Section 11 Photomechanical printing
Most printed images and prints are expressed in a binary binary system. The expression method is either black or white, and the intermediate color part of the image is not represented by the ink density, but by a dot matrix of different sizes. The arrangement of light and shade produces a visual change effect. With an array of fine and tiny dots, under most appropriate reading distance and visual analysis, the existence of dots is invisible. This expression technique or technique is called Halftone halftone or halftone dots. Since the dots are very detailed during application, we regard halftone dots as gray or colored intermediate colors. In color printing, we use the halftone dots of the three primary colors of C, M, and Y to express. The overlapping dots or full version of the three primary colors form tens of thousands of different colors and gradations. Due to the thickness and density of the printed ink , Can not form enough black and dark tone levels, so color halftone printing, in addition to CMY, plus black halftone printing, to increase the density and gradation of dark and black areas, forming the majority of CMY + BK color four-color subtractive French printing system. The halftone dot printing layouts include letterpress, flexographic (resin letterpress), lithography, and gravure. In different printing methods, gravure is a corrosion method or an engraving method. The depth of the ink hole will also represent the different levels of ink color, peace. The difference is that the lithography is different in size of each dot, but the printing color density is consistent. Today, more and more digital toner imaging and electronic ink imaging also use halftone gradation to achieve a more stable printing effect. Accurate angle alignment, using C cyan, M magenta, Y yellow halftone dot printing on white paper, can produce R red, G green, B blue colors, during which CMY three colors overlap to produce black phenomenon. The electronic scanning color separation machine that is widely used today was designed by Hardy and Wurzburg in 1948, but at that time there was no electronic hardware software that could support computing. So in 1948, the scanning color separation machine was changed to a continuous version, which is not a screen passing mode. Today, the screen passing conditions are much easier than before.
The left side needs to be trimmed and the right side is not trimmed
The dot increase value during printing is a big factor in the reproduction of printing, including any change in the process of the process. On the other hand, the dot change of the dot transfer of the printing machine, and the paper absorbs ink and paper fibers. The large size of the capillary ink absorption, and the depth of the reflective layer on the paper surface, these multiple problems have formed a complicated cause of dot growth. Insufficient purity of each color ink produces unnecessary turbidity. On the other hand, it is a problem of unsatisfactory density. For a long time, manual color correction, intermediate color correction, negative film correction and electronic scanner electronic circuits have been used for a long time. Color correction, color correction of image software, all want to produce better color reproduction. All image or signal corrections, whether optical or electronic, reduce or eliminate the original impure color, a color correction image with unclear margins, or a blurry marginal information, help to improve the original There is an image or marginal copy sharpness. This kind of color correction film or color correction signal called USM (Unsharp Mask) all improves the edge sharpness of the image. Because a very sharp color correction image, it often tends to Reduce the contrast of the image margin, that is, the original height difference is 0.9 density, and now use a third density correction film 0.3, so the marginal difference is reduced to only 0.6 to make the contrast lose one third, and the marginal sharpness will be reduced. Therefore, there are USM color correction films that reduce the sharpness of the image to form USM unsharp color correction films. This reduces the sharpness of the new image after color correction. Instead, it uses sharper image correction films to obtain sharper images. That is to say, the marginal contrast of 0.9 was originally. Now due to the blurring of the signal, one-third of the color correction mask Mask, when there is USM, only the density difference of 0.05 to 0.1 is subtracted at the marginal place, instead of a substantial reduction of 0.3, so compared to Compared with the overall layout, the marginal signal has a sharper contrast reproduction. It is used in the USM of electronic scanning signals, that is, the high-contrast signal is straight up and down during scanning, and becomes a gentle slanted signal after scanning, because the scanning light hole is scanned like a spiral, and the formed signal cannot go from there to no. , From scratch to like, the cutting type immediately changes over, but changes from one side to the other one by one, forming a gray zone that does not change immediately, so the USM signal is to reverse the scanning signal of the larger aperture When the white is going to be black, the white signal is whiter, and the black signal is blacker when it is black, so that there is a greater contrast at the margin to make up for the weakness of the signal's oblique line. In terms of electronic signals, in addition to the USM method, the gamma r value can be adjusted higher, so that the overall picture contrast is greater, and a sharper and more spiritual picture is obtained. But where the margins are already alleviated, the picture cannot be lifted up because the marginal signal gap is small, so it cannot be separated. Many people regard USM adjustment as a panacea, and each time it is greatly increased, the overall contour of the entire image will become clearer, but many black lines and white lines are interlaced, and the picture often loses the expression of the front and back sense. The embossed effect that becomes almost completely flat, the sharpness is false. The whole picture originally wanted to represent the three-dimensional space phenomenon in two-dimensional plane, and it became only the two-dimensional phenomenon, so USM can be used moderately, otherwise The phenomenon of excess is worse than inferior.
Scanning color separation images can make different image changes
GCR (Grey Component Replacement gray replacement) is a color separation method that can be used to mix CMY three colors to form turbidity, gray, and dark local dot percentages. All or part of the percentages are replaced with black dots to form a three-color ink. The increase in black monochromatic ink can reduce the percentage of overprinted ink, reduce the ink drying time, reduce sticking, reduce the amount of ink used and cost, the printing speed may also increase, and the set of pairs and the sharpness of the print may also be improve. In addition to the comprehensive replacement of GCR, it is also possible to use UCR (Under Color Removal) that performs gray replacement after 40 to 50% midtones to replace most of the functions of GCR without affecting the highlight. Color or four-color nets form a fine texture with denser dot patterns, so the use of GCR and UCR have several differences. An electronic scanning color separation machine is used in the photocopying and printing industry, making it easy to use USM to adjust image sharpness, GCR or UCR neutral or dark color replacement system, Tone Reproduction version to adjust reproduction adjustment, and undesirable The functions of color elimination and color reproduction saturation adjustment are all concentrated on the electronic device to do various copy adjustment functions without having to spend a lot of cost to complete the high-quality color image copying operation, ★ barrel scanning color separation By scanning the extremely small light hole of the receiving head, the color image signal is received, and the three signal strengths are filtered out by the RGB three-color filter, which is received by the photomultiplier tube of the rear Photo Cell. This ray vacuum tube can weaken The optical signal is amplified to tens of thousands of times, and the power supply circuit is used to adjust the combination of image, version adjustment, gradation and color reproduction. There is a larger optical hole outside the small optical hole. This unclear USM signal is used to communicate with the main signal. Compare, make an unclear signal to invert to enhance the sharpness of the main signal, some advanced scanners that can change the aperture of the USM signal can set USM effects such as line width Select the starting point to change the color contrast is also possible, which is currently the most low-level ★ tube scanner, flatbed scanners to digital cameras can not do the advanced tuning effect. These main image signals, combined with the sharpness adjustment effect, form a direct laser exposure halftone color separation film of C, M, Y, and K color separation films. Generally, at least a 12 × 12 laser beam is required to come It is more reasonable to form a 1% to 99% dot, that is, a 150-line dot. It is necessary to use six beams to form a line at 1800dpi, and to scan 1800dpi output by sweeping left and right twice and front and back electronic signal exposure, and replace it with 120 lines. As long as 1440dpi can achieve 20% faster imaging at the same speed, on the contrary, 200 lines require 2400dpi to image, and the exposure increases by one third. The new generation of CTF film output machine, CTP direct computer printing plate output machine, most of the commercial printing output at 2400dpi up and down, so it has a maximum of 200 lines /? Jealous? 闶 涑 觯? 诒 ㄒ 稻 tor? 200dpi, output Up to 120 lines /? Jealous? Contrary? Fortunately, Tiao Jun T? EPS high-end computer group page system, all use dot matrix files to operate, only black and white files are relatively small, the amount of other color image files It is very large, it needs to adjust the layout, color and shape changes through the mini-level computer, remove the appearance, image combination, spray repair, color change, CEPS creates a new way for the design and application of printed color images, but the equipment is expensive, The efficiency is not high. In addition, when the CEPS appeared, the efficiency of the computer function was insufficient, and the storage space of the computer memory was also difficult to correspond. Therefore, in the early 1990s, there was a word processing capability DTP, a micro personal computer-based page grouping method, plus CTF The development of film output machines gradually replaced CEPS, forming an era of full DTP today. Under its open system architecture, drawing software, page grouping and editing software, plus video ace After the third edition of Photo Shop, it has become a quality output acceptable to the printing industry. Today, Photo Shop is not only used in print design, but also indispensable software tools in film, TV, and video creation. Two pages of CTF size are output and then manually grouped for large-page printing. Today, large-size output full-page negatives for printing. Multi-page CTP is used to output complete pages and complete pages. No film is used at all. In the process, material saving, manpower saving and There is a great benefit in quality improvement. At the same time, it also has great benefits in environmental protection and waste reduction, without using silver salt negatives. In terms of color proofing, all digital files have been output using CTF or CTP today. Kodak Singnature using color film mentioned by Professor Hant, Cromalin Proofing by DuPont, Matchprint by 3M or Color Key proofing using color layer overlay It is rarely used except for a large number of printing, because they can be printed on real printing paper and appear as transfer-type color prints. The definition of proofing is to give the user a sample in advance, which will indicate what kind of sample the printed matter will become in the future. The best proofing is for the printed product to look exactly the same. WYSIWYG is a combination of What You See Is What You Get, Chinese is defined as "seeing "Get what you get," don't be biased. Today, most people use inkjet to proof, so the paper used must be surface treated with inkjet conditions. The continuous proofing is very beautiful, but it does not necessarily match the printed product, so RIP is proofing. Interpretation will also be as proof as printed matter, and the effect will be more realistic. It is also a good method to use a toner printer for proofing, because a toner printer analyzed at 2400 × 2400dpi has appeared. It is feasible to use 150-, 175-, and 200-line dot output for toner printing. It is popular to print 150 lines in general commercial printing, 175 and 200 lines in finer commercial printing, 300 lines and 400 lines in very sophisticated high-level color printing. Generally, dots are arranged regularly, and the density of dots is used to express the density There is a different kind of FM FM network that shows the density of levels with irregularity and density of dots. It is also called Random random dot method, which can have higher resolution than 300 lines output at 2400dpi and 200 lines. The left and right lines are analyzed without worrying that images like fan nets, air-conditioning grids, and steel bars for pedal wheels are prone to misalignment. The remote proofing is divided into Hard Copy inkjet and printing methods, and some people use CRT or LCD screens for Soft Proof soft proofing. There are still considerable gaps. First of all, in terms of analytical power: CRT vintage cathode ray screens are very limited. LCD liquid crystal screens are also very limited, and printed products have higher resolution (such as 2400dpi). White spot color temperature: CRT D65 (50) or D93, LCD D65 (D50) or D93, printed matter is judged by D50 or other light source. Color gamut generation: CRT fluorescent materials receive electron rays to emit a spectral color gamut, LCD RGB uses filters to develop color, printed paper and CMYK ink pigments. Color generation method: CRT RGB additive color method, LCD RGB additive color method, printed matter CMYK subtractive color method. Background light source environment requirements: CRT and LCD, TV TV should be slightly darker, the screen can be average, the average environment of the printed matter can be average. Illumination of white part: CRT average about 150 / m2 candlelight, LCD 500 / m2 candlelight, printed matter from slightly dark to very strong lighting conditions. Dynamic density range: CRT depends on the surrounding luminosity, LCD has less dynamic density range than CRT, and the printed matter depends on the relationship between gloss reflection and light source viewing angle. Here, Professor Hant said that for color image printing, all kinds of paper will have very different concentration range changes. Due to the coating layer relationship of bright coated paper, the ink absorption is small, and the density range of 1.6 can be achieved under the surface reflection. , The rough non-coating value may be only 1.2 concentration value, and the newspaper is lower. (Editor's note: According to Professor Hant, when using CRT and LCD screens to compare with printed products for soft proofing, there is a considerable gap in the resolution of images and text, and electronic soft proofing can be partially placed and can be seen More detailed situation, make up for the resolution. The relevant color temperature is still within the understandable range, and the human eye can automatically adjust the ability to recognize the white point. The use of RGB color development and color rendering method and the use of CMYK printing on white paper are very important. The big gap, people who use the screen for soft proofing inspection must have the quality of the ability to replace the gap between the two, otherwise it can not be expected what kind of image effect will be printed out. The environment has an impact on the comparison of screen judgment. On the screen The contrast is adjustable, and it is fixed after the adjustment, and the viewing angle of the printed matter and the ink absorption of the paper have large changes, so with such an understanding, the difference between doing soft proofing will be less, and the ideal soft type will be obtained. Proofing evaluation). In addition, the editor's thoughts Note 1: The screen proofing case and the tacit example of hard proofing and the cognition of both printed products.
Section 12 Digital Printing Technology
Four-color film 300dpi thermal transfer imaging machine
Digitally printed images have very stable and descriptive pixel reproduction, but there are inadequacies in the layout stage. Using contour technology to reduce the insufficiency of gradation is the current application of technology. Use laser imaging technology, thermal color film transfer imaging technology, thermal wax transfer imaging, thermal wax inkjet technology, various inkjet technologies, Dithering dithering dot method, etc., which also has random error diffusion technology, etc., Generate different levels of expression. On the scan output system, very small imaging points are used to make different arrangements to form a gradation image. In the printing industry, there is a 12 × 12 dot file, which produces a good tone, using a 10 × 10 10μ exposure point , In order to produce extremely small print ideas, and with the proper allocation, it can produce an excellent 100 tone. The reproduction of the tone also involves the expansion of the dot, including the mechanical dot expansion, which is caused by the pressure transfer or creeping. The dot pattern is enlarged, and the optical expansion is also partly absorbed by ink and printing ink. Due to the effect of expansion and penetration on the surface of the media, the other part is the depth of the reflective surface of the media itself. If only 100% reflection from the surface of the media will not involve the problem of optical dot expansion, if the degree of translucency is less, it means from The shallow layer on the surface of the media can reflect 100%, and the degree of optical diffusion is relatively limited. If the media itself has high transparency, 50% of the dots may be judged as 70-80% of the dots, and the data will be expanded by 40-60 As much as%, if even the penetration value of the media is added together, the dot diffusion value of the media will increase a lot. For the analysis of the outlets, the normal normal distance is 250 lines /? The home book is knocked down? The ten outlets are the most elaborate outlets that ordinary people can resolve. So the most high-end prints are 250 lines /? Plus: ⑹ Qinmeimei? 75-line advanced printing work, 150-line intermediate printing work, 100-line printing newspaper rotary offset printing, 65-line letterpress printing quality. The earliest laser printing equipment used a single laser to move light at a high speed using a strip-shaped polygon mirror. Each mirror can rotate to move to reflect the scan line that scans the full frame. When the scan is completed, the next mirror also rotates. Generate another scan line side by side, with one mirror rotating and reflecting into one, so that the laser spot becomes a scan line, one side by one, one continuous side by side to become a full-frame scanning imaging surface, and laser scanning imaging in OPC organic The latent image of the photoconductor can be developed by Toner toner, transferred to the paper surface and then baked and cured into a laser printed image. Among these digital filmless proofs, there are 1. Color film laser exposure to form halftone dots, which are transferred to the paper or media to be printed after development. Since the laser can reach 2000dpi, 3M Matchprint can also be used. Up to 200 lines of output. The thermal color film transfer method is Kodak Approval, which is different from 3M Matchprint. It uses the heat of laser light to transfer the pigment layer on the color film to the intermediate transfer sheet, and then to the printing medium. This kind of project does not need to be developed. The resolution is up to 2000dpi, which is used for advanced proofing, and this digital proofing is interpreted according to RIP, forming a diversified network form. 2. Thermal color film transfer, directly forming 300dpi variable-size printing dots on the media, using four-color overlapping color dots as continuous color reproduction, this method is currently almost no one uses, because it can not form printing The dots, and the 300dpi four colors are all 90 ° angled straight dots overlapped on one point, to avoid the appearance of net flowers, the image can still be clearly seen visually, but the 300dpi resolution on fine characters is still very inadequate Office. There are Kodak Desktop Proofer and DuPont Cromalim 4 Cast, but Kodak's proofing can produce special colors such as orange and green. In addition, white, gold and silver foil hot proofing is also a major feature. 3. Inkjet printing proofing, currently using Epson's Stylus six-color proofing, using S-1000, S10600 and S-9600, 9800, 7600 and other machines, the latter three up to 1400 × 2880dpi, it is very appropriate to constitute the sampling point of the printed matter, The weaker one is that the proofing paper, except for the glossy and snowy surfaces, must be matched with the printing paper, or it is impossible to directly print the proofing paper with the printing paper like the transfer film method. Other HP, Canon, Agfa, Encad also have this Inkjet proofing is on the market. In the early days, Iris ’300dpi overlapping continuous adjustment inkjet dot proofing method was a very high level of proofing. It used each dot to express the density of the print in different sizes and sizes, in addition to incorporating Scitex ’s IRIS inkjet. , 3M's Digital Cromalin also has the same equipment product system. However, the continuous inkjet adjustment has a very thick tone on the plate tone, which is not similar to the halftone used for printing. This is also a painful complaint for customers who are not satisfied with the printed matter after the delivery customer compares the proofing in the future. The pixels of the digital page information file completed by the DTP system can be expressed in printing mode, or can be presented in different ways on the continuous adjustment of color photo paper, color film, and chemical processing. Like using a fine CRT color cathode ray tube, the color The digital image file of the page is displayed and focused on a small-size color slide for RGB exposure. Use RGB three-color laser light for color photo paper exposure, such as Fuji Pictrography, it also has procedures for transfer. Other reflection dimming image methods with DMD digital micro-needle points,
Slides, screens, printers, proofers, magazine paper, newspapers have different color gamut performance
LCD LCD screen exposure, LED RGB stripe and surface dot arrangement RGB exposure, Light Valve uses optical fiber and piezoelectric optical path control method or liquid crystal I / O control to do RGB color exposure on photo sensitive media, which It is a method of forming multiple images. Electrophotographic image forming printing technology is an important tool for office automation, quick print shops to digital printing of plateless printing. In addition to most of the toner development imaging, Indigo's electronic ink and Xerox i Gen 3 paste printing ink. The main body of the imaging receiver is OPC (Organic Photo Conductor), which is the earliest metal tube, and later forms a variety of conduction bands or other imaging modalities. OPC performs positive charge charging after cleaning, and then uses laser light or LED The light (diode laser array group) is exposed, because the negative charge of the light neutralizes the positive charge in the non-printed area. The signal of this light is formed by the exposure effect under the control of a 1-bit digital file of each color printing pattern. Therefore, once the positively-charged printed part remains after exposure, it will be adsorbed by the negative charge of toner or other developer, leaving the color in the positively charged part, and then transferred to the printed paper and media. The difference between this printing function and printing is that the printing pattern is changed at any time according to the 1 bit Tiff file of the page, and it disappears with the printing. Even if 100 sheets are printed, it needs to be imaged 100 times. The second is that it is not necessary for the entire printed page to appear at the same time. As long as the image is displayed section by section, even if the circumference is only 15 cm long, as long as the file is large enough, in theory, it is possible to print a pattern of 10 meters long or 50 meters long, and no seams appear. The laser light exposure is based on the rotation of the polygon mirror. Each mirror rotates to form a scanning line (also multiple lasers appear, which can form multiple scanning lines). At present, 2400 × 2400dpi high-resolution laser printing equipment has appeared , Can output AM200 line or FM FM outlets. Those using laser imaging technology include Canon, Xerox, HP, Tektronix, Kodak, and Indigo. The LED is used to line the entire screen at 600dpi, if the width is 12 ?? 305mm), there will be 7200 LED array imaging, like Xeikon using LED can reach 175 lines, mainly each LED contains 3bit = 8 stage Only by expressiveness can Océ and Japan OKI Electric also use LED array imaging. Today, it can print more than 100 A4 color printing devices per minute, which is more and more diverse, and the cost of toner has also been reduced a lot. There is also a new niche in network capabilities and mass production time and cost. Although the Kodak color film thermal method is only 300dpi, each dot size changes a better tone performance, and the color film uses gravure color density stability is good, and the 300dpi thermal wax film transfer method only provides 0 ~ 36 This tone is not suitable for color proofing. On Dithring technology, it provides a huge square dot of 0.3mm with a total of 50 lines of square dots, so the quality is not very acceptable. After changing to a random dot, the resolution has improved (and has not been developed). There are three inkjet printing methods, 1. Piezoelectric. 2. Hot bubble type. 3. Continuous inkjet. The third type of continuous inkjet is rarely used for image formation. 1. The piezoelectric type uses a transistor to drive the displacement of the valve in the ink chamber by the current, resulting in the ink jet phenomenon of compressing the ink chamber, and now the size of multiple ink dots can be displayed under current control, which changes the uniform resolution of the same ink dot, and Do not pick all kinds of ink, water-based, oil-based, environmentally friendly solvents to UV or thermal wax can be imaged, can also be used in other optoelectronics, circuit boards, semiconductor industry applications, for good quality fine ink dots and higher output efficiency, each group The number of action nozzles ranges from thousands to tens of thousands of points, so as to meet the thin and fast expectations. 2. The thermal bubble type is equipped with a resistor in the ink chamber. After being energized, the water in the ink is instantly heated to 350 ° to 400 ° C to generate rapid expansion of water vapor as a motive force. About 12,000 times, and the thermal bubble nozzle has a short life, and it is necessary to use water-based inkjet, otherwise it will not be stable and vaporization will produce a printing effect. The two sides of the valve are pushed by the ink head from the back of the ink head in a serpentine motion, and the ink dot size control is very new. It is a brand new technology. In different inkjet methods, provide different color gamut printing ink, and 6 colors, 7 colors or 6 colors CMYK + LC light blue, LM light red, and RGB three colors, plus glossy matte black, choose two A fluorescent color system that can spray 12 colors is also gradually improving the performance range of the inkjet color gamut. In inkjet proofing, ICC Profile can also be used to adjust the color gamut characteristics to respond to the changes in the color gamut reproduction of multiple papers such as coated paper, magazine paper, and newspaper. The color is the most versatile and the largest amount of information that humans receive visually. And the technological progress is also very diverse. Professor Hant ’s two-day extensive speech can be said to be "throughout the past and present". .
Editor: Professor Han Te has many procedures and calculation methods for calculating color reproduction or spectrum distribution in the lectures. Most of them belong to the color-related research and development class. The general users purchase color reproduction, image adjustment, and color management software for images. Attached to it, this article will not be quoted.
Note 1: The human interface between screen proofing and printed matter is necessary. The case of poor CRT image display still has some reference value. In 1990, a Crosfield 656M scan with color screen display scan image reproduction was purchased from the United Kingdom. For the operator to see the pre-scanned additive color image on the screen in advance, it is very helpful to adjust the layout and color settings. This is better than using only the button adjustment and LED display density, dot screen data to make a point judgment without a screen. A full-screen image is much better than a single point judgment, but after five years of use, the CRT screen is damaged and cannot be found on the market The low-frequency signal input screen finally found to be a double-frequency receiving screen. The image came out but it was very dark, and it was "barely" looking at it in use. Every time I went to the color separation room, the operator complained about the lack of brightness of this screen. I hope to change one, but I ca n’t find the old electronic parts. Since it ’s not so good, it ’s better to take it away. Just like the general scanner only judges by looking at the measurement data at various points on the small LED display panel, the operator immediately said: "No. "Although the image is too dark and inaccurate, there is still a whole light and shadow display basis. I probably know what color on the screen represents the percentage of printed dots, and I can use it. Once I take it away, I have to use my brains. There is no overall image with poor conversion. This phenomenon is to explain that the soft proofing using the additive color screen is not accurate, but the difference between the subtractive color and the printed matter can only be expected to reproduce the color in the future. Cognitive error. Even if you really use a proofing machine or digital proofing, this gap will still exist, but the tolerance and recognition of the gap between the buyers and sellers of printed materials will also be the basis for determining whether the business can continue. In general, soft proofing is used to see samples Customers can only rely on the reproduction quality of the printing factory. Wait a second, use ICC Profile for CMS color management, print output in the digital inkjet proofing machine of the printing company, and also prepare the same proofing machine in the remote client, and do the same color correction output, remote proofing of the two places is very feasible Yes, it is just the CMS color management calibration cycle, which cannot exceed two months. Piezo inkjet is the preferred model due to the high stability of the nozzle and the external temperature change. The hot bubble type will have larger fluctuations in the spray effect due to the condition of the nozzle and the temperature.
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