Data Quality Gray Balance Control Rule II for Printing Quality

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 Plate Ink Rs: Reflection Density 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.

(to be continued)