A Color Control Method For Printing Bottle Wine Bags With Handles

A color control method for printing Bottle Wine Bags With Handles

 

Color control is a subject often involved in printing image reproduction technology. It is an accepted fact that color proofing should be used as a quality control tool to obtain qualified standard printing proofs and then control the press to produce stable hue. Although the printing parameters may vary significantly, as long as the printing press can be controlled, the color of the printed image can be stabilized by changing the field density. The control of the printing press can be carried out through the reasonable use of densitometer, which can not measure color, but can be used to control the stability of color.

First, the method of color control

The purpose of color control is to produce a product with no deviation in hue and saturation throughout the printing process. In order to maintain the consistency of product quality, it should be effective to control the consistency of field density, but this method is only an early method for color reproduction with single-sheet presses, and is wrong for four-color presses. In fact, on the contrary, the operators of four-color presses tend to control the hue of the press, color saturation and compensate for many variables in the printing process by changing the field density.

 

There are many variables affecting the quality of the printing press, and more than 100 printing parameters are taken into account. To properly control a press, each printing unit can set adjusting knobs for dot increase, dot distortion, ginning, overprinting and other important variables, making the console of the press as easy to observe and adjust as the control panel of an aircraft. In fact, each printing unit has only two main controls, one for ink delivery and one for water delivery.

 

Two, control the steps of color
At present, in order to make printing color reproduction correct method is to follow the following sequence:

(1) Control printing conditions, determine the correct printing color sequence, optimize the field density of printing, so as to achieve the maximum printing contrast; When the amount of ink to dot increase and overprint the impact of contradiction, should be considered in the compromise by adjusting the amount of ink so that the overprint color balance.

 

(2) Calibration color proofing system: using visual observation method calibration color proofing, so that it consistently simulates the printing control conditions that have been determined above.

 

(3) Color proofing for a set of color separators: use the calibrated proofing method and control means to produce correct and consistent proof.

④ Determine the standard proofing proof: select the visual appearance in line with the expected requirements of the proofing proof for standard proof.

 

⑤ Adjust the four-color offset printing press: the overprint screen produced on the normal press should be visually consistent with the hue and saturation of the standard proof.

 

⑤ In order to get a visually consistent product, adjust the field density in the process of operation: even if the dot increase, overprinting, dot deformation or double shadow may be produced, the hue and color saturation of each print should be the same. The appearance of each print should be visually identical to that of a standard print proof.

 

Three, the importance of color proofing

In order to make the printing effect and proofing visually consistent, the proofing method should be calibrated to the printing press in the printing production, and then the printing press should be adjusted to make the printing effect match the proofing proof. This leaves the reader with the impression that attempts to control color steps are like chasing our own tail around a circle, but practice tells us that this approach is successful.

 

Califried pointed out in 1983, "For a color, we can describe it with language and quantify it with measurement methods, but we must also use a sample as a reference to describe the characteristics of the color. In practice, color proofing is a contract between the customer and the printing house, which is a visual expression of the customer's product requirements and the printing house's commitment to quality. The effectiveness of using color proofing as a reference to control printing color has been proved by practice. It is an actual sample without verbal description and an effective communication tool to effectively convey color information from one person to another and actually carry it out.

 

In order to make a color proofing is practically available, it must match the printed product, the quality must be stable, color proofing is an important means of color communication in the printing industry.

 

Four, the main control parameters
In practice, you can see that good prints sometimes have a higher density, sometimes a lower density; Poor printing is usually dot increase is too large, dot increase is the direct cause of the paper to accept excessive ink, and dot increase is a result of the printing sheet appears too full or produce the wrong hue. Practice has concluded that there must be variables more important than field density.

 

With the popularity of four-color printing presses, densitometers have become widely used, but press operators have always had to visually conform to standard proofing. They adjust the press just as they would a color television set to achieve color balance on the sheet. This technique has attracted the attention of printing researchers as to why the printer's eye can outperform the densitometer. To answer the question, one must look at how a printer's operator works.

 

In order to obtain the desired printing effect, Rixiangde Moller adjusted the step reproduction of color separators by printing experiments with different densities of magenta and yellow field inks. The experiment found that matching color is more important than matching ink quantity. Because prints that reproduce well are produced with a small amount of ink, there is no benefit to printing with a high amount of ink.

 

Other studies have also indicated that print quality controllers pay more attention to color changes than to field density changes. It is more effective to combine the densitometer data with the visual evaluation of the printer to control the color of the printed image. It has also been found that the relationship between field density and hue change of mesh tone image is not so strong. In the printing process, the density of magenta can even be changed by 0.20 so much in order to obtain even and stable printing quality.

 

The famous printing expert Felix Brunal pointed out that the effect of dot increase on color reproduction can be much greater than that of field density. He believes that dot growth is a much more important control data than field density.

 

The Printing and Communication Association of America once conducted an experiment in which each of 16 web offset presses printed a set of test plates and printed an advertising image under the same printing conditions as the test plates. The printing conditions were supposed to be the same as the actual production conditions normally used, and the printers did not match the test plates with the proofs. The printing results were analyzed using color hexagonal shapes. The results showed that each operator produced similar overprinting colors through overprinting, dot enlargement and other printing parameters. This fact makes people believe that in order to get the correct hue and color saturation, the control of overprint mesh tone is the most important control objective.

 

Color matching is more important than ink volume matching in printing image reproduction, and color matching is more important than color saturation matching. This is the theoretical basis of the transition from density measurement and control to chroma measurement and control.

 

Five, densitometer in the application of color control

In order to produce a stable and consistent hue, the printer operator seems to compensate for changes in printing parameters by adjusting the inking. In the middle of printing, when the dot increases and changes, the overprint color will change significantly. The printer operator will maintain or reconstruct the matching relationship between the print and the standard proof by adjusting the amount of ink. The amount of ink printed to the sheet will affect the dot gain. Conversely, the dot gain can be controlled by changing the field density.

 

Automatic adjustment allows for better process control. The printing press is controlled by inking volume, and based on this premise, it is possible to quantify the expected mesh tone value (in the image, what the observer sees is hue and color saturation) and measure mesh tone density (rather than field density). As a result of the color combination, the observer sees the red, green, and blue violet light reflected from the printing sheet, which reaches the eye to form a synthetic color vision. Change dot increase and ink overprinting has a significant impact on the effect of printing color, the red, green, blue violet light of the formation of printing color can be displayed on the fluorescent screen and compared with the standard printing proof, so that it is possible to control the consistency of printing color.

 

Densitometers can effectively determine the reflectance of red, green and blue violet light on a given surface. So you can use a new densitometer to measure the color proofing or standard printing sheet on the specified mesh surface, the measured value as the surface printing control value or target value. When the printed matter passes through the printing press, the corresponding part of the printed matter is measured, and the measured value is compared with the target value, the automatic control of the printed matter quality can be realized.

 

The densitometer measures the density on the production sheet after the standard sheet is raised by zero, and then compares it with the density reading on the same part of the standard sheet. The measured value can indicate whether the yellow, magenta and cyan contents of the two are equal. If the value of the production sheet deviates from zero, this indicates that the printed image no longer matches the standard sheet and may have to be corrected. The three density reading numbers will indicate the necessary correction function. Densitometer reading will not indicate the change of printing conditions, but indicate the change of ink layer thickness, compensation for the change of printing conditions, will make the measurement surface back to the balance of red, green, blue purple color.

 

The production sheet may have the correct hue without the correct saturation, in which case all three density readings will be incorrect. Depending on the size and balance of the reading, necessary corrections can be indicated. Maintaining color balance is more important than maintaining correct color saturation.

 

What is not known at this point is the correct amount of acceptable hue and color saturation change. If these amounts are determined, algorithms can be determined, programmed and added to the system. Previous experience indicates that the densitometer is more accurate if it is adjusted to zero on paper rather than pre-proofing, which needs to be determined experimentally.