How to get accurate printed ICC
The color card used by the ICC that commonly generates CMYK is IT8.7 / 3 or ECI2002. 1. Be sure to test the maximum density of the imagesetter when outputting IT8.73 files. The maximum density of the film output by the imagesetter must be guaranteed to be above 3.8! At the same time, it is required that in the IT8.73 chart range, the difference between the left and right densities is less than 0.05. Next, the linearity of the imagesetter is corrected to ensure that the output film linear error is less than 1%. Finally, the bottom ash of the film is strictly controlled, and the bottom ash value is required to be less than 0.04. 2. Correctly adjust the printing time and printing conditions, and pass the printing test strip: 2% of the dots are required to appear, 3% of the dots are intact, and the printing is guaranteed to be white for the level 3 gray ladder, and the level 4 gray is reserved, with conditions You can use the printing plate density meter to measure the loss after printing, it is best to ensure that 50% of the dots on the printing plate are not less than 45% 3. Determine the printing paper and ink. Generally, a printing factory will have different paper types and ink types. Different paper and ink will have different printing effects. You can do it separately, or you can choose the most representative copperplate paper and the most commonly used. Ink. 4. Determine the correct printing color sequence, usually the printing color sequence is arranged according to the viscosity of the ink, the most viscous ink is printed first, and it has the strongest adhesion to the paper, which can prevent the subsequent ink from removing it from the paper Peeling, the arrangement of modern four-color offset inks from strong to weak is KCMY, so our preferred color sequence is also the same, but since we know that the adhesion of ink on paper is not only a problem of ink itself, paper is also a The deciding factor, the acidity and alkalinity of the paper are also directly related to the drying and adhesion problems of the ink, and because the viscosity of C and M is relatively close, the paper will have a greater impact on it. If an overprint failure occurs in the two colors of CM , Then you must consider replacing the printing color sequence that is more suitable for this kind of paper, such as KMCY arrangement. The first task of printing is the restoration of dots, then a good print should be judged from the following aspects: 1, the best dot shape, 2, the maximum amount of ink received by the paper, 3, the maximum density of the four colors on the spot , 4, the smallest dot expansion, 5, the best gray balance performance, 6, accurate overprint accuracy. To judge these points, the chief of the printing press told you that it is useless, so before standard printing, we will let the machine print a test chart (see below) to judge the status of the printing machine: This test chart has the judgment criteria for the six points mentioned above. Next, we will explain how to judge whether the printing press is in the standard state according to this figure, and the most important point: to establish a color printing of the printing press. Standard! [next] First, the shape of the dots. The printing process is basically a process of dot copying. All colors are restored through the dots. Then it is the ultimate goal of printing to ensure that the dots on the film are most accurately restored on paper. Of course, we must know that the ink is transferred through the blanket and pressure. Under the effect of pressure, the ink on the dots will squeeze and cause the shape of the ink dots on the paper to expand and deform. This is the objective existence of offset printing. While we understand this objective fact, we try our best to control and stabilize this change is the fundamental purpose of our standardization of printing presses. In addition to visual observation with a magnifying glass, there are some special pictures on the test chart to let us make a correct judgment: the leftmost and rightmost image in the picture is to judge whether the printing machine has dot deformation in the horizontal and vertical directions. (See below) From the partial enlarged view, we can see that there is a vertical stripe and horizontal stripe area: now you can use the density meter to measure the density value of the vertical stripe area and the horizontal stripe area, when the density of the vertical stripe area is greater than the horizontal stripe area, it means that the machine is on the left and right. The dot deformation occurs in the direction, otherwise the machine deforms in the up and down direction. Of course, without a density meter, you can also use the naked eye to distinguish the color depth of the two areas. Through the observation and adjustment of these four color groups, in short, there should be no difference in the density of the two horizontal and vertical stripe areas. After this adjustment, we use a 50x magnifying glass to observe the shape of the dots at 60% of the dots on the test chart: It is required that the dots are full and connected into four corners of a diamond shape. The 50% dots are not observed because after the printing, the four corners of the 50% dots will be lost due to exposure and will not be connected. [next] Second, the maximum ink receiving amount of the paper: the maximum ink receiving amount of the paper is related to the dark level of the printed matter and the saturation of the ink layer of the printed matter, and is also the most important guarantee method for the color space of the dark part of the printed matter. In the case of not drying, the larger the maximum ink amount of the paper, the better. We can judge from the figure in the following area: We first find the maximum black ink level in the vertical direction. We can use the naked eye and the instrument to find the density and level of the black level ink level that just happened, such as 92%, and then compare the density and level in this column. For example, the density of 358 and 347 are the same, but the density of 336 becomes smaller, so 347 is the maximum ink volume we want, so we can use the black plate density = 92, the maximum ink volume = 347 as the maximum black plate ink volume of our printing machine and The maximum total ink amount of the paper, the maximum total ink amount and the maximum black ink amount are also an important parameter to be used later when we want to generate the ICC characteristic curve! Of course, the maximum ink volume is also subject to a big constraint is the drying speed of the ink on the paper. Too much ink volume will bring difficulty to the printing press, such as printing failures such as dragging and ink! Third and fourth, the maximum density in the field, the minimum expansion of the dots, and the best performance of the gray balance. These three points are related to each other and are related to each other. Here we discuss them together. First of all, one of our important principles is Under the condition of ensuring the best gray balance, the smallest dot expansion rate is obtained and the maximum field density is determined. Among the four colors, the black version is considered independently: we first need to determine the black version density, because the other 3 colors The density and gray balance are interrelated and based on the gray level of the black version as the gray balance, let's look at an area in the test chart: In modern offset printing, we require the density of the black version to be as high as possible, but due to the water-ink balance of the printing press; too thick ink layer thickness will bring about the adhesion of the ink is what we often say is the paste version, because the black ink has the highest viscosity, it The possibility of pasting is the greatest. In the above picture, we require the thinner anti-white lines in the image to be as clear as possible. Increase the amount of black ink until the 0.01 point line is just pasting, the solid density of the black version at this time can be Think that the largest density is the best, we need to look at the dot expansion linear graph: (below) We visually require that the gradient of black ink is uniformly without steps, and the darkest part does not have a paste version. For the black version, we can appropriately increase the dot expansion rate of it, in order to obtain a darker black, so 50% is required The expansion of the dots does not exceed 15%, that is, the measured value is below 65%. After the above conditions are generally met, measuring the density of the black version is the maximum black density we want to set, generally around 1.7-1.9. After we decided on the black version, we decided to determine the maximum density of the other three colors: Fifth, the best gray balance, here are mainly two gray bars, the upper gray bar is 3 colors (CMY) gray, and the lower one is the gray with monochrome black at 50%. Now we require three colors to be adjusted during printing Density, until the upper and lower two grays are very close in terms of hue and lightness. After the two grays are close, we are measuring the dot expansion of the three colors of CMY at 50%. It is required that the dot expansion rate be less than 12%. That is, less than 62%, and observe the gradient of the three colors at the same time. Like the black version, the gradient is required to be symmetrical and stepless. At this time, the solid density values ​​of the three colors are recorded, and they are used as the maximum density. The density range is: C = 1.5-1.65, M = 1.4-1.55, Y = 1.2-1.4, there is another area on the test chart to check the gray balance. It mainly checks the gray balance at different levels: The above figure shows the ratio of the three colors (CMY) composed of gray at different levels (respectively 7%, 30%, 60%, 80%). We found the color blocks with the best gray balance, the so-called best gray Balance is required to be consistent with the gray color of the same tone as the monochrome black version. As long as the three-color gray block is closer to the red diagonal line in the figure, the gray balance of the entire printing is more standard. Now we have the maximum of four inks Density value, maximum black ink volume and maximum total ink volume Sixth: Overprint accuracy. Overprint accuracy is the most basic requirement for printing, but it is also a very important factor in our color management. To be a color standard, the accuracy of color is very important. The four colors of offset printing The dots are arranged at a certain angle. When the overprint between the color plates fails, it will seriously affect the color rendering of the printed products. Therefore, there are many places in the test chart to provide us with a check of the accuracy of overprint: In the above picture, we require that no two white edges can appear in any direction. So far we have basically adjusted our printing machine or we can say that we have completed the standard adjustment of the printing machine. There are still some photographs in the test picture that can be used to observe the actual effect after adjustment. These pictures have certain representatives Sex: There are dark-tone photos that reflect the levels of the dark parts; high-key photos that reflect the levels of the bright parts, and landscape figures, etc. You can judge the correctness of these photos based on your own experience. Next, we can use these printed standard data to guide the printing of our standard color target files. [next] Now we enter the main task: guide us to print the standard color target file according to the above printing standard, first select our color target, generally speaking, we can print IT8.73, or print ECI2002 if it is based on other ICC It is recommended to print IT8.73 files for color management. Too many color blocks are not a good thing for digital proofing based on ICC characteristic files! Things to note: 1. To determine the arrangement of color targets according to your measurement tools, different measuring instruments have their own color block arrangement, porfilemaker provides these different arrangement of map files. Measurement: There are a lot of measurement tools and software. Experts who are skilled in using these tools and software are more here. I will not repeat them. I generally use profilemaker + lino / scan to measure, printopen to check, and profilemaker to generate ICC The point I want to talk about is the verification of the measured data and the setting problem when generating the ICC characteristic file. These two points are easily overlooked. Let ’s first check the verification. Is the printed color draft certain? Standard? Is it consistent with the printing standards we expect to develop? This requires us to make a judgment on the measured data. After the measurement, do not rush to generate ICC, but save its measurement data as a TXT data file. Here is a very useful function in printopen, which is used to check the measurement Data: We open printopen, click to create a new curve, then click to open a data file, select the TXT file generated by our previous measurement, see the figure below. After opening, we can first see if its color gamut range is normal: Next, focus on the expanded curve of the measured dots: The above figure should check whether the network expansion is within our ideal range? Does the maximum expansion of each color curve dot occur at 50%? Is the parabola smooth? Wait, if there is a problem, we can manually measure the standard printed sheet to determine whether the problem is on the measurement or printing. In short, before generating the curve, we must make the data obtained is accurate, not with defects, only established in The ICC characteristic curve based on the correct data is valuable! Eighth, the final generation: After the data examined by the appeal, we then transferred to the profilemaker and started to generate the ICC curve. Here we should pay special attention to the setting of the color separation method, which will be related to the application of ICC in the future. Not just for digital proofing, it will be the essence of our color management system! It also guides our screen soft proofing and color matching! Let's take a look at the picture below, the color separation settings at the time of generation in profilemaker: First: UCR or GCR? This depends on the type of your picture. Generally speaking, UCR allows a small amount of black version to participate in color separation. If you want to copy a color picture, you have to choose UCR, which can make your picture more pure. High, such as the color of the character, we try not to let the black version intervene. Undoubtedly, UCR should be our first choice. Here I suggest that you use GCR to generate another ICC. The reason is that when you do some black and white tone-based works, the intervention of more black editions can allow you to ensure the consistency of the color tone when printing, like black and white with warm and cold tone. Photos, Chinese paintings, etc. must be separated by GCR color separation method. Then we have to enter your maximum black ink volume and your maximum total ink volume according to the characteristics of your printing press. The total ink volume of c, m, y, k is also based on the data on the printed measurement chart! Fabric Sectional Sofa,Home Theater Recliner,Furniture Fabric Sofa,Fabric Recliner Sofa Chair Kaifeng Lanwei Smart Home Co., Ltd , https://www.sofa-recliner.com
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2. Pay attention to the placement of the picture on the printing plate, and put it in the center as much as possible while avoiding the pause position of the ink stick of the printing press. The new printing machine can easily adjust the stay position of the ink stick in the operation window. The adjustment of some old models is very troublesome.
3. It is necessary to register accurately when printing, the importance of which has been mentioned above.
4. It is also necessary to print strictly according to the color density determined after the previous test (assuming that the solid density of the four colors we set earlier is K = 1.9, C = 1.6, M = 1.55, Y = 1.4), then when printing The error should not exceed 0.05 of this standard density.
5. In the entire color target range, the density error of the same color should not exceed 0.05! (Assuming the C color density standard = 1.6 then the C color density must be controlled between 1.55-1.65 in the entire color target range! Remember this is very important !!!)
6. After adjusting the machine and color, let the machine open more than 200 sheets all the way, take the last 10 sheets, and measure the density value respectively to select the printing product closest to the standard density value.
7. OK, at this point you finally got a color draft of the standard printing press color characteristics.
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