Pre-reduction and post-processing of scanning color separation technology (medium)

Fourth, pre-scan restore

The standard reduction of pre-scan color separation refers to the use of standard transparent, reflective gray scales and color standard test tools for copying experiments based on manuscriptability conditions, using manuscripts as a benchmark, and establishing four standard texts. When scanning, only The calibration of black and white fields, and the use of the four standard documents already established, can achieve a good reduction effect.

1. Create a standard gray balance file

One of the fundamental principles of color reproduction lies in restoring the gray in the original. Therefore, under a certain printing condition, a standard ash scale should be used as a manuscript for copying. Through experiments, C, M, and Y primaries are overprinted with different dot values, so that the levels in the original manuscript can be restored. Gray, the value of this set of gray balance parameters is stored as a standard file, which becomes the basis for restoring the original gray.

2. Create a standard tone level curve file

The tone curve of the tone is the abscissa of the standard gray scale, and the gradation of the dot of the color separation film is the relation curve of the ordinate. Through the scanning and publishing experiments, a standard curve file corresponding to the density values ​​of all levels of gray scales and the tone points of the color separation patches at various levels is established, and used as a standard density contrast original document application. At the same time change the midtone curve, establish a few preset curves, respectively +5%, +10%, -5%, -10%, etc., to be stored for the selection of different density contrast manuscripts.

3. Create a standard color correction

Based on the input gray balance, according to the characteristics of different manuscripts such as transmissive manuscripts, reflection drafts, and prints, the six hues of CMYRGB on the standard transmission and reflection color standards are used for manuscript copy experiments, and the 24-channel color correction parameters are adjusted. After proofing, the six hue of these three types of originals can be accurately restored, then other colors can also be restored. The color correction parameters of these three types of originals are used as the standard color correction files, and are stored thickly for the three originals. Restore selection.

Even if there is no platform scanner for the color correction system, Photoshop's selection function can be used as a supplement, especially when the image RGB mode is converted to the CMYK mode. In this function state, the standard color standard can be used for standard color calibration. Specification, and standard school color quantity parameters are thickly stored, loaded after each image scan, so that it is not necessary to adjust each color gamut of each figure, and the effect of restoring original hue is also achieved.

To establish a standardized color correction document, we should try to achieve both the color saturation and the color hierarchy. Whether the effect and adaptability of this standard color correction quantity is wide can reflect the level of standardization of color correction. The 24 standard color correction parameters should also be continuously revised in the production practice to make color reproduction more accurate.

4. Create a standard sharpening file

The general color separation software for high-grade scanners and high-grade scanners has an automatic sharpening function and automatically sets the sharpening amount according to the magnification. Should be based on this, and then according to the original content characteristics, do different settings for the amount of sharpening. Through experiments, preset several sharpening amounts. Such as: gold and silver bronze utensils, scenery photography, portrait photography, Chinese painting, oil paintings and other sharpening documents, for all types of manuscript selection, in order to achieve fine grain and excellent sharpness effect.

The above four basic standards are interconnected. After a good document is established, stable scanning and color separation can be performed. The author establishes these four standard documents through repeated experiments on various electric extensions and scanners. In practice, the research concludes a law that is called the classic law by peers.

That is, as long as the gray balance curve established by the electric extension and the scanner is accurate, the gray in the image can be restored. At the same time, the complex color (composite color, tertiary color) in the image can also be restored, and it is not necessary to adjust the ratio of the dot values ​​of the three primary color versions in the gray in the later period.

According to scientists, of the more than 100,000 colors that are discernible, more than 80,000 are ash-containing colors. In other words, the thousands of complex colors contained in the image should belong to the category of restoration. This classic law makes our school coloring and color correction work in a regular manner, and can be more scientific, more accurate, and simpler.

Some originals have gray and complex colors that need to be adjusted. Only the brightness of the original is adjusted, that is, the density of the original color is light or heavy. This adjustment should use the Y, M, C tri-color curves for simultaneous darkening or lightening adjustment.

In summary, a standardized recovery file for scanning color separation is established, and the best image information is directly obtained from the manuscript by using an electric extension or a scanner to ensure a good reduction of the color of the image, no matter whether it is a high-end product or a middle or low grade production. The products are the first work. Especially for the production of artistic pictures such as paintings, it is particularly important to reproduce the original beauty of the paintings, the depth of the artistic conception, and the artist's unique temperament, style and characteristics, because the artistic conception in the works is impossible. In the late processing transferred out. This is also the scientific nature of the scanning color separation technology. We should treat it with a scientific attitude and do it carefully and carefully so that we can get twice the result with half the effort.