As we all know, the scanner is an input device that converts analog manuscripts into digital images. Whether it is a resource for network transmission or a need for rich print content, the scanner plays a very important role. The popular scanners on the market today are flatbed scanners, roller scanners, and handheld scanners. Of course, they can be further subdivided. For the operation of the scanner, not only must the device be selected according to different types of originals, but the scan mode or storage mode must be correctly selected to improve the scan quality.
Different manuscript scanning options
Scanner scanners generally provide us with three scanning methods: black and white, grayscale, and color. The "black-and-white" method applies to black and white originals, while "grayscale" applies to graphic-text files, and colors are suitable for scanning color photos. The scanning method also directly affects the scanning speed and the size of the scanned document. Therefore, before the scanning, we should select an appropriate scanning method according to the scanned object, so as to obtain a better scanning effect.
1. Line map scanning
For the line draft, select the scanning color mode "LineArt", only need to consider the distinction between the black pixels and white pixels of the dividing line, scanning should pay attention to the threshold (Threshold) setting, that is, what color tones on the original document is swept into black, What has been swept white so that it retains enough detail in the brightest or darkest areas of the artwork. Normally, the threshold value = 50% is used as the standard value. If the test scan pattern is too dark, the threshold value is increased so that more gray edges can be converted to white pixels. If the test scan is too bright, reduce the threshold so that more gray edges can be converted to black pixels. Another issue to pay attention to is to determine the scanning resolution. The scanning resolution of linework should be higher than the scanning resolution of continuous tone images. Should be generally more than 600dpi to make the output line sawtooth is very small, the naked eye can not see clearly, the image resolution is too low, will produce jagged.
2. Grayscale scan
For some line text, you can also use 256 grayscale scans, the scanned image is smoother than the LineArt mode, and it is better to save the grayscale at some edges. After swept into Photoshop, you can adjust them according to the situation. To black. The original is color, and to obtain a grayscale image, to obtain a good level, it is best to use color scanning. Because the color map is highly saturated, the layers are rich. Such as using 256ShadesofGray may lose some information. After scanning in RGB mode and then in Photoshop to Gray, you can use the information of one channel to convert.
3. Scanning of color manuscripts
The color originals are of good quality, and it is only necessary to set correct parameters for scanning color originals. However, for a defective manuscript, the actual situation should be corrected during scanning. Special processing is required for some special originals, such as color pictures on color newspapers. The newsletter uses newsprint, so it differs from the art of coated printing. The density of newsprint blanks is about 0.15-0.2, which is equivalent to the sum of C: 3%, M: 4%, and Y: 10% of dots on coated paper, so newsprint is not white. Because newsprint is grayscale and paper is loose, ink is diffused, ink absorption is strong, and the reflectance of ink is low, even at a depth of 100% K, it is still not black (ie, the density is not enough). In short, the contrast of newsprint is only 1.2 or so, which determines that high-light areas should have small areas of C, M, Y, and K colors, and that the appropriate total overprint should be applied at the dark areas (not less than 250). To increase the contrast. In color newspapers, the level should not be reproduced as a key point. Primary colors and inter-colors should be used more frequently, and basic colors should be reused instead of using opposite colors or complementary colors to make the colors bright and lively. For the skin color part, the cyan plate should be used less in order to avoid graying and darkening, and the total amount of the three-color inks of C, M, and Y should also be reduced consciously.
4. Scanning of prints
Many prints have rose spots and mottles, and after scanning, rose spots and moiré are more pronounced.
In general, scanners have a de-networking function. The purpose of de-screening is to blur the image. You can remove the moiré and get a smooth image. Therefore, when encountering a printed document, the Descreen command is generally selected. Scanning to the Internet is better than scanning in Photoshop.
Some prints have very serious tortoises. Scanning go to the net still can't smooth the image. You need to continue to go to the net in Photoshop. Sometimes the image becomes too virtual after you go to the net. You can also use Unsharpmask to emphasize the sharpness in Photoshop.
5. Transmission of the scan
There are two kinds of transparencies: positive and negative. PositiveTransparency indicates positive and NegativeTransparency indicates negative. Flatbed scanners generally use transparent glass to hold the film in place. The light source illuminates the original from above the transparent glass. Normally, the glass can be scanned directly without refueling. The roller scanner is a method of wrapping oil on both sides of a document with a transparent film, and a document holder is used for squeezing out. The effect of negative and positive scanning is different. At present, the scanning effect of the scanner on the positive film is better than that of the negative film. Therefore, when selecting the original document, it is better to select the ideal positive film. It is better than the resolution of the reflection draft, rich in layers, and colorful. Fine particles, suitable for large magnification scans.
When scanning a transmissive original, cleaning the scanning roller and the stage can reduce the generation of Newton rings. But if it still exists, use a duster equipped with corn flour, away from the scanner, and squeeze the corn flour out of the duster so that it spreads out in the air. When the large particles fall, hold the translucent film. The corner of it, let it go through the dusting area, so that the fine particles of the air fall on it, you can achieve the purpose of eliminating the Newton ring.