Digital proofing color management principle and implementation method
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The main purpose of digital proofing is to provide reference proofs for printing and to provide proofing basis for customers. A digital proofing system includes a printer, a set of digital proofing software (integrated color management function) and a measuring instrument.
In this process, achieving color management is the core and key to digital proofing.
Color management for digital proofing can also be easily summarized into four steps:
1 printer basic linearization; 2 production digital proofing paper profile; 3 packaging linearization file and profile file; 4 matching printer profile and printer profile.
This article takes the famous digital proofing software Best Screenproof developed by German software vendors as an example to introduce the principles and methods of digital proofing color management.
First, implement printer color management precautions
Summarized as follows:
1 color label should be printed in its original size.
2 The paper size is 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 it is used. If it is a Best Eye, the light source is about 2 mm away from the paper.
5 The resolution calculated by 5RIP is less than or equal to the resolution of the printout.
6 color matching method according to actual needs, Best developed a "Perceptual-absolute" matching method, suitable for photography use, especially the conversion and matching of large color gamut to small color gamut can get good results.
7 If re-linearization is required, re-linearize the selected proofing parameters such as paper, ink, printer, measuring instrument, and proofing software to be consistent with basic linearization.
8 Try to use high quality ink and paper to ensure that the color gamut of the printer is larger than the color gamut of the printing press. This is the basis for implementing color management.
Second, the basic linearization of the printer
1. Why do you need to do basic linearization of the printer?
The basic linearization determines the physical properties of the paper and the ink, optimizing the total inkjet volume of the printer and the amount of single-pass ink, that is, obtaining the largest possible color density with the smallest possible amount of ink for the printer paper.The creation of the profile provides the foundation and optimization features to establish the foundation of color management.
In fact, most inkjet printers are not linear output states. Generally, the maximum color density value is obtained when the total ink volume is about 50%. Thereafter, even if the ink volume increases, the color density does not change significantly. One is shown.
This causes the test patches of the Profile to be indistinguishable from the chrominance values of the higher regions, so it is important to determine the maximum total ink volume and the amount of single-pass ink by basic linearization.
For example, when an inkjet printer prints a yellow color patch, the maximum color density value can be obtained where the ink output is about 50%; even if the printer continues to eject ink in more than 50% of the area, the color density value is not Will increase again, but will make the output color a little red. The same happens when the printer prints magenta and cyan blocks.
Creating Such color patches are included in all color palettes of the profile. If the target is printed and measured with a spectrophotometer, the color density value changes significantly in the area where the ink ejection amount is 0% to 50%, more than 50%. In the area, the color density values change little, the measurement results are very similar, and these areas are produced.
Profile doesn't make sense.
If the printer is fundamentally linearized in advance, the range of small changes in output density will be ignored, and the chromaticity values represented by the remaining inkjet ranges will be evenly distributed, that is, the range of printed yellow patches will appear to be from 0. The average distribution between %-100% is manifested as a linear change in density, ie the printer input density value is approximately equal to the output density value. Obtained by a linearized printer
Profiles are more desirable than those that are not linearized.
The result of the base linear is saved in the file format of the extension bpl. When performing proofing output in Best Screenrproof, the relevant basic linear file must be required to limit the ink output of the printer.
2. How to perform basic linearization
Performing basic linearization only requires measuring the color density value, so it can be measured by any densitometer or spectrophotometer. Best Screenrproof supports online measurements such as DTP41, GretagMacbeth
Eye-one and BestEye, etc., and corresponding color targets for different measuring devices, users can open Color in the installation folder
Manager Charts find them.
The test steps are as follows:
1 Import all the color markers to be printed into the best.color Queue queue. If the measuring instrument is eye-one, you can import Total.
Ink Limit_BestEye, Ink Limit
Channel_BestEye, Lin6c_BestEye, and Quality Control_BestEye, respectively, for automatic printing and measurement of maximum total ink volume, single channel ink volume, linearization, and quality control;
2 Enter the basic linearization interface and set parameters such as measuring instrument, resolution, paper and ink type, as shown in Figure 2;
3 Print and measure Total Ink Limit_BestEye, the total ink volume measurement will be automatically generated and activated;
4 Print and measure Ink Limit Channel_BestEye and Lin6c_BestEye to obtain single channel ink volume measurement value, and automatically activate, the total ink volume and single channel ink volume can be applied to the subsequent color label printing;
5 Print and measure Quality Control_BestEye, check the linearization result, and require the interval line between each color block and color block to be clearly visible. There is no abnormality such as serious level, ink bar and penetration, which prompts the successful creation of printer basic linearity. Document.
Third, make a printer paper profile
Based on the linearized file produced and the amount of ink measured, the printout is used to create a color profile for the paper profile, such as IT8.7/3, which is measured and produced in Printopen or other ICC software. As shown in Figure 3, it is the wizard interface for Printopen.
Fourth, package printer linearization file and paper profile Best Screenproof provides a profile
The keeper plugin is specifically designed for the packaging of printer linearization files and paper profiles. The so-called packaging is to associate them and make them closely linked.
Five, object-oriented color management
The Best Screenproof software is used to match the profile properties of the printed and digital proofs, and the color gamut of the digital proof is used to simulate the color gamut of the print, which ultimately makes the print and digital proof colors look the same. We have obtained a profile file that reflects the characteristics of the printing process (Best Screenproof calls it a reference profile and a profile file that reflects the characteristics of color printers and printed paper (Best After Screenproof calls it paper profile), put these two profile files in Best Screenproof software, in a certain matching method (Render Intent), compiled and calculated, can print proofs very close to the print.
As shown in Figure 4, Best has object-oriented color management capabilities. In the reference profile option, you can select the CICK, RGB, LAB color space reference ICC file for conversion and matching of different color spaces, or in Best. Screenproof 4up CICCProfilesChecker Find a profile for checking the file color space below the Profiles directory, such as RGB Checker Profile, if you select it, when printing out, the RGB image in the file will be output as a simple green block, the user can easily find the problem; at the same time, there are two options in the lower part of the panel, according to the above method You can check whether each file has an embedded profile, or use the embedded profile instead of the reference profile set by Best.
After the color space conversion, a new CMM data set is generated, which records the mapping relationship of the data in the above two profile files in the intermediate color space, which is the matched data file.
By linearizing the printer and matching the profile of the printer and the press, you can print the output file arbitrarily in the created queue without having to make other color settings. This output file is based on color management for digital proofing. Therefore, in turn, it can be used as a basis for printing and a reference for proofing.