Color Mark Application (5)

Need to zero on the paper when measuring the color scale?
No need. In the process of image duplication, paper density and paper color are important reference data and should therefore be included in the density measurement process. The measurement of the paper density should be carried out using four densitometer filters at the same time, and it is used in practice to calculate other printing characteristics parameters.

Is using a density meter the only way to measure a color scale?
The role of the color standard is to allow operators and other relevant personnel to measure and communicate the changes that occur during the printing process, so the density meter is not the only measurement tool. This is because the most effective way for the operator to change the appearance of the image while the printer is printing or printing a job is to change the ink balance by controlling the ink supply system or the fountain solution. The key measurement factors that characterize the success of this control are density values ​​and dot gains. The latest colorimeters and spectrophotometers can use the built-in computer calculations to obtain the density and dot gain values ​​required for the press operation. . However, compared to this, the density meter is probably the most effective and lowest cost measurement color standard, and it is also the most intuitive tool.

What is the difference between color labels for production, color labels for proofing, and GCA/GATF Proof Comparator?
From a technical point of view, these three colors are very similar. They all have color patches that measure print characteristics, such as solid ink density patches, dot gain at 25%, 50%, and 75% tone values, trapping, gray balance, and ghosting. The main difference is that the GCA/GATF Proof Comparator has a flesh-colored and light-colored graphic palette that helps visually identify color shifts. The GCA/GATF Proof Comparator and GATF proofs also include 25%, 50%, and 75% tones of overprinted patches.
From an application point of view, these three colors are very different. The color scale for production should be as narrow as possible (approximately one-fifth of an inch) to ensure that it can be affixed to the free space of the printing plate. Each object in the color plate is closely arranged to form a long row. The color code for proofing will not have the above constraints and limitations due to different uses. It is approximately 1.25 inches wide and contains larger objects and additional control elements. Proofing color code is often used for proofing on a printing press. The GCA/GATF Proof Comparator was developed specifically to detect the quality of pre-proof proofs. The GCA/GATF Proof Comparator has a width of 2.25 inches and contains all the objects in the proof color patch to detect the reproduction of printing primaries, overprints, gray balance color patches, and graphic elements.

What is the number of screen lines and dot shapes on the color scale?
There are two basic principles to follow when choosing a screen number for a color code:
First, it is recommended that the number of screens on the color code should be the same as the number of screens used for the print job. This is mainly because the amount of dot gain will be affected by the number of screens. The higher the number of screens per inch, the larger the dot gain. The use of the same number of screens as the actual production to screen the color code can truly reflect the operating conditions of the printing press and is consistent with the halftone color separation method.
Second, it is recommended to use a slightly higher screen number than the print job. This principle is based on the fact that due to the finer number of screens, the color scales are more sensitive to changes in the printing process, and can be changed faster than actual production through dot gain and dot sharpening, so warnings can be exercised. People make necessary process adjustments before the image begins to change visually, reducing waste.

Whether or not a color code with a higher number of screen lines will be more sensitive to process changes, investigations on this issue show that this principle is correct in theory:
l The number of screen lines between 133 lines per inch and 150 lines is the least sensitive to errors.
l When measuring color scales, the method used and the inherent measurement differences on the equipment can be used to override any differences in the number of color-coded screen lines.
There are currently two different views on the discussion of dot shapes. Some people think that color patches should use dot shapes that match the color separation film to provide the best correction. It has also been suggested to use round, square, and elliptical dots, each of which has its own advantages, and the difference in dot reproduction caused by dot shapes is small, and it is the same as the number of lines added to the measurement process. The change is much smaller than the change brought by copying or copying the color film.
The following method is recommended:
l It is more important to consistently use the same number of color-coded screen lines than to correlate the number of color-coded screen lines with the number of screens actually produced. With the continuous accumulation of experience, operators, managers, etc., have begun to associate objective measurements with the appearance of images. Using color scales with different numbers of screens can hinder the understanding of these changes, introduce confusion, and increase the complexity of quality control.
l If possible, a color patch that matches the actual number of screen lines can be used. The number of screens of the color code is the same as the number of screens of the color separation sheet printed in parallel with it. When the measurement is performed, the visual appearance of the image can be easily associated with each part, and the confusion caused by the difference in the number of screen lines can be reduced. The smallest.
l Color patches can use any dot shape, as long as the dot shape is consistent across all applied films and all objects that contain these patches.

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