Complete solution of the most popular pre printing

2022-08-12
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Complete solution of prepress technology cases (V)

what format is used for PS output image into? What format should we use to be transparent

the resolution of the image in PS is 300. Output it to me in TIFF format (not compressed) after merging, and then import it to CD

ask: 1. Will the effect be good

answer: 300dpi is OK

2. And what extent should I zoom in and out of these pictures on the CD? Does zooming in and out make gradients streaked

answer: try to reduce the zoom. It's not a big problem to zoom out. Zooming in more than 1.5 times will make the image quality worse. The larger it is, the more obvious it is.

3. What format should I use for transparent images

psd is better for transparent images in CD, but it can't rotate or flip, otherwise the layout will lose information.

the most important problem: when I process graphics in PS, I use CMYK mode. Will there be color changes when I output them in TIFF format? Will it change again after importing into CD

answer: there will be no change

what is color separation? Generally, I heard people say that the sample manuscript made by others should be separated before making film. What kind of process is this? Does the so-called color separation plot mean that the four channels of CMYK in Photoshop plot separately? Also, what's the story of using CDs to make films

answer: color separation is a printing professional term, which refers to the decomposition of various colors on the original into four primary colors: cyan (c), red (m), yellow (y), black (k); In computer printing design or graphic design image software, color separation is to convert the color mode of scanned images or images from other sources into CMYK mode. If you want to print, you must separate the colors into yellow, magenta, cyan and black, which is the requirement of printing. If the image color mode is RGB or lab, there may be only a little bit on version K when outputting. The color separation operation is actually very simple: you only need to convert the image color mode to CMYK mode. When outputting the film, the image will generate points according to the color channel data, and be divided into four color separation films: yellow, magenta, cyan and black

generally, check each color during output to correct whether it needs hollowing or embossing. Generally, the film is output in four colors: green (c), red (m), yellow (y) and black (k), each with a film. CD is a software for typesetting and drawing (full name: coreldraw8/9/10.0/11.0)

What does registration mean

because printing uses four color plates to realize color reproduction, the position of the four color plates can be accurately aligned by means of registration. In the design draft, you can make some crosshairs or crosshairs by yourself, and some software can automatically generate alignment marks on the four color plates

what is a line

line is the number of added lines. The unit of expression is LPI. For example, general line reporting can use 75~90 lines (75~90 LPI). 150~175 lines (150~175 LPI) for color offset printing. Because the previous points were linear, it is customary to call all the point encryption degrees as lines. To be precise, it is the accuracy (resolution) of the laser Imagesetter in interpreting digital files on the film. The so-called line refers to the sharpness of printing. What we design is the resolution, which represents the sharpness of the image. The relationship between line and resolution is: 1.5 times of line is equivalent to resolution (generally speaking)

basic knowledge of printing points

in the printing process, continuous and halftone images are adjusted by the density of points. By mixing the dots of CMYK four colors, you can show an infinite number of colors

at present, there are two different types of dots used in printing process: amplitude modulation dot (AM) and frequency modulation dot (FM)

am point

am point is the most widely used point at present. Its point density is fixed, and the depth of color is expressed by adjusting the size of points, so as to realize the transition of hue. In printing, the use of amplitude modulation points mainly needs to consider point size, point shape, point angle, line accuracy and other factors

dot size

dot size is determined by dot coverage, also known as inking rate. Generally, we like to use "Cheng" as the measurement unit. For example, points with a coverage of 10% are called "10% points", points with a coverage of 20% are called "20% points". In addition, points with a coverage of 0% are called "Jue", and points with a coverage of 100% are called "field"

the tone of printed matter is generally divided into three levels: bright tone, middle tone and dark tone. The point coverage of the bright part is about 10% - 30%; The point coverage of the intermediate adjustment part is 3: the abnormal pendulum orientation is about 40% - 60%; The dark part is 70% - 90%. The field part is divided separately

point shape

the point shape in printing is not just a single circle in your imagination. It can be divided into three types: square, round and diamond according to the shape of the point at 50% inking rate

square points form a checkerboard under 50% coverage. Its particles are relatively sharp and have a strong ability to express levels. It is suitable for the performance of lines, graphics and some hard tone images

circular dots are independent in both bright and middle tones, and only in dark tones can they be partially connected. Therefore, the performance of the mining level is poor, and four-color printing is rarely used

diamond dots integrate the hard and soft characteristics of square dots and circular dots. The color transition is natural and suitable for the performance of general images and photos

point angle

the selection of point angle plays a vital role in printing plate making. If you choose the wrong point angle, interference fringes will appear

the common point angles are 90 degrees, 15 degrees, 45 degrees and 75 degrees. The 45 degree point is the best, stable and not dull; The angle stability of 15 degrees and 75 degrees is worse, but the visual effect is not rigid; The angle of 90 degrees is the most stable, but the visual effect is too dull and aesthetic

when two or more points are set together, there will be mutual interference. When the interference is serious enough to affect the beauty of the image, the commonly known "moire" will appear

generally speaking, when the angle difference between the two points is 30 degrees and 60 degrees, the overall interference fringes are relatively beautiful; The second is the point angle difference of 45 degrees; When the angle difference between the two points is 15 degrees and 75 degrees, the interference fringes will damage the beauty of the image

number of dots and lines

the size of the number of lines determines the fineness of the image, which is similar to the resolution The common applications of line number are as follows:

line: low quality printing, posters, posters and other large-area printed materials that can be viewed from a distance, usually use paper and offset paper for printing, and sometimes use low gram sub powder paper and coated paper

150 line: this accuracy is generally used for ordinary four-color printing, and it is available for all kinds of paper

175-200 lines: exquisite picture books, pictorials, etc., most of which are printed on coated paper

250-300 lines: picture books with the highest requirements, etc., most of which are printed on high-grade coated paper and special paper

frequency modulation point

screen modulation point is a new addition method developed since the 1990s. It should be coated with grease when it is not installed with amplitude modulation point; The same is that the point size of the screen adjustment point is fixed, and it realizes the step adjustment by controlling the density of the points. The bright part is sparse, and the dark part is dense at May 24

how many points can be seen from the mirror

ten percent: three points of the same size are placed between the two diagonal points

20% points: two points of the same size are just placed between the two diagonal points

three percentage points: 1.5 points of the same size are just placed between the two diagonal points

fourfold: 1.25 points of the same size are just placed between the two diagonal points

50%: a point of the same size is just placed between the two diagonal points

10% corresponds to 90%. 20% corresponds to 80%. 30% corresponds to 70%. 40% corresponds to 60%. It's just that the size of the point is just opposite to the distance between them

(for a 300 resolution bitmap, we know that it refers to an image composed of 300 square pixel points per inch, horizontally and vertically. When the image is enlarged, it will be found that it is composed of countless points of different sizes. Because the printed matter is composed of points, the number of lines added to the printed image refers to the number of lines per inch in the horizontal or vertical direction of the printed matter, that is, the number of hanging lines. It is called the number of lines because the earliest printed matter has linear points. The number of hanging lines is a single number Bit is line/inch, which is called LPI for short. For example, 150lpi refers to 150 lines per inch. Add to the image, the larger the number of hanging eyes, the more the number, the denser the points, and the richer the hierarchical expressiveness. The larger the point, the darker the color and the darker the layer; The smaller the point is, the lighter the color is, and the brighter the level is. The line accuracy (LPI) does not correspond to the resolution (DPI) of 1:1. For example, pictures with 150 lines require a resolution of about 300dpi. The resolution is about twice the number of lines. If you don't pay attention to theory. It can be understood as the density of film or ink!)

intermediate color: the mixed color prepared by the mixing type of two primary colors is called intermediate color or secondary color, such as R, G, B, M80%, y70%, C20%, y80%, etc. Intermediate color is also called secondary color

compound color: the color produced by the mixing of primary color and intermediate color, or the mixing of two intermediate colors is called compound color or tertiary color. In fact, multicolor is a mixture of three primary colors, just a combination based on one primary color

complementary color: if the two colors are black after mixing, the two colors complement each other. The intermediate color formed by mixing any of the three primary colors with the other two primary colors is the complementary color. For example, m and G are complementary colors. If the two colored lights are mixed to form white, they are complementary to each other

what determines the trapping value? What is the difference between choke and spread? What does keep away mean

(1) the trapping control is carried out on the interface with two colors. The shrinkage of its foreground (or background) or the expansion of the core knowledge of Jinan assay horizontal tensile testing machine, and the procedures of hollowing out or making empty are called trapping values. In order to avoid the exposure of overlap, the trapping value should be slightly higher than the four-color registration accuracy of the printing machine. Due to the different printing processes, paper and printing machinery used in various color printing materials, the more precise the printing materials are, the higher the registration accuracy is, and the lower the trapping value is. The United States printing service and printing houses have published typical trapping values. For example: for sheet fed offset printing, the number of dots and lines of coated paper is 150lpi, and its trapping value is 0.08mm; For web offset printing, the number of lines added is 100lpi, and the trapping value is 0.15mm

(2) shrinkage is to increase the area of the (light) background, so that it can invade the darker foreground (text or figure) on the boundary, while maintaining the contour shape of the foreground

expansion is to increase the foreground area with lighter color, make it invade the background area with darker color appropriately on the boundary, and keep the shape of the background contour unchanged

(3) void is when the background is black and the foreground is hollowed out, it is necessary to void the three color versions of CMY so that the foreground outline is defined by the monochrome black version

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