Analysis of Image Design Skills in Packaging, Decoration and Printing (Part 2)

3. Handling of sharpness issues

The clarity of color prints is an important quality indicator for image reproduction. Except for the special artistic conception of imagery, at least a part of the hierarchy (the main body or the background) of each picture is always clear. The following are the general requirements for the sharpness of the print screen.

(1) The solidity of the image level outline. First, it is necessary to base the factual (ie, sharpness) of the boundaries of the manuscript hierarchy. At the same time, it also depends on the size of the aberrations of the plate-making optics, the thickness of the electronic color separation analysis and the recorded scanning spot, and the accuracy of the four-color image fit. In the whole process of copying and reproduction, the transition width of the image level boundary is gradually widened, especially enlarged copying. The level boundary reality cannot be restored. The sharpness of the borders of the print hierarchy just seems to be emphasized by the separation of the colors.

(2) The clarity of contrast changes in the two adjacent levels of the image, namely the fine contrast. If the density of adjacent levels differs greatly, the visual experience is clear. On the other hand, if the density difference is small, the level is flat and the visual is not easy to distinguish. The subtle contrasts are mainly determined by the secondary differences of the manuscript layer, and are also constrained by the duplication and compression of the tone levels and the distribution of the level adjustments. In the separation of color separations, the emphasis of the level boundary can be emphasized, and the visual contrast of the boundary of the level can be increased. The subtle levels of contrast can be substantially enhanced.

(3) The resolution of the manuscript or the print screen hierarchy, that is, the subtle degree of its subtlety, is the essence of the composition of the objective scenery objects, that is, the so-called texture. Prints are based on the fine-grained resolution of the original image, but are compromised by the resolution of the plate-making optics, the magnification, the thickness of the cable, and the impact of the four-color version. After the plate printing process, the fineness of the original layer cannot be restored.

In color separation and platemaking, measures such as false light masks and electronic effects should be adopted to add “trimmings” to the borders of the image levels, so as to emphasize the visual clarity of image layer duplication. The “trimmings” added to the boundaries of the copied image hierarchy include two visual effects produced by the width and height of the peak. The height of the peak positive and negative densities is non-linearly transmitted to vision, and only enhances the visual Mach band effect, but it is not easily visually decomposed. The size of the “trim” width is linear to the vision, and is too large (especially at the bright side of the border) to be visually discerned, giving rise to a stiff embossed sense; being too small is not conducive to producing a visual Mach band effect. Only with the appropriate combination of the width and peak height of the "trimming" can we produce visual Mach tapes that are clearly and unresolved, and at the same time enhance the visual illusion of subtle contrast and subtle levels of resolution. Therefore, the effect of the visual Mach band produced by the border “trim” is the measure of the quality of the hierarchical clarity and reproduction. Because of the visual Mach band effect and resolving power, it is based on a certain visual physiological physical quantity, and it is basically universal. Therefore, through the visual comparison of printed images and manuscripts, it is also a straightforward and simple objective assessment to make a clear assessment of the level of reproduction. For this observation, the printed product should be placed under suitable lighting and at an appropriate viewing distance. The smoothness, graininess, moire, spots, and unevenness of the print screen will affect the normal reproduction of the image sharpness, and can be directly visually perceived. The smoothness and granularity of plain clothes are mainly determined by the granularity of the original, and are also conditioned by the magnification and the slight emphasis on the initial action value (particle strength adjustment). Subtle emphasis on proper adjustment of the starting value can improve graininess but affect the emphasis of hierarchical clarity. Manual revision can also reduce the granularity and increase the smoothness and delicateness of the clothes, but it is easy to leave traces of manual repair. Generally, it will not get perfect results. Dot shape, dot uniformity, and printing dot quality of screening images affect the flatness of printed images. The poor quality or uneven quality of printed dots will destroy their smoothness and delicateness. The moire is caused by the incorrect angle of the screen, and 45° screen angle is used for the magenta version of the character screen, the cyan version of the scenery screen, and the black version of the Chinese painting. The quality of these surfaces can be verified by scanning magnification or micro-density measurements of their reflection densities to establish objective technical measurement standards. However, it is generally intuitive to make visual evaluations. It is both objective and simple.

Third, layout design technology

There are a wide variety of printed products, many of which are not composed of a single original or a simple piece of text. For example, pictorial, atlas, poster advertising, books, newspapers, etc., its layout is often composed of multiple patterns. This requires designers to carefully design the layout of the entire layout. Even if the entire layout has only a single pattern, there are still many aspects such as size, shape, color, shading, and composition. Layout design is usually done by professional designers. As a designer, you should understand the printing production, the customer's intentions and the reader's object, and have knowledge of design procedures and design principles. The current layout can be completed by the computer Workstations in the full-page imposition system and the color desktop publishing system. Operators can freely design the layout according to the designer's intentions and meet the customer's requirements.

Problems to be Noted in Original Photoengraving

Today, manuscripts are usually photographed with a photographic method, and black-and-white or color sequential manuscripts are scanned and color-coded with an electronic color separation machine. The photo-making process of line originals (such as line logo designs) is relatively simple, and the originals are scaled to the customer's desired size on a plate making camera. Exposed on special hard photosensitive film, after processing, forming an image. Operation should pay attention to the following issues: the first manuscript must first check the quality of the manuscript, and secondly if the manuscript is accompanied by color, to identify the color of the line and the background color of the manuscript, to find out the color sensing range of the photosensitive sheet used, if the color to Red and orange dominate, you can not use SO special hard color film to take pictures, because SO color film does not feel red. When you place the original, you must pay attention to placing it in the center of the original holder. If there are too many scrapbooks, it is best to make the direction of the light source shine parallel to the long side of the clip strip to avoid overshadowing the negative shade and reduce the revision time. Washed and dried yin pictures must be carefully checked for correct dimensions, whether layout images are complete (with or without omissions), whether the density meets the requirements, whether the layout is consistent, and whether lines, text, and color patches are clear and transparent. Checking the corrected Yin picture can be used to copy and copy the Yang picture.

2. Problems to pay attention to electronic separation

(1) Film linearization. The purpose is to match the developing machine with the extension so that the dot size is the same as the displayed dot size. If it does not meet the standards, it is necessary to adjust the voltage level or the development time so that it is in line with the development temperature is generally controlled at the developer recommended temperature of 28 degrees Celsius as well. (2) Determine the density of the original. Using a color densitometer to determine the contrast of the original and selecting the correct white and black fields can reduce the auxiliary time on the extension. (3) Determine the zoom magnification. Use a magnification meter to measure the magnification of the original and enter the number in the extension. (4) Loading. First, the original document is cleaned, and the ruled line is added to the reflection original document. Then, it is attached to the scanning roller, and the size of the virtual light hole is adjusted according to the ratio of the scanning line and the fine contrast. (5) Calibration. Can be divided into the machine calibration (white balance): eliminate the error of the image signal input part of the extension, so that the electrical signals output by each channel are the same. The original calibration: first set the highlight, then set the dark tone, and finally set the middle tone, and then back to check whether the highlight tone is correct, the calibration point selection has an effect on the copy image level and color reproduction, while the original calibration, The gray scale can be used to calibrate, to ensure that the original color balance is not destroyed. Percentage calibration of recording outlets: The percentage of bright spot, high light, and dark tone of recording dots on a color separation film shall be determined according to the printing method, working conditions, and raw materials used in the subsequent process. (6) Set the starting line. The starting line, ie the cutting line, is defined for the size of the specification and is mainly a positive scan. (7) Pieces and Mountings. Cutting the photosensitive film should be larger than the size of the specification, there is a margin around the photosensitive film into the cassette, if there is no electronic screening device, the scanning dot film should cover the contact screen on the photosensitive film, and then hang the cassette on the extension. The loading takes place in a dark room with safety lights. (8) Scan. According to size and machine performance, sweep four colors, two colors or scan one color at a time. (9) Development. After the scanning is completed, the photosensitive sheet is still ejected into the cassette, and then the photosensitive sheet is taken out in the dark room, input into the developing machine, and processed and processed by the developing device.

3. Issues to be aware of when using color desktop publishing systems

The technology development and rapid commissioning of the color desktop publishing system brought a reform to the printing platemaking process. Its color reproduction technology and product quality have leapt to a new level. The process flow of the color desktop system mainly includes the following aspects.

(1) Environmental adjustment: Set the environmental parameters of the software by making the images seen on the computer's display screen basically consistent with the printed images. Because the colors displayed on the computer's display screen are related to the surrounding light conditions, the same image appears dull when the ambient light is strong, and looks relatively clear when the ambient light is weak. People feel different about the two. In addition, the effect of printing the same image using different papers and inks will be different. Only by adjusting these differences can we achieve a consistent effect between the screens we see on the screen and the printed screens. Color processing editing software has the function of environment adjustment. (2) Original scanning: scanning the original image via a scanner connected to a computer workstation to obtain digitized information of R, G, and B color values ​​for each pixel of the original image. (3) Revision: The original is revised on the computer workstation, such as improving the contrast, increasing the clarity, and the bottom. (4) Color screening: The processed image is converted from R, G, B to C, M, Y, and K on a computer workstation, and an image is divided into C, M, Y, and K colors. Monochrome film of information, and screens each color separately. Since the early 1990s, random outlets (FM outlets) have emerged and have entered color desktop publishing systems, with the potential for large-scale promotion. The biggest advantage of random mesh is the elimination of moiré; it supports the color separation beyond the four colors of C, M, Y, and K. It is not limited by the dot angle; an imagers with a lower resolution can be used, since the hierarchical rendering is not achieved by adjusting the size of the dot, and therefore is not restricted by the fixed relationship between dot lines and resolving power. (5) Imposition: In the computer workstation's imposition software, many images and texts are squeezed into a layout according to the user's requirements. (6) Proofing output: Sample proofs are delivered on a color printer connected to a computer workstation and submitted to the customer for acceptance. (7) Imagesetter outputs four-color film: Four half-tone screenings of the same version of C, M, Y, and K are output sequentially on a laser imagesetter connected to a computer workstation. (8) Raster image processor (RlP): It is the controller of an image-setter, usually a dedicated computer as the core. Configure a certain amount of memory and external memory, built-in Postscript interpretation software, and corresponding fonts, accept interface input data, output page dot matrix, directly to the imagesetter, output by the imagesetter. The color desktop publishing system uses a computer as the core as a workstation, and is equipped with an input scanner, an output color proofer, or a laser imagesetter to form a set of colors that can simultaneously process text, images, and output entire pages of color proofing pages or color separations. Platemaking system.

From the perspective of image quality, the DTP system does not output a full page, and the image magnification generally does not exceed 6 to 8 times, which can achieve the image quality of the electric extension. At the same time, it can actually integrate text and image processing and layout into one, with illustrations and drawings, greatly simplifying the platemaking process. From the view of software compatibility, the color desktop publishing system mainly uses general-purpose computer hardware and related software. The production volume is large, the cost is low, and the replacement and replacement are rapid. The performance cost ratio of the system is obviously superior to the electronic color separation machine and the whole page imposition system. From the perspective of system openness, the configuration of the color desktop publishing system is very flexible. The input, output, workstations, and network selection are all determined by the user's productivity, quality requirements, investment ability, and market demand. Different system grades, different hardware and software options, the price difference is very large, the distribution of hardware or software is often not a company development and production, but