Second, the lack of manuscript processing
1. Color cast processing method
The true condition of different original tones can be observed more intuitively from the measurement of the three-color density contrast of the original and the depiction of the tri-color density curve. The most popular method of dividing the density range in the color printing reproduction process, which divides the entire density range of the original and the replica into four segments, ie, the entire density range between the highlight spot (white field) and the dark tone spot (black field). Divide into bright (also known as high-profile), middle tone and dark tone of the three segments, and the area less than the high light density is called extremely high light. There is also a five-segment density range, that is, in the above-mentioned four segments, an area with a darker density than the above is also called extremely dark. In the analysis of the original color quality, if the original three-color density and contrast are basically the same, indicating that the original is not color cast, the tone is basically normal. If the tone is complete, the levels are rich, and the distribution is reasonable, even if the total contrast is slightly different, it can be considered a normal manuscript. The color reproduction can be corrected with the normal color error data, and the emphasis is on the reproduction of the tone level. If the three colors of the original document have different densities, it means that one of the colors is biased, and when the contrast of the three color densities is substantially equal, the color is balanced, which is caused by the color fog. This partial color draft, the general tone level is also better, you can change the color separation picture high and low profile three-color dot record settings, and with the adjustment of the level adjustment to achieve full gray balance to eliminate image color cast. However, it is better to design a hierarchical replication curve that adjusts the balance of three-color gray according to the three-color density curve, so that the tone of the full-tone tone can be uniformly corrected. If the difference between the highlights of the original three-color density is relatively large, the three-color density of the dark tone is nearly the same, and the color cast is mainly displayed at the end of the high-profile region, which is unfavorable for high-level reproduction of the image. Although this kind of color cast can directly use the original color shift highlight point as the white balance and input calibration of the color separation machine, the input balance of the color separation machine is changed, but the color correction signal is also changed, and the high light to be retained is retained. Color also lost, data
Often inaccurate. It is better to design the tri-level version of the level reproduction curve based on the tri-color density curve derivation, change the recording setting of the high-light tri-color dots of the color separation image, and correct the high-order color cast accurately. If the original highlight three-color density is basically the same, only the dark tone of the three-color density is different, the density contrast is not equal, in the dark tones show a significant color cast. The tone level is slightly lost, and the high-level level is normal. You can change the color separation picture dark tone three-tone dot record settings, or add a color full tone background removal (only for mixed complex color role), to eliminate the tricolor record picture in the dark tone side of the color cast. It is also preferable to design a three-color hierarchical replication curve that adjusts the gray balance by deriving the three-color density curve, and correct the color cast with accurate data. If the original tri-color density curve is crossed, the image is high-profile biased to one color, and the dark tone side is biased to another color, which is the cross-color cast caused by the three-color balance of the photosensitive sheet itself. The levels of tone at all levels are not good. It is not easy to correct the color cast on the scanner or the color separation machine by changing the three-color level adjustment and recording settings. It is necessary to derive accurate adjustments based on the three-color density curve. Gray balance three-color level replication curve, guide its three-color level adjustment and record setting, can make its copying effect slightly improved. Differences in color cast density of 0.2 or more are generally difficult to correct. When faced with a more serious color cast, the color difference of the three color differences more color original, in addition to measuring its high light, dark tone density meal, it is best to add the middle of the original tone of the scenery should be neutral gray three-color Density, the color draft, needs to be based on the tri-color density curve, deducing the design to accurately adjust the gray balance of the three-color hierarchical replication curve in order to adjust the color cast on the desktop system and the color separation machine. However, when dealing with the color cast of the original, care must be taken to carefully analyze whether the image is really color cast, because some are artistic effects that the author intentionally created. For example, in backlighting photographs, due to the stress of backlighting works, the color tone changes greatly, and various color tone patterns can be formed. Some are based on warm colors, while others are based on cool colors. However, it must be taken into consideration that some shades of the backlight photographs look somewhat distorted. In fact, the author deliberately pursued it. Therefore, this type of manuscript cannot be considered as a color cast. Therefore, the manuscript should be carefully analyzed and fully reproduced during copying. Understand the author's creative intentions and accurately grasp the keynotes of the screen. The manuscript with obvious color cast not only requires very precise measurement of the three-color density data, but also needs to take into account the correction of color cast when color separation is performed. The tri-color version of the original copy must be used to balance the tristimulus of the original color tone. To be adjusted, redistribution adjustments must be made to their levels, which should be the focus of operations. The correction of the color reproduction error is based on the adjustment of the three-color version to the data of printing gray balance. Due to the change of the color shifter color signal, the color correction data will also change, which needs to be based on compensating the color shifter to eliminate the color shift after the color shift and chromatographic color combination data, and finally correct the color error.
2. How to deal with the issue of hierarchical density
Reflective manuscripts, such as color drawings, prints, and photographs, have relatively close contrasts in the density of layers. However, the overall density and contrast of color-transmitting documents are quite different. In general, the density contrast is between 1.8 and 2.4, which is an ordinary manuscript. It is higher than 2.4 for high contrast and less than 1.8 for low contrast. The initial density of 0.3 to 0.5 is the normal draft; those above 0.5, regardless of the size of the contrast, are due to insufficient exposure (or development), and are boring originals; the contrast is lower than 1.6, and the initial density is lower than 0.3, which is caused by excessive exposure (or development), is a thin original. The overall density and contrast of color-transmitting manuscripts are closely related to the illumination conditions of the manuscript, the exposure, and the development process. The segmentation of the image on the photosensitivity curve is different, and the contrast in the density of the layers is also changed. Its level of distribution varies. For the photographic art manuscripts, the aesthetic adjustment is based on impressions and visual effects, emphasizing the contrast effect of the pictures, highlighting the sense of light, emphasizing color saturation, doing some exaggeration and rendering on the important colors in the picture, highlighting the color visual impact. It is necessary to emphasize some of the deficiencies in making up for the shooting and the rinsing process, and to adjust and deal with the relationship between color, light, shadow, light, darkness and space in the photographic art, highlighting the styling effects such as color tone, atmosphere, light and shadow, and texture of photographic images. Make the manuscript has a strong sense of light, bright light, dark tone with intensity, give people the feeling of light and shadow beauty; have a strong color saturation, bright color, rich color changes, give people a color art appeal; have a high Sharpness, scenery, clear material, delicate particles, rich levels, giving a sense of reality. In actual production, the black color of the object is not pure due to the dark color of the photographic image. Therefore, the UCR/UCA function is used to correct the bias, so that the trichromatic version achieves a neutral black effect, and then the black version is dominant, so as to achieve a pure black effect and a better expression of the texture level of the black object. For manuscripts with different levels of density and quality, the processing method differs depending on the manuscript.
(1) Normal exposure and density contrast standards. The main parts are in bright and medium tone, and it is proportional to the brightness. It belongs to the best visual brightness range and is in the 4th to 6th level of the new system of brightness. This kind of manuscript black and white calibration is based on standard density values. As a result, all the information on the original and middle notes of the original can be reproduced on the scanning color separation sheet.
(2) Ordinary contrast originals. The low density is 0.3-0.5, the high density is 2.4-2.8, and the contrast is common. Near the standard manuscript, the high and low profile levels of the image can be expressed in the straight part of the photosensitive characteristic curve, with rich layers of intermediate tone, and the main level is in the middle light. Adjustment, leveling density level difference and the original scene is proportional, the tone is generally more normal, while the original contrast tone compression, according to the tone level of the tone reproduction curve close to the standard level adjustment, can achieve a good copy effect. Due to the different distribution of levels of the original tonal hierarchy, the same is the original in contrast, and the reproduction curve of the tone level should also be different. If the manuscript is clear, the subject is adjusted within the bright midtones, and the copy should be slightly deepened to satisfy the visual response. If it is a thick-tune manuscript, the subject tone is often within the medium-density range and should not be deepened. The reflection draft (except for photos) level reproduction curve can be between the above two.
(3) High contrast originals. High optical density of not more than 0.4, but the highest density of more than 3.0 manuscripts, mostly the contrast of the original contrast of light and shade is too large, the general middle tone level rich and complete, the ratio of the brightest and darkest areas is not large, generally not At the main level, only high- and low-key density jumps and increases the contrast. This type of manuscript, when selected for highlights and shadows, can generally be rounded off at both ends of the secondary level, in order to reduce the scope of its tone reproduction. The level reproduction and reproduction curve can be adjusted according to different levels of the image level distribution.
(4) Low contrast originals. The gradation contrast is below 1.7, and the low light density original document with a high optical density of 0.3 or less is often caused by overexposure or excessive development. Its main part is bright and thin, with high lightness. It is at the 7th and 8th grades of the new system of lightness. Most of the lighter midtones fall on the shoulder of the negative image characteristic curve. The brightness adjustment level is rich, but the density difference is small. , And a large proportion of the area. Make a deeper copy when making, to reduce the brightness, and approach the standard brightness. This kind of manuscript needs to strengthen the reproduction and redistribution of levels in the bright mid-tones, and the black and white field calibration density values ​​should be smaller. The light curves of the middle and middle tone levels should be slightly deepened to achieve better levels of contrast and visual brightness. The shape of the curve should be distributed according to its level, and its main body should be adjusted to be in bright or medium density range. At the same time, it is also necessary to use deepened and lengthened black edition to complement, so that the intermediate level of reproduction and reproduction is deeper than the level of the manuscript and meets the artistic requirements of visual psychology.
5) thick stuffy manuscript. High-density light sources with a density of 0.5 or more, or even more than 1.0, are often caused by insufficient exposure or underdeveloped images. Most of the image darkness levels fall on the toes of the negative image characteristic curve and the lower half of the straight line. The main body of this type of manuscript is darker and darker, and it is located in Levels 2 and 3 of the Shinsei Shinbiao System. There are few bright tone levels, and the dark tone levels are rich and the level difference is soft, and the area ratio is large. In the mid-range density range, the reproduction should be reduced by increasing the lightness in order to brighten the brightness and approach the standard lightness. 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 contrast of the image can be used as the 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. The contrast range of transmission originals varies greatly, and color prints have to be reproduced as a screen with a substantially uniform density range. This density range is mostly lower than the density range of color originals. In the separation and printing process, compression adjustments must be made. 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
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