The role of black edition in color reproduction

The main reason for the use of black in color reproduction is that the Y, M, and C inks we use in printing are not pure and cannot be saturated with saturated black. Adding a black version to color reproduction can increase the contour level and detail contrast of dark areas.

The black version can be issued as a short-order black edition, a medium-order black edition and a long black edition. Short-term black version, also known as black version of the skeleton black version of the work, mainly reflects the dark tone of the original level, enhance the contrast of the picture, and stabilize the color. The medium-tone black double-lined linear black edition suits the originals of color and achromatic coexistence, such as scenery and grey buildings. The long blacktone version refers to the black version generated using the principle of background detachment. Its reproduction scope is relatively large, and it is applicable to originals with achromatic color, for example, black-based Chinese paintings.

With the advancement of modern printing technology and equipment, the printing speed of the printing press is getting faster and faster, the drying time of the ink is shortened, and the printing is changed from wet pressing to wet pressing, so that it is necessary to complete color reproduction with less ink. For this reason, a copying process in which black ink replaces part or all of color inks, that is, a non-colored structure, has been developed. This copying process can ensure the high quality of image reproduction, and it can also disregard the background color and expand the role of the black version. The entire tone range.

First, the black version of Photoshop

The color desktop publishing system is different from the electric extension when dealing with black editions. It has a separate black edition setting and black edition adjustment function. According to the need of copying, it is possible to arbitrarily adjust a plurality of parameters in the generation of the black edition, adjust the shape of the black edition curve, determine the starting point, the ending point, and the maximum outlet value of the black edition. High-speed, large-scale, wide range, to meet the requirements of various types of original copy black version. Such as Photoshop software separation parameter setting (Separation Setup), which set the color separation parameters related to non-color structure technology.

Open the Separation Stup dialog box, from the File menu, select Color Settings, open its child, select the Separation Setup command. Among them, the GCR in the dialog box is replaced by grey components, and UCR is the removal of background colors. One can choose one of them as a reasonable method of using black ink when separating colors.

In general, UCR can be used for color separation when printing on non-coated paper or newsprint. GCR is the default option for the separation mode when art paper is printed. When using grey component replacement technology, more black ink will be used in a wider color gamut. Compared with UCR color separation methods, GCR color separation tends to reproduce dark and saturated colors, and print or print images. The gray balance can be better maintained.

1. Black version generation settings

Black Generation is used to determine how much black ink is used in UCR or GCR for background removal or gray component replacement.
For GCR color separations, the user needs to select the degree of black generation, as well as the ink limit and the specified background color gain. In the Spanture Setup dialog you choose from several black generations.
1) The Mdium option is the system's default option and will provide satisfactory results in most situations. The Light and Heavy options in the dialog let the user slightly reduce or increase the effect of the Medium setting.
2) The None option does not produce a black version when separating colors.
3) The Maximum option maps the grayscale value directly to the black generation value. This option is used for bright black background images on a bright background.
4) The Custom option allows the user to manually adjust the black generation curve.

2. Use custom black options

1) Select from Black, Medium, Heavy, or Maximum a black generation surface that is close to the desired music, and get a black generation curve, which is used as a starting point for customizing the black version.
2) Select Custom from the Black Generation list to open its dialog box.
3) Place the cursor on the curve and drag the mouse to adjust the black curve. When adjusting the black version curve, the cyan and magenta yellow version curves will be automatically adjusted due to the changes in the black version curve and the total ink volume.

3. Black ink limit

Whether it is UCR color separation or GCR color separation, the ink volume limit value entered in the Separation Setup dialog box is used when generating the black version. The total ink limit is the maximum ink density supported by the same energy. By default, the limit for black ink is 100%, and the total ink limit is 300%. It is necessary to check with the printing factory to confirm whether these values ​​should be adjusted.

Black Ink Limit gives black ink an upper limit. For example, if the black component is obtained without color separation or gray component substitution, 50% is obtained, and if black ink is limited to 70%, the maximum background color is removed by 20%.

4. Total ink limit

The Total Ink Limit limits the total amount of ink that can be printed. If the original cyan ink volume is 90%, the magenta ink volume is 87%, the tribute ink volume is 85%, the black volume is 7%, and the original ink volume is 332%; the total ink limit is 302%. 0% background color removal.

5. The Color Gain (UCA) option in the Separation Setup dialog box is used to increase the ink after removing the black ink in the dark tone area. The effect is opposite to the bottom color removal. It is the color ink that increases the dark tone area. The amount of thorough UCR is the same. For those areas where printing with black ink alone will show a flat tone, using UCA will produce a rich dark tone.

The UCA Amount gives the same percentage as the background color removal. Photoshop will increase the amount of color ink in the shadow area during color separation. Increasing the amount of background color gain increases the amount of C, M, and Y inks that are removed. The range of available ink is from 0% to 100%, which can be matched with the printed three-core to obtain the optimal value. If you can't confirm this value, you should leave it at 0%.

Second, the role of the black version in color reproduction

After long-term practice, human production generally believes that the role of the black edition in color reproduction is as follows:

1. Improves the stability of gray balance

Y, M, C three primary colors ink to achieve a neutral gray balance is more difficult, the use of background color removal process, the neutral gray balance is basically not affected by the color ink, mainly by the black ink to achieve neutral gray copy. Therefore, the gray balance is easy to implement.

2. Increased print density and contrast

According to the current conventional conditions, Y, M, C three-color inks have a density of 1.6-1.7 after superimposition, and people's visual ability for dark debate can reach 1.8-1.9. Therefore, the black version can enhance the paper's absorption of light, the light absorption rate can be increased from 96% to 98%, the density increases accordingly, the tone is extended, the screen is improved, and the three-dimensional image and space are enhanced. Feelings make the picture vivid.

3. Increased the level of intermediate tone to shadow tone

In the color reproduction process, the rule of tone reproduction is that the tone zone level is maintained and emphasized, and the intermediate tone zone level is maintained or slightly compressed. At present, the emphasis of the black-tone tone expression is generally midtones to the dark tone region, which makes the dark tone region prominent and improves the visual effect of the picture, especially to meet people's visual requirements of the text. Color copying requires graphic and textual, from the visual requirements, black text is the best, easy to read.

4. Expands printability and reduces printing costs

Black ink can be thought of as C, M, Y color ink and other things. Therefore, some parts of the picture can be removed some or all of the three primary colors, and black ink is used instead. This will not only satisfy the tonal requirements of the image, but also reduce the use of ink and reduce the printing cost. Similarly, the density of black ink is higher than that of other color inks. When black ink is used in place of three color inks in the mixed color area, the total amount of ink is reduced, not only avoiding the accumulation of ink layers in dark areas, but also the drying speed of ink. Accelerated, reduced sticky phenomenon, improved printability, to meet the requirements of high-speed, multi-color wet-press printing.

In short, the existence of the black edition is the requirement of the objective conditions of printing. In today's situation where the ink does not meet the ideal requirements and printing is still dominated by pressure printing, the production process of the black version will continue to improve with the development of the printing industry for a long time.




Source: Ke Yin Network