For copying of this type of manuscript, the density of the black and white field calibration standard should be larger, and the level curve of the medium and dark tone should be slightly reduced, and the level of the medium brightness tone including the subject tone should be reproduced more brightly. Make the reproduction of the picture clear, but also stressed the dark tone of the secondary differences, in order to achieve better tone contrast and visual brightness effect.
(6) Different manuscripts are distributed at the midtone level. Some manuscripts with medium-to-dense contrasts have fewer intermediate tone levels, a greater density difference, and high and low tone levels, such as color films shot against the light, should be designed to adjust the level of darkness of this type of image subject. Good copy reproduction effect can be achieved.
The level of image contrast can be used as a density range compression adjustment when copying. The height of the initial density can also be changed by setting the high optical density and adjusting the recording settings. However, whether the distribution of the original image hierarchy can meet the artistic requirements requires that the level distribution be compressed and the redistribution adjustment should be made. The depiction and analysis of manuscript level distribution is crucial to the redistribution adjustment of level reproduction and is the primary basis for level reproduction. When the printed matter is restored, the adjustment of the tone is generally required. When the density contrast of the original document is greater than the highest recording density of the printed matter, in order for the various tonality of the original document to be expressed in the printed matter, the tone must be restored. Appropriate adjustments. Second, in order to adapt to the reproduction requirements of certain special manuscripts (for example, photographs that are primarily highlighted, and photos that are primarily dark), some of the manuscripts must be properly emphasized, and other adjustments must be made. The main feature of linear compression is the adjustment of equal proportions of each tone segment. Linear compression does not represent true visually proportional compression because the D-Y curve is also nonlinear. After this compression, the luminance is adjusted to the human eye. It is not easy to identify and produce a "gray" phenomenon. The reproduction of tone refers to the relationship between the density of the original and the percentage of copying points. To make all the tone and color on the manuscript well represented in the printed matter, first select the correct level curve. The level is the basis of tone and color change. If the level is not rich on the screen, the color performance must be monotonous and boring, and only the realistic level can have vivid color changes.
The difference in the contrast range of the natural color film of the transmitted manuscript is relatively large (about 3.0 or so). Usually, the contrast is required to meet the requirements for the reproduction of the printed matter; while the manuscript of the reflected manuscript has less contrast, the manuscript is boring and can be based on different The original features are brightly copied. For example, the copy point of the portrait of a person is the color of the person's face, and the two colors M and Y are the key; the reproduction of the landscape picture is the natural scenery, and the two colors of C and Y are the main points. Flexible use of level knobs to adjust out a reasonable level of the curve, to correct the deficiencies of the original, to maintain the main part, the corresponding loss of the secondary part, boldly choose, try to make a good copy. However, if the adjustment of the level curve is unreasonable, it may result in the inversion of the primary and secondary images, the unclear level, and the inaccurate hue. Since color prints are to be reproduced as a picture with a consistent density range, this density range is mostly lower than the density range of color manuscripts. In the case of color separation and plate making, compression adjustment must be done. What kind of redistributive adjustments are taken at each tone level depends, on the one hand, on the distribution of the tonality levels of the manuscript, and at the same time it relates to human visual perception. Among them, both the Munsell brightness value of the visual response and the subjective factors of people's visual psychological requirements. To adjust and copy the original tonal hierarchies, it is necessary to sum up the people's visual psychological needs, add the physical values ​​of the visual response, and then consider the distribution of the original levels to obtain the density reproduction curve of the print screen. The evolutionary data in the process of copying and reproduction is designed to design a tone reproduction curve of a specific manuscript.
The density of printed matter is so large that it can not only reproduce the level of some manuscripts or original scenes, but also make it possible to open up some contrasts between levels and levels, and the sense of three-dimensionality is also strong. In particular, the subtle contrasts can be enhanced and the clarity of the image hierarchy can also be enhanced. On the other hand, it also makes the color of the picture open, which makes the deeper saturated, the shallower brighter, and enhances the three-dimensional color. However, the increase in the density of the printing ink layer is inconsistent with the dot gain, and it is impossible to achieve such a high density as a color transparency sheet. Only under the excellent conditions such as the adaptability of paper, ink, and equipment, and the precision of the printing press, can have lower dot gain value and higher ink layer density.
Therefore, the objective technical standard for determining this quality index is to use a color reflection densitometer to measure the printed solid density of each printing ink layer and the printing density of 75% dot, and calculate the printing K value. When having a higher printing K value (yellow plate 0.3 to 0.4, magenta plate and plate plate 0.4 to 0.55, and black plate plate 0.5 to 0.6), the density of each of them is high, and the superimposition efficiency of each ink layer is close to 90 At %, the tone of the print is better. Such printed matter must be clearly structured, full and full of three-dimensional images. In order to save printing ink, some people advocate reducing the density of the printing ink layer to reduce the dot gain. In this way, although the number of printed dot adjustments is reduced, the leveling of the dark tone end of the image is reduced, but the overall tone contrast is not the highest. , also can not reach the best level of print tone reproduction.
As the printing process tone is non-linear, compensation adjustments should be made before printing. The network tone adjustment is limited by various conditions during the process of printing and printing, and the transmission of the tone network is non-linear. In order to adapt to the printing process, compensation adjustments must be made. The key point is to make adjustments to the three outlets of the printing area, which are also called three key areas, namely 3%, 50%, and 80% outlets. Because 3% small points are easy to lose, it will affect the color level of the highlight area, 50% of the dot area will easily increase, affecting the midtones, changes in the color of the special characters, 80% of the dot area will be easy to merge, affecting the tone level, especially It is the dark color of the main color and the deep color of the same level, so that it is difficult to balance the two, often at a loss. Therefore, for some important colors and important parts of manuscripts, they are adjusted so as to avoid these three dot skip areas, thereby providing an ideal printing plate for printing, making it printable, and printing a good product.
Manuscript resolution problem
The clarity of color prints is an important quality indicator for image reproduction. Except for the special artistic conception of imagery, at least part of the hierarchy (main body or background) of each image is clear. The requirements for sharpness mainly include the following aspects.
(1) The solidity of the image level outline. First, it is necessary to base the factual (ie, sharpness) of the boundaries of the manuscript hierarchy. At the same time, it also depends on the size of the aberrations of the plate-making optics, the thickness of the electronic color separation analysis and the recorded scanning spot, and the accuracy of the four-color image fit. In the whole process of copying and reproduction, the transition width of the image level boundary is gradually widened, especially enlarged copying. The level boundary reality cannot be restored. The sharpness of the borders of the print hierarchy just seems to be emphasized by the separation of the colors.
(2) The clarity of contrast changes in the two adjacent levels of the image, namely the fine contrast. If the density of the adjacent levels differs greatly, the visual perception is clear. On the other hand, if the density difference is small, the level is flat and the vision is not easily discernible. The subtle contrasts are mainly determined by the secondary differences of the manuscript layer, and are also constrained by the duplication and compression of the tone levels and the distribution of the level adjustments. In the separation of color separations, the emphasis of the level boundary can be emphasized, and the visual contrast of the boundary of the level can be increased. The subtle levels of contrast can be substantially enhanced.
(3) The resolution of the manuscript or the print screen hierarchy, that is, the subtle degree of its subtlety, is the essence of the composition of the objective scenery objects, that is, the so-called texture. Prints are based on the fine resolution of the original image, but are compromised by the resolution of the plate-making optics, the magnification, the thickness of the screen, and the influence of the four-color version. After the plate printing process, the fineness of the original layer cannot be restored. In color separation and platemaking, measures such as false light masks and electronic effects should be adopted to add “trimmings†to the borders of the image levels, so as to emphasize the visual clarity of image layer duplication. The “trimmings†added to the boundaries of the copied image hierarchy include two visual effects produced by the width and height of the peak. The height of the peak positive and negative densities is non-linearly transmitted to vision, and only enhances the visual Mach band effect, but it is not easily visually decomposed. The size of the “trim†width is linear to the vision, and is too large (especially at the bright side of the border) to be visually discerned, giving rise to a stiff embossed sense; being too small is not conducive to producing a visual Mach band effect. Only with the appropriate combination of the width and peak height of the "trimming" can we produce visual Mach tapes that are clearly and unresolved, and at the same time enhance the visual illusion of subtle contrast and subtle levels of resolution.
Therefore, the objective technical standard for determining this quality index is to use a color reflection densitometer to measure the printed solid density of each printing ink layer and the printing density of 75% dot, and calculate the printing K value. When having a higher printing K value (yellow plate 0.3 to 0.4, magenta plate and plate plate 0.4 to 0.55, and black plate plate 0.5 to 0.6), the density of each of them is high, and the superimposition efficiency of each ink layer is close to 90 At %, the tone of the print is better. Such printed matter must be clearly structured, full and full of three-dimensional images. In order to save printing ink, some people advocate reducing the density of the printing ink layer to reduce the dot gain. In this way, although the number of printed dot adjustments is reduced, the leveling of the dark tone end of the image is reduced, but the overall tone contrast is not the highest. , also can not reach the best level of print tone reproduction.
As the printing process tone is non-linear, compensation adjustments should be made before printing. The network tone adjustment is limited by various conditions during the process of printing and printing, and the transmission of the tone network is non-linear. In order to adapt to the printing process, compensation adjustments must be made. The key point is to make adjustments to the three outlets of the printing area, which are also called three key areas, namely 3%, 50%, and 80% outlets. Because 3% small points are easy to lose, it will affect the color level of the highlight area, 50% of the dot area will easily increase, affecting the midtones, changes in the color of the special characters, 80% of the dot area will be easy to merge, affecting the tone level, especially It is the dark color of the main color and the deep color of the same level, so that it is difficult to balance the two, often at a loss. Therefore, the important colors and important parts of some manuscripts are adjusted so as to avoid these three dot jump zones, so that an ideal plate is provided for printing, so that it can be printed well and a good product can be printed.
Manuscript resolution problem
The clarity of color prints is an important quality indicator for image reproduction. Except for the special artistic conception of imagery, at least part of the hierarchy (main body or background) of each image is clear. The requirements for sharpness mainly include the following aspects.
(1) The solidity of the image level outline. First, it is necessary to base the factual (ie, sharpness) of the boundaries of the manuscript hierarchy. At the same time, it also depends on the size of the aberrations of the plate-making optics, the thickness of the electronic color separation analysis and the recorded scanning spot, and the accuracy of the four-color image fit. In the whole process of copying and reproduction, the transition width of the image level boundary is gradually widened, especially enlarged copying. The level boundary reality cannot be restored. The sharpness of the borders of the print hierarchy just seems to be emphasized by the separation of the colors.
(2) The clarity of contrast changes in the two adjacent levels of the image, namely the fine contrast. If the density of the adjacent levels differs greatly, the visual perception is clear. On the other hand, if the density difference is small, the level is flat and the vision is not easily discernible. The subtle contrasts are mainly determined by the secondary differences of the manuscript layer, and are also constrained by the duplication and compression of the tone levels and the distribution of the level adjustments. In the separation of color separations, the emphasis of the level boundary can be emphasized, and the visual contrast of the boundary of the level can be increased. The subtle levels of contrast can be substantially enhanced.
(3) The resolution of the manuscript or the print screen hierarchy, that is, the subtle degree of its subtlety, is the essence of the composition of the objective scenery objects, that is, the so-called texture. Prints are based on the fine resolution of the original image, but are compromised by the resolution of the plate-making optics, the magnification, the thickness of the screen, and the influence of the four-color version. After the plate printing process, the fineness of the original layer cannot be restored. In color separation and platemaking, measures such as false light masks and electronic effects should be adopted to add “trimmings†to the borders of the image levels, so as to emphasize the visual clarity of image layer duplication. The “trimmings†added to the boundaries of the copied image hierarchy include two visual effects produced by the width and height of the peak. The height of the peak positive and negative densities is non-linearly transmitted to vision, and only enhances the visual Mach band effect, but it is not easily visually decomposed. The size of the “trim†width is linear to the vision, and is too large (especially at the bright side of the border) to be visually discerned, giving rise to a stiff embossed sense; being too small is not conducive to producing a visual Mach band effect. Only with the appropriate combination of the width and peak height of the "trimming" can we produce visual Mach tapes that are clearly and unresolved, and at the same time enhance the visual illusion of subtle contrast and subtle levels of resolution.