Basic elements and analysis of the hottest color s

  • Detail

Basic elements and analysis of color code (I)

applied terminology field density in the process of printing process control and image reproduction control, field density is the most important characteristic that needs to be measured. It represents the saturation of the largest real color block that can be obtained in the process of printing copy. However, since the size of the field density in any specific printing process is related to the thickness of the ink layer, this feature also controls other parts of the copy process, including non field areas. In addition to controlling the saturation level of the main color and overprint field and the dark part, the balance between the main color field density determines the hue after overprint. (the density of Rehmannia glutinosa and field green determines and controls the hue of the generated green). Other printing characteristics, such as dot enlargement, printing contrast, color difference, also depend on the field density to determine whether they represent normal or abnormal printing conditions. For example, when the density value is greater than or equal to the value on the color scale, a larger dot spread is normal and controllable; On the contrary, if the dot enlargement is higher than the normal value when printing with a lower density than the requirements, it indicates that there is an abnormal situation. At this time, even if the image looks acceptable, action should still be taken to solve the problem. Other independent printing variables, such as plate exposure, packaging grade, drum setting, also play an important role in image tone and color control. Field density is the only variable that the printing operator can adjust during the operation of the printing machine. Printing contrast printing contrast is the measured value after comparing the field density in the printed matter with the density of 75% of the gradient of a certain color. It is a very useful printing characteristic because: · it marks the reproduction status of the image on the gradient curve· Although printing buyers do not realize that they use vision to evaluate the printing contrast, in fact, they usually use this property as the evaluation of the quality of printed products. Printing with high contrast usually gives people a feeling of jumping, mainly because the dark tone area with high saturation and the relatively extended three-quarters tone area have three-dimensional characteristics, as if they want to stand out from the paper· The printing contrast data itself provides rich process information, including: 1) ink density, 2) the point expansion value in the more important three-quarters tone area, and 3) the ability to improve the ink density without slightly expanding the replication of the three-quarters tone area. If the printing contrast value is too large, it indicates that the density of the field ink increases, but the density of the corresponding three quarter tone block does not increase with it. (the increase of three-quarters tone density may be caused by dot enlargement, paste, dirt or other factors), so that the visual contrast between the field and the three-quarters tone area increases. Similarly, the decrease of printing contrast shows that: 1) with the increase of field ink density, the three-quarters tone area is gradually filled, making the image hierarchy smooth and reducing the contrast between the dark tone and the three-quarters area. 2) The printing operator deliberately reduces the ink density in the field to extend the tone of the important three-quarters of the area, flatten the image reproduction, and reduce the contrast between the dark tone and the three-quarters of the area. Gray balance gray balance refers to the combination of halftone dots of cyan, magenta and yellow to form a neutral gray tone for a specific printer, paper and ink combination. It is very important to understand the gray balance of the printer paper ink combination, which reminds color separation and printers to pay attention to correcting the color in the process of color separation. The gray balance color scale is particularly important for printer operators and managers, because if these three colors produce red, blue, or yellow, or are somewhat heavier or lighter than ink with the same visual chromaticity density value, if the increased length of the gray level is conducive to better transfer the stress from the polymer to the stronger fiber reinforcement, and the color block has some color deviation, such as red, blue, or yellow, it can be measured, Trace the root of this adverse change. Although the grey balance is different for each printing machine, and different for each roll of paper and each batch of ink produced, the investigation and experience show that the values summarized in the whole market are still available. Table 1 lists the proportion of various colors of inks that may be obtained in the market when gray balance is reached. Table 1 visual gray balance percentage 25% 50% 75% green 25% 50% 75% magenta 16% 39% 63% yellow 16% 39% 63% the gray balance value in the table is the recommended value, not a standard or specification. At the same time, it should be noted that each color separation personnel will use different data. Although in theory, people may think that the use amount of the three inks should be the same when copying neutral gray, in fact, it is not the case. The printing primary color pigment is not as pure as in theory, and it will reflect back some light that should have passed through. It is necessary and useful to briefly explain the theory and the real world: theoretically, hypothesis 1) printed matter should be detected under white light composed of equal energy red, blue and green light; 2) The paper is ideal white. Ideal cyan ink can absorb all red light and transmit all blue and green light; Ideal color ink can absorb all green light and transmit all blue and red light; Ideal yellow ink can absorb all blue light and transmit all green and red light. The ideal paper can reflect 100% of the color light passing through the ink. In fact, paper and pigments with these ideal characteristics do not really exist. Due to the impure mixture of pigments, the inks we use are like contaminated pigments. Specifically, cyan ink seems to be mixed with some magenta ink and a little bit of cyan ink, and yellow ink seems to be mixed with some magenta ink and a little bit of cyan ink. The fact that each color in tricolor ink is polluted by the other two colors is also the factor that produces the ink gray balance color deviation. As a result, the color separation personnel must adjust the dot size to produce neutral gray during overprint, and the same dot size printed with three kinds of color inks will produce brownish color. Similarly, since there is no ideal paper, the paper itself becomes a color filter, and the light passing through the transparent ink cannot be 100% reflected back. The surface view area and the surface view expanded surface view area refer to the values of the halftone dots that have been printed. For example, if we print 50% of the intermediate tone into 72% of the hue, we can say that the surface area of the printed film color code is 72%. The surface area value is the ratio of the hue value of a certain hue to the actual hue value. View expansion, also known as general view expansion, refers to the perceptible expansion (or total increase) of tone. For the above example, 50% of the views in the table are expanded to 22%. Dot enlargement: · it is not a printing defect, its occurrence is normal and predictable, and it will not affect the printing quality as long as the following conditions are met: 1) the predictability and correctability of halftone dots in the process of color separation, 2) measurement and control in the process of film making, proofing and printing· It is divided into two parts: mechanical point expansion, which refers to the physical increase of each half step adjustment point region; And optical point enlargement, which refers to the change in the appearance of half tone points obtained by the human eye (under normal observation distance and typical observation conditions) or densitometer. Some studies of GCA and other organizations have shown that mechanical dot expansion is affected by many factors, including film copying, plate making, printing and packaging, paper surface characteristics, ink properties, and so on. Each of these printing processes may change the size and shape of the top half of the final print. The choice of positive or negative printing plates also has an impact. The way these plates are exposed increases the actual size of the middle tone of the negative plate by about 2%, and sharpens the middle tone of the positive plate by about 2%. On the other hand, the expansion of optical dots is most affected by the type of paper. The optical absorption, moisture absorption and smoothness of paper are the dominant factors that affect the human eye (or densitometer) to observe the printed halftone dots. The absorption of ink by paper leads to larger mechanical point size, and the absorption of light by paper leads to larger mechanical point size. The absorption of light by paper leads to an increase in the size of optical points. The smoothness of the paper will affect the degree of view increase, because the rough paper has an uneven surface compared with the coated paper after amplification. And there are also differences between coated paper. High quality No.1 coated paper is smoother than No.5 coated wood pulp paper. Since the light shines on the surface of the printing paper, hits individual fibers and coated particles, and scatters on the paper surface, the smoothness of the paper surface will affect the expansion of optical points. The coarser the paper is, the stronger the scattering is. In the process of light reflection, part of the light is absorbed by the ink due to the influence of the half tone point, which makes the point darker, just like the half tone point has been expanded. When discussing the point expansion: · the general view expansion including mechanical and optical components should be considered. When the customer checks the printed matter or sample, what he observes is the expansion of the overall view. At this point, the influence of mechanical and optical factors on the total number is not different, but it is particularly important for the operator. Although the large-scale exploitation and supply of vanadium resources can be estimated by measuring and observing the color code, and the mechanical point expansion can be realized, there is actually no accurate method to distinguish optical and institutional point expansion; Observe this part through the manual synchronous data display screen of the subjective manual control box (handheld control system), the force value of the current sensor and the position of the beam during the test, the high-end configuration of the return button, the return button, the stop positioning control, the sample clamping control, the clear mark, and the color code elements that are easy to control· Although the point enlargement can be calculated according to different chromaticity values, the general view enlargement usually refers to the point enlargement value of 50% of the intermediate tone, for example, in the samples of specifications for web offset publications (swop). Blur/double shadow blur/double shadow is a common printing fault, which is caused by the slight movement or secondary contact between the roller and the paper. More accurately, double shadow is a secondary image generated by the slight poor registration of the image on the blanket when it is transferred to the paper surface. Sometimes, like the leather cloth, only part of the image is transferred to the paper, and the rest is printed on the paper inaccurately. At this time, double shadows are generated. After inspection, double shadows will produce additional images that are not oriented. The paper is not smooth and the rubber part is stretched. Sometimes the paper is patted on the rubber part, causing the paper to contact the leather cloth twice, which is the main reason for the double shadow. When half tone points are ghosted, each point will have a slight shadow, which increases the mechanical (and optical) appearance of the point. Blur refers to the slight sliding of paper or blanket, which causes the image to produce a blurred image during the printing process. This phenomenon will occur if the blanket is not firm. After testing, blur will produce an additional image of orientation, that is, the point will stretch in only one direction. Blurring makes the halftone dots oval, which changes only in the direction of the manufacturer's stretching experiment on the hair, and also increases the size of mechanical and optical dots. When there is no double shadow and blurring, it will also produce dot expansion, but blurring and double shadow are the causes of the expansion of the general view

Copyright © 2011 JIN SHI