Some technical points to pay attention to plane scanner

With the continuous improvement of the technical performance of the flat-panel scanner and its advantages in terms of price, there are more and more users of the flat-panel scanner in the color desktop system. In order to meet the needs of the vast number of users, in recent years, the plane scanner has been divided into professional and general types according to different grades, specifications and applications. Understanding the various functions of the flatbed scanner allows the operator to smoothly scan out images of good quality. The following is a brief overview of the main functions and operating points of the flatbed scanner.

First, the choice of scanning methods

The scanning method of the plane scanner can be divided into two types: automatic and manual. These two different scanning methods will have different effects on image quality.

1. Automatic scanning

Automatic scanning refers to the "AI" function, also known as "fool" function. When the automatic mode is selected for scanning, the scanner will scan the image for the first time to identify the pixel distribution, the highest density, and the lowest density, so that the signals output by R, G, and B are adjusted by the computer and then processed. Official scan. For this reason, when scanning in the selected state, it should be noted that when setting the scanning range, the contents outside the screen should not be selected within the scanning frame. If the white border, black border, or cover other than the screen is also selected within the set scan range, the information content that does not belong to the original is already included in the screen. The automatic scanning software will make incorrect judgments on the original information, resulting in the automatic scanning software's main feature is to automatically find the black and white fields and calculate the contrast on the premise of the neutral gray balance setting, so that the image is scanned Can achieve copy and restore. Therefore, when using the automatic scanning function, it is necessary to notice whether the original has a color cast, whether the contrast is appropriate, and so on. Otherwise, image quality will not be optimal when scanning images using automatic functions.

2. Manual scanning

In most cases, we need to use the manual scan. This method can effectively adjust the color cast, contrast, and curve of the original so that it can better represent the level of a part of the original. When performing a manual status scan, there will be a series of dialog boxes that need to be set for each scan. Common scanners generally have the following settings.

(1) Settings for highlights and shadows

The setting of highlights and shadows is also called the setting of white field and black field. According to the scanning software set by the scanner, it can be roughly divided into the following three cases: black and white fields are printed in the state of C, M, Y, and K of the printing network. Calibration; Set the black and white fields with the brightness level appearing in the form of RGB. Normally set the white field between 170 and 255, the black field between 0 and 85; appear in the form of the original density, set the original minimum and maximum density To calibrate the white and black fields, some scanners are represented by digital levels in the form of bright and dark.

In the above highlight and dark setting, the printing dot RGB format is used for calibration. It can adjust the contrast and contrast of originals greatly; when scanning at the maximum and minimum density, the contrast will be adjusted on the basis of ensuring the original tone reduction.

(2) Curve and Camma settings

Curve state and gamma setting will involve the level of image scanning. Since the density of the transmitted documents, reflections, and printed materials are not the same, all the layers on the original must be copied on the printed matter so that the bright tone, intermediate tone, and dark tone are fully expressed on the paper, and the copying needs to be directed at different situations. Adjust the curve status. Because most of the software of the plane scanner can not only adjust the overall curve, but also can adjust the state of individual curves in the form of R, G, B. In this way, we can trim the ink's neutral gray balance and also process the overall color cast of the original.

Second, the print manuscript scan settings

In this top setting, there are generally four tops: 85 lpi (newspaper), 133 lpi (magazine), 150 lpi (general), and 175 lpi (sample). Since printed products are composed of outlets, recopying is based on the outlets of the existing outlets. At this time, interference patterns will be generated. When printing images with interference patterns, irregular patterns will be formed in the tones within the unit area, resulting in a grid pattern on the prints, commonly known as "rhizard." This setting of the flatbed scanner. Actually, the scanning focal length is adjusted so that the scanner cannot discern the dots of printed products. Therefore, when this setting is performed, the image sharpness will be affected to a certain extent. Among them, the thickest 85 lpi adjustment point of the dot is the largest, and the image is correspondingly blurred. The finest 175 lpi adjustment point of the dot is the smallest. Therefore, when it is not possible to determine the printed cable of a printed manuscript, in order to maintain the sharpness of the image as much as possible, scanning should be started from the selection of a finer cable setting until no "rhizard" appears.

Third, the setting of sharpness

What needs to be pointed out here is that sharpness does not equal sharpness. Although the sharpness increases, the visual effect improves the sharpness. On the other hand, excessive sharpness will make the image rough, especially when the original photo was printed with silver salt particles and prints. In the plane scanner. The sharpness of an image depends on the optical resolution of the scanner; sharpness creates a white and black border in the area between high and low density. Make it visually clearer. For such a computer-generated line, it will be determined by three factors: Amount, Radius, and Threshold. Some scanning software divides the sharpness into several levels, such as slight, medium, and stress. Under normal circumstances, the reversal film can choose a slightly higher sharpness, the photograph can choose medium sharpness, and the print can choose a slight sharpness. In addition, the performance of the manuscript, such as still life, landscape sharpness may be slightly higher. Characters, for example, can choose a lower tax setting.

Fourth, the image resolution settings

The resolution of the image should be set according to the net line of the final output film. In general, the image resolution should be set to 2 times the output cable. Such as: output 150lpi, image resolution should be 300dpi; output 175lpi, of course, the corresponding increase in image resolution. The higher the resolution is set. It may be better to reflect the corresponding level, but the amount of documents will also increase, which will greatly reduce the speed of scanning, transmission, and production of documents. Conversely, an image with too low resolution will greatly reduce the content it contains. Although the file size decreases and the file transfer and production speed increase, the output film will not match the output resolution of the film due to the image resolution. Mosaic phenomenon.

When performing a line scan, set the image resolution as normal. There will be a lot of sawtooth on the line turns and slashes. It's a lot of trouble for post-production. When the image resolution is increased to 1200 dpi, the sawtooth phenomenon will be greatly reduced. Of course, when the image resolution is increased, the scanning speed is reduced due to the increase in the amount of files. However, after the scan, in order to not affect the file transfer and production speed, the resolution of the file can be reduced to a normal state.

The work of each type of flatbed scanner is different, but their basic operation contents are generally consistent. The operator must fully understand the main operating functions, adjustment range, and performance ability. At the same time, he needs to understand the printing process and knowledge, and be familiar with the coloring rules of C, M, Y, and K. In order to better achieve satisfactory image quality.