Cosmetic Boxes Of Magnetic field Grey balance and dot expansion principle (2)

Cosmetic Boxes Of Magnetic field Grey balance and dot expansion principle (2)

Third, network expansion and network expansion curve

 

(1) Network expansion

Dot expansion is a kind of dot size change phenomenon in the process of plate making and printing, which makes the actual dot area greater than the expected dot area.

 

(2) Types of network expansion

According to the process of dot expansion phenomenon can be divided into two categories, they are the dot expansion in the plate making process and the dot expansion in the printing process.

 

1. Plate making stage of the network expansion

In the process of plate making, the dot expansion mainly exists in the two processes of film output and printing. The main factor affecting the dot expansion of film output is the nonlinear effect on the phototypesetter optics, which can be solved by the calibration of the phototypesetter, commonly known as the linearization of the phototypesetter. There are more factors affecting the dot expansion in the printing process, which can only be compensated by controlling the process parameters. This kind of dot expansion can not be reflected in the setting of color separation parameters, and the dot expansion generated in the printing process should be considered when setting color separation parameters.

 

2. The printing process network expansion

Dot expansion is an inevitable phenomenon in the printing process, and its impact on the quality of printed matter is crucial. Under the action of printing pressure, the ink will expand around the dot. At the same time, due to the compression deformation of the lining, resulting in the relative slip between the plate and the paper (or the plate and the rubber blanket), the rubber market and the paper, this slip will also cause the expansion of the dot. Obviously, network expansion due to expansion and slippage is always unavoidable.

 

In addition, the paper's double reflection of light can also cause the expansion of the dot. When white light shines on white paper, about 80% of white light is reflected, but only 10% of white light is reflected when white light shines on the dot covered with ink and the intersection of white paper. In this way, the human eye adds a circle of ink around the real dot when viewing the dot. Although the network has not actually changed, the perceived message is that the network has expanded.

 

(3) The network of different output devices is expanded

The development of computer peripheral equipment technology has brought the diversification of output equipment, and also makes the output of images can have a variety of choices. Different types of output devices have different dot expansion rules, even the same device may produce different dot expansion. For example, the dot expansion value of the black and white laser printer is much higher than that of the offset press, the dot expansion value of the intermediate adjustment is usually about 35%, and the dot expansion of the inkjet printer is lower.

 

Therefore, the control of dot expansion is not only meaningful for printing on the press, it is also important for output to the printer. Although the general printer is not a Post Script printer, they do not recognize the color separation setting parameters, but trying to control their dot expansion value is very important to obtain accurate image output.

 

Control of dot expansion on non-Post Script laser printers or other printers cannot be achieved through color separation Settings, but can be adjusted with certain color adjustment commands, such as Brightness/Contrast command to make the image brighter so that the printed image does not appear dark.

 

(4) The intermediate adjustment dot expansion value of different ink paper combinations

Each Ink Colors combination in the Ink Colors list has a specific set of intermediate dot expansion parameters. This set of parameters is Adobe's estimate of the intermediate dot expansion value of each color plate under different ink paper combinations, and it is derived from the practical experience of many printing companies for each ink paper combination. For users without professional knowledge, these parameters not only play a guiding role, in most cases can get good color separation results.

 

For the convenience of the reader, the following table lists the estimated mid-tone dot expansion for all ink and paper combination color plates built into Photoshop.

 

Table different ink paper combination color plate intermediate adjustment dot expansion default value ④ coated paper (coated paper) dot expansion value is less than offset paper.

The following rules can be summarized from the tabular data:

① All ink and newsprint combinations use the same dot expansion value, and the dot expansion value is the largest;

 

(2) Among the four color plates, the dot expansion value of the green plate is the largest, and the dot expansion value of the other three color plates is the same;

 

(3) The difference between the dot expansion value of the newspaper printing medium blue plate and the dot expansion value of other color plates is 3%, and the dot expansion difference between the green plate and the other three color plates of other ink paper combinations is 4%;

 

(4) Standard network expansion curve

Photoshop has a set of default dot spread values for the Ink and paper combinations listed in the Ink Colors list. Each ink and paper combination has an estimate of the dot spread in the middle of the color plate. The software uses this value to build the dot spread curve of the color plate and adjust the dot spread of the entire image. Such dot expansion curves are called standard dot expansion curves, and they are provided by software.