected proofing parameters such as paper, ink, printer, measuring instrument and proofing software to be consistent with the basic linearization.

 

8 Try to use high-quality ink and paper to ensure that the color gamut of the printer is larger than that of the printing press, which is the basis for the implementation of color management.

 

Second, the basic linearization of the printer

1. Why do I need to basically linearize the printer

Basic linearization determines the physical properties of paper and ink together, optimizes the total amount of ink jet and the amount of single channel ink of the printer, that is, to obtain the largest color density as small as possible, provides the basis and optimization characteristics for the creation of the printer paper Profile, thus establishing the basis of color management.

 

In fact, most inkjet printers do not have a linear output state, generally obtaining the maximum color density value when the total ink volume is about 50%, after which the color density will not change significantly even if the ink volume increases, as shown in Figure 1.

This results in the Profile of the test color block can not distinguish the higher region of the chroma value, so the basic linearization to determine the maximum total ink volume and single channel ink volume is essential.

 

For example, when an inkjet printer prints a yellow color block, the maximum color density value can be obtained where the ink volume output is about 50%; Even if the printer continues to inkjet more than 50% of the area, the color density value will not increase, but will make the output color slightly red. The same situation also occurs when the printer prints magenta and cyan blocks.

 

The color blocks are included in all the color markers used to create profiles. If the markers are printed and measured with a spectrophotometer, the color density value changes significantly in areas where the ink jet volume is 0% to 50%, and the color density value changes very little in areas over 50%, and the measurement results are very similar, and these areas are not meaningful for making profiles.

 

If the basic linearization of the printer is carried out in advance, the range of small changes in output density will be ignored, and the chromaticity values displayed by the remaining inkjet range are evenly distributed, that is, the range of yellow color blocks printed out seems to be evenly distributed from 0% to 100%, which is a linear change in density, that is, the input density value of the printer is approximately equal to the output density value. A Profile obtained by a linearized printer will be more ideal than that obtained without linearization.

 

The basic linear results are saved in a file format with the extension ·bpl. When proofing output in Best Screenrproof, the relevant base linear file must be required to limit the ink output of the printer.

 

2. How to carry out basic linearization

The basic linearization only requires the measurement of the color density value, which can therefore be measured by any densitometer or spectrophotometer. Best Screenrproof supports online measurement, such as DTP41, Gretag Macbetheye-one, BestEye, etc., and provides corresponding color markers for different measuring devices. Users can find them by opening Color Manager Charts under the installation folder.

 

The test steps are as follows:

① Import all color labels to the best-color Queue. Assuming that the measuring instrument is eye-one, you can import Total Ink Limit_BestEye, Ink Limit Channel_BestEye, Lin6c_BestEye and Quality Control_BestEye. They are used for automatic printing and measurement of maximum total ink volume, single-channel ink volume, linearization and quality control;

 

② Enter the basic linearization interface, set the parameters of measuring instrument, resolution, paper and ink type, as shown in Figure 2;

③ Print and measure Total Ink Limit_BestEye, the total ink measurement result will be automatically generated and activated;

 

④ Print and measure InkLimitChannel_BestEye and Lin6c_BestEye, and get the measurement value of single channel ink amount, and automatically activate, the total ink amount and single channel ink amount can be applied to the following color label printing;

 

⑤ Print and measure the Quality Control_BestEye, check the linearization result, require each color block and the spacing line between the color block are clearly visible, there is no serious parallel level, ink bars and penetration and other abnormal phenomena, then prompt the successful creation of the printer basic linearization file.

 

3. Make printer paper Profile

Based on the linearized file produced and the amount of ink measured, the printout is used to make a color plate for a paper Profile, such as IT8.7/3, measured and produced in Printopen or other ICC software. The wizard interface for making a Profile for Printopen is shown in Figure 3.

 

Four, packaging printer linearized files and paper Profile Best Screenproof provides the Profile keeper plug-in, which is specially used for the packaging of printer linearized files and paper profiles, the so-called packaging is to associate them with each other, so that they are closely linked.

 

Five, object-oriented color management function

The Best Screenproof software is used to match the Profile feature files of printing and digital proofing, and the color gamut of digital proofing is simulated to make the color of printing and digital proofing look the same. We have obtained profiles that reflect the characteristics of the printing process (Best Screenproof called reference profile) and profiles that reflect the characteristics of color printers and printed paper (Best Screenproof called paper) After Profile, the two profiles are placed in the Best Screenproof software, in a certain matching way (Renderintent), after compilation and calculation, you can print out a very close to the printed proof.

 

Best features support for object-oriented color management. In the reference overview file option, you can select the reference ICC file of CMYK, RGB and LAB color space respectively for conversion and matching of different color Spaces. The Profile for checking the file color space can also be found under the Best Screenproof 4upC\ICC Profiles\Checker Profiles directory, such as RGB Checker Profile, if selected, when printing output, The RGB map in the file will be output as a simple green block, and the user can easily find the problem; There are also two options at the bottom of the panel to check whether each file has an embedded Profile, or to use an embedded Profile instead of the Best reference Profile.

 

After the color space conversion, a new CMM data set is generated, which records the mapping relationship between the data in the above two profiles in the middle color space, and is the matched data file.

 

After linearizing the printer and matching the Profile of the printer and press, you can print any output file in the created queue without any other color Settings. This output file is based on the color management of digital proofing. Therefore, in turn, it can be used as a basis for printing and sample reference.

 

(Author: Department of Printing and Packaging, Wuhan University)