The traditional printing quality control methods can not make the printing effect of newsprint catch up with coated paper. The main reason is that the quality of newsprint paper is poor, and the quality of coated paper is good, resulting in different density on the spot when printing. The contrast of coated paper can reach 1.7, while the newsprint is only about 1.4. Conventional printing control, which usually controls the density in the field, reduces the value of the density in the field, and all other parts also decrease linearly. Newsprint printing is the same as the linear compression of coated paper. If the HR is set as a constant, it actually plays a selective compression effect on the news printing, that is to keep the bright tone, compression dark tone, G7 is to do so. In commercial printing, regardless of any substrate, the G7's requirement is: In the gray tone at the middle, ie 50% C, 40% M, 40% Y, the relative density value is 0.54, and the chroma is 0~2. Because the density and color of the intermediate tone are guaranteed, the density change in the bright tone is guaranteed, and only the dull tone of the human eye is unresponsive, thus achieving the “identity†printing of different printing materials. Under the premise of guaranteeing the maximum density, the density at 50%C, 40%H, 40%Y is guaranteed to be a fixed value of 0.54 when printed on all papers. Since dark tone is not the focus of copying, the relative K value of print contrast, which reflects changes in shadow tone, is not a measure.
Where is the G7's control point HRA? It is not difficult to see from the relationship between density and the brightness of Munsell that the HRA with a density of 0.54 is almost at the sixth level of Munseen.
It is not difficult to observe from the above graph that the curve segment with the largest slope is at the 10th to 6th level of the Munsell brightness value, that is, the density value is at O~0.54. Therefore, this HR point represents a turning point in human visual observation. From this point to the left, the human eye feels stronger, showing a very short curve that corresponds to a 4-level lightness perception; and to the right, the observational power becomes sluggish, showing a very long curve that corresponds to a 6-level lightness perception. Therefore, the density segment of 0~0.54 is the part of the image that we need to protect in the printing. The highlight range is measured separately and it can be quickly checked in the middle during printing or after printing. In G7, it replaces TVI and checks overall darkness and gray balance. HR has two data: one for the gray balance of CMY, the other for monochrome black. Three-color gray HR, its three-color combination (50C, 40M, 40Y), monochrome black HR, the dot percentage of 50K, their relative density values ​​were 0.54 and 0.50. The bright-ranging range HR is also the core control part of the G7 control process and is the parameter most needed for control in a large number of experimental studies.
Where is the G7's control point HRA? It is not difficult to see from the relationship between density and the brightness of Munsell that the HRA with a density of 0.54 is almost at the sixth level of Munseen.
It is not difficult to observe from the above graph that the curve segment with the largest slope is at the 10th to 6th level of the Munsell brightness value, that is, the density value is at O~0.54. Therefore, this HR point represents a turning point in human visual observation. From this point to the left, the human eye feels stronger, showing a very short curve that corresponds to a 4-level lightness perception; and to the right, the observational power becomes sluggish, showing a very long curve that corresponds to a 6-level lightness perception. Therefore, the density segment of 0~0.54 is the part of the image that we need to protect in the printing. The highlight range is measured separately and it can be quickly checked in the middle during printing or after printing. In G7, it replaces TVI and checks overall darkness and gray balance. HR has two data: one for the gray balance of CMY, the other for monochrome black. Three-color gray HR, its three-color combination (50C, 40M, 40Y), monochrome black HR, the dot percentage of 50K, their relative density values ​​were 0.54 and 0.50. The bright-ranging range HR is also the core control part of the G7 control process and is the parameter most needed for control in a large number of experimental studies.
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