Description of printing parameters of the hottest

2022-08-23
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Snap -- description of printing parameters of paper advertisements (III)

Photography

different from general photographic display, photography and image capture used in the reproduction process require a full understanding of each process flow. How to get the best results will be described below

image capture and selection

if a high-quality image is not selected at the beginning, it is impossible to copy high-quality prints on the printing press. Using human eyes, photographic film and digital camera CCD array can capture a wide range of tones, which is much larger than the tone range reproduced by any printing process. The following are some guidelines for selecting images for the cold set reproduction process:

photographers should try their best to obtain the middle tone of key elements in the image, because cold set printing can only reproduce images with a density of 1.20. Dark areas are easy to blur or "become solid", while bright areas are easy to disappear or become virtual

the details of dark areas should be clear enough, and the percentage of points should be between 70% and 80%

the details of the highlighted area should also be clear enough, and the percentage of points should be between 5% and 10%

the highlight and dark areas recorded on the film or digital file will be compressed in the subsequent process, so it is important to agree on important details in the image before shooting. In the process of compressing the image before printing, the image should be highlighted to protect the details of the highlight or dark areas

although the transparent manuscript of the photo looks flat in level of detail, it is the best effect for printing

f/stop (shutter speed/aperture)

selecting aggregate exposure with 1/2 aperture smaller than the ideal measurement reading will help to improve the color reproduction effect, and do not overexpose the image. Generally, the density range of the image captured by the photographer on the transparent negative should not exceed the exposure of 2 to 3 apertures. The density range refers to the density difference between the brightest and darkest areas in the picture

the photographer uses the term "f/stop" to indicate the light intensity. One "f/stop" is equivalent to a reflection density of 0.30. Copy density A transparent manuscript with 6.8 "f/stop" is equivalent to 6.8 in the density range × Printed on film with 0.3=2.04

in the cold set printing process, the density of the paper itself is generally 0.25, realizing the whole process of the impact experiment on the pipe. The density range printed on this paper is 1.0 (the maximum density of the cold set black ink is 1.25, minus the density of the paper 0.25). It can be seen that the density range of transparent originals (2.04) is larger than that of cold set printing. Therefore, in the process of prepress preparation, it is necessary to compress the hue range by some algorithm to adapt to the difference of density range

however, if the photographer only uses the light intensity of 2f/stop to capture the image, the density range of the transparent original is about 1.02. (in the process of film development, the contrast will increase. The increment of contrast varies from film to film. In order to judge the effect of the increased contrast, the film manufacturer provides the index of film gamma value. The photographer can adjust and obtain the required contrast increment with the help of the gamma value. The camera f/stop multiplied by the film gamma value will represent the density of the film after development. For example, the gamma value of a film is 1.7, while the single lens reflects light Type viewfinder measuring instrument measures the light intensity of an image with 2f/stop, so the film density range after exposure and development is 1.7*2, or 3.4f/stop. Each f/stop is equivalent to a reflection density of 0.30, so 3.4f/stop will result in a total density of 1.02.) Therefore, the photographer no longer needs to compress the hue to copy all the hues in the transparent manuscript, but can maintain the control of image reproduction

if the photographer wants to print an image without details of dark tones or highlights, he can expand the range of f/stop from 2 to 3f/stop. Testing and communication are the key to success. Craft refers to that the instructor must communicate with the photographer about the key areas of the image. Photographers must warn advertisers and prepress specialists that the final appearance of important images may change, so they must deal with these key areas in different ways

total range

if the photographer does not indicate the specific f/stop value, you can try to capture the full tone, that is, from light to black, including reflected highlights (bright surface emission, also known as no detail white). An original with a full tone range can significantly improve the contrast of the printed matter, because the image halftone in the detail free white area is no longer required in the color separation process. Scanning in this case will improve the effect of the whole range of prints, from paper whiteness to the maximum ink TAC density. An original with too high contrast will look attractive, but too high contrast is harmful to printed copies. In the process of color separation, details will be lost due to tone compression. Over copied originals usually have too high contrast

lighting

correct object forward lighting will help, and the preparation scheme still needs to be refined to improve the details of printed matter and help maintain the fidelity of color. This lighting method helps to locate the object in front of the lighting lamp, and obtain more recognizable details in the printing area by reproducing the details of the dark areas of the text and text. Using unified lighting during the whole process of photography will get the best reproduction effect, and can also maximize the details in all tone ranges of the text. We do not recommend using backlight, because backlight will cause the replication effect to darken and dirty

if the lighting of each element in the photo is not uniform and balanced, it will lead to difficulties in scanning. Because the scanner cannot maximize the details of light and dark areas at the same time

it is not difficult to illuminate from the back of the object. The goal is to make the background contrast with the object, so as to better emphasize the object itself. The unlighted background will turn dark gray or black after scanning and copying, adding a sense of image depth

sharpness and sharpness

when selecting a photo, the process director and artist should use a small glass magnifying glass or projector to carefully examine the original or transparent, and determine the level of image sharpness. Copy a clear photo. If you use indoor equipment, you can use flash and small camera lens aperture equipment. Such a combination can improve the focus and depth of field effect

using copies of photos, fast films and photos with enlarged particles will reduce the sharpness that could have been achieved in the printing process

such photos will also have a bad impact on scanning, because sensitive scanner optics cannot distinguish the "pixelated" particle effect. When making an excessively large enlarged image or selectively cutting an image, it is best to use an original with a large format (/4 or 4 × 5 inches), generally speaking, the larger the original, the higher the clarity of the final copy

spot and haze are the main reasons for the loss of color saturation of the original photo. During the exposure process, the flare non image light penetrating the camera lens will reduce and destroy the color saturation of the image. Background, strobe lighting and camera angle will all lead to the increase of light spots. In order to prevent non imaging light from penetrating the camera lens, photographers use filters, light shields, lens angles, high assurance projection grids, and objective lens shades. Mist is a natural weather condition associated with foggy and cloudy weather. Like light spots, mist often reduces the brightness of colors. The degree of reduction is determined by the camera angle and the amount of fog

background contrast/color

background contrast in the studio plays a key role in successful newspaper printing. White or highly reflective background will affect the exposure time of photographic film to record the light absorption details of main objects. If not carefully controlled, it will lead to redundant light spots, loss of detail and reduction of saturation. For example, when taking pictures of dark brown or black objects on a white background, details are often lost. The stillness that can increase contrast but not high reflection will improve the quality of printed copies

design guide

typesetting and lines

due to the close connection between China's extruder products and strategic new industries

for any printing, the selection and emission of lines and words are very important. When dealing with lines and words, consider the following criteria:

readability, including writing style, font (whether western language has serif), legibility of information to be printed and other factors

legibility affects the speed and accuracy of readers' font recognition. Legibility is determined by the characteristics of typesetting, such as font, font size, word spacing, line length, line spacing, paper color, ink density and other factors

printability describes the printing efficiency of a piece of paper. If printability decreases due to process factors, including original design, font selection and other factors, printing production time will be extended, waste and additional costs will be increased

profitability is usually used to judge whether a printing is successful or not. Money will be won or lost at any step in the whole production chain, from advertisers to suppliers. The selection and placement of fonts and lines will have a great impact on profitability

here are some guidelines to improve the quality and efficiency of reproduction:

thin lines and small fonts

lines and small fonts with four dots or thinner can only be printed in one color. The definition of small font is:

sans serif, 7 points or less

with serif, 12 points or less

fine serif, such as Bodoni font, 14 points or less

sans serif font is the best choice for cold set replication process

anti white lines and anti white words

fonts less than 12 points should not be reversed under the four-color background if it is required to take more complex parameters, and fonts less than 10 points should not even be reversed under the monochrome background; Serif fonts and fine serif fonts should not be reversed when they are less than 12 o'clock. Even if the font with larger size is reversed, it should also be tested to confirm whether the serif can be printed

in order to obtain satisfactory contrast and readability, in any monochrome, two-color, three color or four-color printing, inverted fonts cannot be placed in less than 70% of the plus area, and inverted White words cannot be printed on yellow or other light colors

add words

when printing text with a dot percentage of a field color, you should avoid choosing fonts with serifs or small, medium font sizes. Generally, the text reproduction effect with an increase of 80% or more is similar to that in the field. Before attempting to add text with a smaller percentage of dots, the legibility of the text must be considered

overprint and color

in order to ensure the readability of the overprinted text or lines under the colored background, the percentage of dots on the colored background should not exceed 25%. At the same time, the point enlargement/hue value increase (TVI) of various primary colors or mixed colors should also be considered. The effect of these flat tones reproduced on the printing machine is deeper than that obtained by the display and most proofing systems. When magenta or yellow is used as the background, the percentage of color value may be higher. Before creating documents and films, you should consult the newspaper or printing house about the film or document manuscript. The background should not be destroyed in the area of 12 points or less. For thicker text or title words, the background color should be used behind the black text to fill the trap, so as to avoid inaccurate overprint and perspective of the background color

image trapping/extension and contraction

image trapping should reach 0.005 inch or

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