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.
1 Issues to be aware of 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.
(to be continued)