Research on Printing Grey Balance Control Rule

Summary

The improvement of printing quality requires the establishment of data concepts so that the stability of the reproduction can be controlled. Gray balance measurement is often used to determine whether the replica is an important basis for color cast, so the gray balance of data will be able to improve the quality and stability of print. The data-based gray balance control law is the subject of this study.

Preface

Gray balance is an important basis for judging copying when making color copies. After the color reproduction is measured by a concentration meter, the ink amounts of the three primary colors are overprinted to achieve neutral gray. Neutral gray produces a color cast that is easily noticeable because people are particularly sensitive to gray. When the original is reproduced, his neutral color is the same as the neutral color of the replica, then the hue balance of the color reproduction can be considered correct. Therefore, the color copying staff regards the gray portion as the basis for the color cast and the reference for printing quality.

Since the yellow, magenta, and cyan inks contain noises other than themselves, they cannot be overprinted with the same concentration to get the concentration you want. Therefore, in order to make the prints not be color cast, it is necessary to find the appropriate concentration of the three primary colors of the overprint to achieve the gray balance. In the process of color reproduction, the main control of gray balance is to control the area size of the dots of the three primary colors, rather than the thickness of the ink. The grey color printed by the three primary colors of different sizes is used to determine whether or not the grey color is balanced. The concentration is measured in gray color patches. When the values ​​of clear, magenta, and yellow are the same, the gray balance has been reached.

Because there are many different inks in a printing plant, the dot sizes of the three primary colors combined by different inks may be different, not to mention the errors in different environments or different requirements and conditions. The factors that affect the gray balance include ink volume, paper, dot area,,,,,, and so on, and the balance value needs to be applied to the CIE uniform color space and the color difference formula. Therefore, this paper hopes to sort out some methods for obtaining gray equilibrium concentration values, describe these methods in detail, compare the advantages and disadvantages of these methods, and the applicable environment, and then obtain the rules of the gray balance control method.

è´°, theoretical basis

The theoretical basis is mainly to facilitate readers to understand the text, so it is divided into two points, one is noun explanation second, CIE uniform color space and color difference formula

I. Glossary

(A). Gray Balance (Gray Balance)

After the color reproduction is measured by a concentration meter, the ink amounts of the three primary colors are overprinted to achieve neutral gray. In general printing will add a black version to increase the dark part of the hierarchy.

(B). Chroma

The color has a neutral color component, the higher the value, the farther away from the neutral color; the lower the value, the closer to the neutral color.

(C). Colorimetry

It is a comprehensive science that involves the cross-disciplinary fields of physical optics, visual physiology, visual psychology, psychophysics, etc., based on the science of human visual perception to measure color.

(d).CIE Color System (CIE International Commission on Illumination Commission International del` Eclairage)

The stimuli of color and the sense of color are the source, the attenuator, and the detector. These three elements form the basic structure of the CIE color system.

(e). CIE Standard Illuminants

Defined from the standpoint of spectral energy distribution, it may not be able to be made into a physical light source for human visual and color measurement.

(VI). CIE Standard Light Sources

The CIE standard illuminant was calibrated by a body made of CIE Standard Illuminator to simulate its relative spectral energy.

Second, CIE uniform color space and color difference formula:

(a). CIELAB color space:

CIE used the 1976 L*a*b* color space, abbreviated as CIELAB.

a*: Red and green coordinates, with red at timing and green at negative.

b*: stands for yellow and blue coordinates, yellow for timing, and blue for negative.

L*: the brightness value, 0 is the ideal black, and 10 is the ideal white.

(b).CIELUV color space:

CIE recommends the second uniform color space, "CIE 1976 L*u*v* color space" referred to as CIELUV. u*: Red and green coordinates, with red at timing and green at negative.

v*: yellow-blue coordinates, yellow on timing, and blue on negative.

L*: lightness.

(c).CIELCH color space

Other representations from CIELAB and CIELUV are called CIELCH (L* C* h°)

C*: color

h°: the hue angle representing the hue

(D). CIELAB color difference formula:

(e). CIELUV color difference formula:

叁, factors that affect the gray balance

One. Ink volume:

The yellow, magenta, and cyan inks contain noises other than themselves, so you cannot overprint the inks with the same density to get the concentration you want. This is the ink's impurity characteristics. The change in the amount of ink will affect the density of the outlets, so the amount of ink on the layout needs to be managed, and the method of managing the amount of ink is managed by printing the full-page density.

2. Paper:

Due to the difference in surface texture of the printed material, the percentage of dots on the printed material will change, and the dots will usually expand. As light passes through the paper, it is affected by four factors:

(A) absorption of ink layers (inks of ink layers)

(B). First surface reflectance

(c). Paper reflectance

(d). Multiple internal reflectance

Three. Solid Ink Density-SID:

The so-called full plate density refers to "the highest concentration of paper coloring material." That is, R, G, B three color filters to measure the highest concentration of C, M, Y ink. When the full-plate density exceeds a range, the dot gain is more severe and the print contrast is lower. It will lead to a reduction of the screen level, which will make the screen lack a three-dimensional effect.

Ds=-logRs Rs=10-Ds

Ds: full plate density

Dr: Reflectance of full-print ink

Rs: reflection concentration

Dr=-log(R)

When printing, we need to control the full plate density. During the printing process, if the full plate density of CMYK is not set, one of the four colors will produce a difference in the concentration, which will result in an error in the finished product. The printing factory set a fixed set of four full-color full-plate concentrations, which can effectively control the gray balance.

4. Dot Area-DA

(I). Film Dot Area-FDA

FDA=1-Tt Tt: Plane Film Transmission Dt: Plane Film Integration Concentration

(B). Effective Dot Area (EDA)

EDA=FDA+(ODG+PDG)

ODG = Optical Dot Gain

PDG = Mechanical Dot Gain

(C). Practical Dot Area-PDA

PDA=FDA+PDG

In color separation, the appropriate three-color dot area is determined, and the appropriate dot area on the overprint varies depending on the printing conditions. Ps: Euler's equation a=PDA, Murray’s equation a=EDA

V. Overprint:

In the subtractive method, the three primary colors of yellow, magenta, and cyan in the three-color overprinted gray portion cannot correspond to the original, and the dark portion lacks contrast. The black ink in the four-color overprint can make the three-color overprint increase the dark portion concentration, and can also be used as the gray. Departmental replacement (GCR) approach reduces costs and makes it easier to achieve a grey balance. However, the addition of the black version will reduce the contrast, so we should consider whether to use it according to different needs.

According to the needs of different reproductions, the use of the black version can be divided into three types:

(a) The first type of black plate is used to extend the maximum concentration of replicas due to the insufficient concentration of overprinting of the three primary color inks.

(B) The first type of black version of the extension, but increase the role of UCR, so that the three primary colors of ink will only reach a certain level; and increase the black version of the amount of ink to replace the overprint part of the three primary colors of ink.

(3) The full-grade number blackboard can be divided into two forms, the difference being that both use UCR.

6. Screen Ruling

The number of screen points within the length of a printed product, the greater the number of screen lines, the finer the performance of the printed matter; the smaller the number of screen lines, the reverse is true. Screens can be divided into glass screens, contact screens, and word network screens. Instead, contact screens are the mainstream. The shape of the contact screen is further divided into a chain type network point and a square type network point.

Different replicas have different requirements, so there are different screen lines, which can usually be divided into lines of 65.100.120.150.175.200.300 (lines/inch). The quality of printing is not that the larger the number of screen lines, the better, because the more detailed the number of screen lines, the more serious the dot expansion. Therefore, Zhang Haozhao's master's thesis “Study on Screen Balance in Gray Balance” discusses the neutral balance of different screen lines in gray balance.

Candle Box

Cardboard Candle Box, Candle Boxes, Candle Packaging

Rigid Paper Box,Cosmetic Box,Perfume Box Co., Ltd. , http://www.rigidpaperboxes.com

Posted on