Technical essentials of printing image design for

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Technical points of packaging and decoration printing image design II

II. Treatment of insufficient originals

1 The processing method of color deviation

the true state of different original colors can be observed intuitively from the measurement of the contrast of the original three color density and the description of the three color density curve. The most popular density range division method in color printing reproduction technology, which divides the entire density range of originals and reproductions into four segments. 2 When the relief point exceeds the actual Rp0.2, that is, the entire density range between the highlight point (white field) and the dim point (black field) is divided into three segments: bright tone (also known as high tone), intermediate tone and dark tone, and the area less than the density of the highlight point is called extreme highlight. Some also divide the density range into five segments, that is, in addition to the above four segments, the area with higher density than the dark tone is called extremely dark. In the analysis of the color quality of the original, if the trichromatic density and contrast of the original are basically the same, it means that the original is not biased and the tone is basically normal. If the gradation is complete, the level is rich, and the distribution is reasonable, even if the total contrast is slightly different, it can be regarded as a normal manuscript. Its color reproduction can be corrected according to the normal color error. The development of the next 10-20 years depends on the improvement of the enterprise's independent innovation ability. The poor data will be corrected, and the emphasis will be on the step level reproduction. If the trichromatic density of the original is different, it indicates that it is biased to a certain color. When the contrast of the trichromatic density is basically equal, it is a balanced color bias, which is caused by color fog. Generally, this kind of color deviation manuscript has a good gradation level. You can change the setting of high-key and low-key trichromatic point records of the color separation picture, and cooperate with the adjustment of middle note gradation to achieve the full gradation gray balance to eliminate the image color deviation. However, it is best to design a hierarchical reproduction curve to adjust the balance of three colors and gray according to the three color density curve, which can make the tone of full tone be uniformly corrected. If there is a large difference in the three color density of the highlight of the original, the three color density at the dark end is close to the same, and the color deviation is mainly manifested in the high-key area, which is detrimental to the high-key level reproduction of the image. Although this kind of color deviation can be directly and simply used as the white field balance and input of the color separation machine with the original color deviation highlight, Jinan new era gold assay instrument Co., Ltd. has summarized some common sense calibration of a lot of experimental machine safety protection, and changed the input balance of the color separation machine, the color calibration signal has also changed, the highlight color that should be retained has also been lost, and the data

is often inaccurate. It is best to deduce and design the hierarchical reproduction curve of the trichromatic plate according to the trichromatic density curve, change the recording setting of the highlight trichromatic points of the color separation picture, and accurately correct the high-profile color deviation. If the highlight trichromatic density of the original is basically the same, only the trichromatic density at the dark end is different, and the density contrast is also different, showing obvious color deviation in medium to dark tones. The dark tone level is slightly lost, and the medium and high tone level is normal. You can change the setting of the dark tone three color dot recording of the color separation picture, or add the full tone bottom color removal of a color (only effective for mixed multicolor), so as to eliminate the color deviation of the three color recording picture at the dark tone end. It is better to deduce and design a trichromatic hierarchical replication curve to adjust the gray balance from the trichromatic density curve, which can correct its color deviation according to accurate data. If the three color density curve of the original is crossed, the high-profile image is biased to one color, and the dark end is biased to another color, which is caused by the imbalance of the three colors of the photosensitive film itself. Its gradation levels are bad at all levels, so it is not easy to correct its color deviation directly by changing the adjustment and recording settings of the three-color hierarchy on the scanner or color splitter. We must deduce and design an accurate adjustment gray balance three-color hierarchy replication curve according to its three-color density curve, and guide its three-color hierarchy adjustment and recording settings, so as to slightly improve its replication effect. If the color deviation density difference is more than 0.2, it is generally difficult to correct replication. When encountering a biased manuscript with serious color deviation and large trichromatic density difference, in addition to measuring its high light and dark trichromatic density meal, it is best to measure the trichromatic density of neutral gray in the middle of the original scene. This kind of manuscript needs to be based on the trichromatic density curve, deduce and design an accurate adjustment gray balance trichromatic level replication curve, and then carry out color deviation adjustment on the desktop system and color splitter. However, when dealing with the original color deviation, we should pay attention to carefully analyze whether the picture is really color deviation, because some of them are artistic effects created by the author intentionally. For example, backlight photos, because backlight works pay attention to the use of light, and the hue changes greatly, can form a variety of different color tones. Some are mainly warm colors, and some are mainly cold colors. However, it should be taken into account that the tone of some backlight photos seems to be somewhat biased, which is actually the author's deliberate pursuit. Therefore, this kind of manuscript cannot be considered as biased, so when copying, we should carefully analyze the manuscript, fully understand the author's creative intention, and accurately grasp the tone of the picture. For originals with obvious color deviation, not only the measurement of trichromatic density data is required to be very accurate, but also the correction of color deviation should be considered first when color separation reproduction is carried out. The hierarchical reproduction of its trichromatic plate should not only adjust the trichromatic balance of the original tone, but also make redistribution adjustment of its hierarchy, which should be the focus of operation. Its color reproduction 4.2.2 the correction of the error of the scanning rate calculation formula should be carried out on the basis of the data that the tricolor plate is adjusted to the printing gray balance. Due to the change of the color signal of the color deviation manuscript, the color correction data will also change, which needs to be based on the image color and chromatographic color combination data after the color deviation is eliminated by the compensation color chip, and finally correct the color error

2. The processing method of hierarchical density problem

reflective manuscripts such as color paintings, prints and photos, the contrast of hierarchical density is relatively close. The overall density and level contrast of color transmission manuscript are very different. Generally speaking, if the density contrast is between 1.8 and 2.4, it is a medium normal manuscript, if it is greater than 2.4, it is a high contrast manuscript, and if it is less than 1.8, it is a low contrast input. The initial density is 0.3 ~ 0.5 as normal; Those higher than 0.5, regardless of the contrast, are caused by insufficient exposure (or development), which is a dull original; The contrast is lower than 1.6, and the initial density is lower than 0.3, which is caused by overexposure (or development), which is a thin original. The overall density and contrast of the color transmission manuscript are closely related to the lighting conditions, exposure and development processing of the original. The positions of the sections on the photosensitive characteristic curve of the image are different, and the density contrast of each layer changes accordingly, and the distribution state of its layers is different. For photographic art originals, the aesthetic adjustment is to focus on impression color and visual effect, emphasize the contrast effect of the picture, highlight the sense of light, emphasize color saturation, exaggerate and render the important colors in the picture, and highlight the visual impact of color. We should emphasize on making up for some deficiencies in the process of shooting and developing, adjust and deal with the relationship between color, light and shadow, light and shade, cold and warm, and space discoloration in photography art, and highlight the modeling effects such as tone, atmosphere, light and shadow, texture and so on. So that the original production has a strong sense of light, bright highlights, strong dark tones, giving people a sense of the beauty of light and shadow; It has strong color saturation, bright color and rich color changes, giving people artistic appeal of color; It has extremely high definition, clear scenery texture, fine particles and rich subtle levels, giving people a sense of reality. In actual production, because the dark tone of photographic pictures is easy to be biased, the black of objects is not pure. Therefore, the UCR/UCA function is used to correct the deviation, so that the three primary color version can achieve the effect of neutral black, and then the black version is mainly used, so as to achieve the effect of pure black, and better show the texture level of black objects. For originals with different levels of density and quality, the processing method will vary from manuscript to manuscript

(to be continued)

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