Important adjustments before printing of color prints
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Printed originals require four-color electricity for the system-version. Apple's color separation manuscripts include reflections (such as color pictures, drafts, watercolors, oil paintings, Chinese paintings, new year pictures, gouache, etc.) and transmissions (such as color reversal films (natural color positive films), color negative films, etc.). The color negative on the negative manuscript is opposite to the original scene, and the color is complementary to the original scene. For example, the opposite color of magenta on the negative film is green; the opposite color of yellow complement is blue-violet; the complementary color of red is opposite. The shading on the original is the same as the original scene, and the color is exactly the same as the original scene.
The printed copy transmission is a visual image formed by the transmitted light. The reflective document is a visual image formed by reflection of the original under illumination of the light source.
The tone of the printed matter is that the color is classified according to the brightness and darkness, and the color reproduction, tone reduction, texture restoration, and resolution reduction are achieved in the copying work of the printed product. The color reproduction is accurate in hue, and the copied and printed products truly reproduce the color of the original, without color cast and without mottle.
The ideal tone reduction means that the tone on the original is faithfully restored on the printed product to meet the original copying requirements. Since the maximum recording density of printed matter is 1.8, after reaching 1.8, it becomes a straight line parallel to Dt (original density), so it is necessary to adjust both the reflective and the transmissive draft, in order to compress the contrast and correct the chromatic aberration to achieve the appropriate The range of print reproduction tones.
For example, the highest density on a color positive original is Dt=3.0, and the maximum recording density of a print is Dr=1.8.
According to the curve, the reproduction of the printed matter can not achieve the highest density reduction of the original, because the materials used in the reproduction of the printed matter include ink, paper, photosensitive materials (film, PS-version -), color sequence, and printing machinery. Limit, the maximum recording density Dr=1.8, but when Dt=3.0, the highest density of the original is large, and only the contrast can be compressed, otherwise the actual effect will not be printed.
Prints often require a tone adjustment when the tone is restored. When the density contrast of the original is larger than the highest recording density of the printed matter, in order to make the various tones of the original appear on the printed matter, it is necessary to appropriately adjust the tone reduction. Secondly, in order to adapt to the copying requirements of some special manuscripts (such as bright-based photos, dark-key photos), certain tones of the original must be appropriately emphasized, and other tones must be compressed accordingly. The main feature of linear compression is the equal scaling of the various grading segments. Linear compression does not represent true visual proportional compression, because the D-Y curve is also non-linear. After this compression, the bright focus is on the human eye. It is not easy to distinguish, resulting in a "grey level" phenomenon.
The reproduction of the tone refers to the relationship between the original density and the percentage of duplicate dots.
To make all the tones and colors on the original appear on the printed matter, first select the correct level curve. The level is the basis of the tone and color change. If the level of the picture is not rich, the performance of the color must be monotonous and boring. Only when the level is realistic, can the vivid color change.
It is impossible to faithfully copy the original, because most of the original density contrast is greater than the density contrast of the printed matter, so the copy of the print must be compressed.
Therefore, it is necessary to lose the subtle level of the part. In the actual operation, the reasonable level curve should be adjusted according to the contrast of the original and the specific content of the tone, that is, the level of the secondary part on the reflective draft or the transmissive draft.
Compression, focusing on the main parts of the hierarchy, highlighting the characteristics.
Under the premise of the normal contrast of the color draft, the gradation curve is correctly adjusted according to different types of originals.
The level control of the Apple computer for electrical extensions and color separation is convenient and flexible. It can be locally reinforced or compressed, but it is important to pay attention to the balance of the gradation curve of the color separation slice. The neutral gray balance should be appropriate, and the incorrect gradation curve will distort the replica. Therefore, when operating the extension and Apple computers, pay special attention to the correct use of the hierarchy, but for the entire color cast of the original, it can be corrected by adjusting the hierarchical curve.
When compressing the original gradation contrast, in general, the following methods are often used to compress certain parts.
1 Under normal circumstances, the normal manuscript, the contrast is appropriate, should make the low-key level to be flattened, especially when it is necessary to emphasize the middle tone and the brightness level.
2 The original is boring, and the tone is flat. If the emphasis is on the dark tone and the middle tone level, the middle tone level will be flattened accordingly.
3 The contrast of the original is boring, and the whole painting-face-low-adjustment-face-product-large is supposed to open the low-key level, but the middle-tone level is flat.
4 The intermediate adjustment level is relatively flat, the contrast is small, and the brightness adjustment level can be compressed, so that the middle adjustment level contrast is larger.
5 Original contrast is basically suitable for printing and copying. It is a photo with a middle tone. The dark tone - face - product - is small, and the dark tone level can be compressed to emphasize the middle tone level.
6 often encounter color photos, these originals are thin, the contrast is small, for these originals, you can compress the light and dark levels, making the contrast of the intermediate level is larger.
7 encountered the original light level flat, the contrast is small, you can open the bright level, but the middle level is flat.
The contrast of the natural color positive film of the transmission manuscript is relatively large, about 3.0, usually the compression contrast is needed to achieve the copying requirements of the printed matter; while the contrast of the manuscript of the reflective manuscript is small, the original is boring, according to different original features. Make a bright copy. For example, the copying point of a portrait is the color of the character, and the two colors of y and m are the key; the focus of the landscape is the natural scenery, and the two colors of y and c are the main points. Flexibly use the hierarchical travel button, adjust the reasonable level curve, correct the deficiencies of the original, maintain the main part, and correspondingly lose the secondary part, boldly choose, try to replicate the better effect. However, if the adjustment of the level curve is unreasonable, it may cause the image to be reversed first, the level is unclear, and the hue is inaccurate.
The color reproduction of printed matter mainly has the disadvantages of insufficient basic color, and the opposite color is excessive. To copy high-quality printed products, it is necessary to deepen the basic color without losing the level. The basic color should reach 100%, the moderate basic color should be full, the light basic color should be appropriate, and the bright basic color can not be lost.
The opposite color should be appropriate. Since the purity of the ink on the market is not bright enough, the hue and transparency are poor, and the whiteness of the paper is poor and the smoothness is poor. Therefore, when using the color, it should be noted that the brighter color complementary color (the opposite color) is smaller and thicker. The complementary color of the color should be used. The brightest face-face-product color complementary color can be used, so it plays the role of color change and contrasting layer. When used properly, the basic color can be made more vivid, thick and rich in color.
The color reproduction of the printed matter is actually an additive color reproduction of the primary colors y, m, and c of the color material with the reduced color light as the primary color. The three primary colors of y, m, and c color are the basic three primary colors of all colorful colors. Black – version – can not afford any color change, black – version – the role is only to stabilize the gray balance, play a skeleton role in the color picture, make the dark tone darker, emphasize the low-key level and contour, enhance the thickness and three-dimensional of the picture sense. The three primary colors of y, m, and c pigments transition to the black field, that is, y+m+c=approximate black. A part of the formed neutral color (three primary colors) is removed from the three primary colors of y, m, c and replaced with black ink. This is the method of background color removal (UCR) for electric extensions and Apple computers. There are many reasons for the removal of the background color: 1 Improve the suitability of printing, generally used in the dark adjustment, in the dark adjustment area, if printing with three primary colors, the dot-face-product is often very high, in high-speed multi-color printing It is easy to produce problems such as excessive ink layer and paste-version. If the background color is removed, the amount of ink is greatly reduced, and the amount of color inks of y, m, and c is mainly saved, and the printability is improved. 2 is conducive to controlling the neutral gray balance.
Black - version - the length of the tone depends on the amount of y, m, c three-color background removal, the amount of background removal is large, the middle tone, the dark level is flat, black - version - can be appropriate to lengthen the tone, to Compensate the three colors – version – the level of loss. If the three-color version – the amount of removal is small, the black – version – the tone can be appropriately shortened to avoid the middle tone. The dark tone is generally scaled to the maximum density of the image, which satisfies the image tone. To be calibrated according to the characteristics of the original, pay attention to the color balance of the dark tone, and at the same time, the dark calibration should also consider the relationship with the background color removal (UCR).