Take advantage of the scanner's best performance—original correction function

Most operators use the scanner to scan the image, adjusting only the resolution and scaling options, and the rest use the default settings. Practice has proved that this does not give the best scanning results. In particular, when the original image is defective, the scan results are even less ideal. When scanning a defective image, how can you take advantage of the scanner's best performance and sweep out higher quality images? This requires careful analysis of the original condition, making full use of some original correction functions provided by the scanner and carefully adjusting the scanner's default settings.

First, the exposure of the picture is not allowed

Brightness and contrast are adjusted during scanning, and overexposed images look white because the brightness is too high; underexposed images look dark because the brightness is too low. At the same time, the images lack levels and the details are not rich. At this time, we can drag the sliders on the brightness and contrast sliders to make the image brightness moderate and the contrast suitable. Since brightness and contrast adjustments work on all pixels in the image, care should be taken in adjusting them. For example, the main information of a picture is in a dark area, making it brighter to make details more visible. However, if you use the brightness adjustment function to brighten all areas, you will lose all the details in the brighter area.

Second, color cast pictures

Adjust the color balance when scanning, if the image is somewhat color cast, you can use the color balance option to change the overall tone of the image. When the color cast is not serious, you can select the "Automatic Color Balance" option and let the software automatically correct. If the color cast is serious, you must manually adjust it. The color of the scanner is mainly a mixture of red, green, and blue colors. The scanner provides adjustment functions for each of the three basic colors. The adjustment options include three sliders: red, green, and blue. To adjust the image color, simply drag the slider on the slider to the color you want to add to the image, or drag the slider away from the color you want to reduce. To make color adjustments, you need to master some chromatic knowledge, especially the principle of complementary colors: two colors that are in relative positions on the color wheel are called a pair of complementary colors, such as red and cyan, green and magenta, and blue and yellow. Complementary colors. The so-called complementarity is the reduction of a color in an image, which inevitably leads to the increase of its complementary color. It is absolutely impossible for a color and its complementary color to increase or decrease at the same time.

Third, the lack of hierarchy of pictures

The gamma value is adjusted during scanning. The gamma value affects the tone of the middle value of the graph or the gray level of the middle level. By adjusting the gamma value, the brightness value of the midtone grayscale of the image can be changed to increase the intermediate level of the image, without having too much influence on the dark and light levels. Entering a larger number will increase the range of midtones. This will result in less contrast and more detail in the image where the midtones account for a large proportion of the image. Entering a smaller number will reduce the range of midtones. Doing so will increase the contrast of the image and reduce the details of the image. When the curve moves down, the corresponding pixels of the image darken; when it moves up, the corresponding pixels light up. Its adjustments often need to be used together with brightness and contrast to achieve satisfactory results.

Fourth, the composition of the picture is not ideal

Scanning should be carried out with a reasonable cut. Pictures with inappropriate pictures often have a cluttered background, unobtrusive subjects, or skewed scenery and poor visual effects. During the scanning, the original image may be selected by selecting the scanning range as required, and the skewed image may be corrected for artistic re-creation. The specific operation is to select "scan size" as "user-defined" mode in the scan setting options, and then select the area to be scanned by dragging the selection box in the preview image window. To do this, hold the left mouse button down at the corner of the area to be scanned, drag the marquee to the opposite corner of the scan area, and release the left button. In this way, the scanner will automatically scan only the selected area. Pictures with skewed scenery can be corrected by using the "rotate" function.

Fifth, the printed picture

The use of the descreening function is used during the scanning process. The printing field uses the hanging screen printing technology. It depends on numerous small and large dots to represent the brightness of the image. These dots are acceptable to the naked eye, but they are a non-negligible problem for the scanner because the scanner scans the printed photos and scans them to affect the quality of the image. The de-networking technique can be used to analyze the images of the outlets and restore them to originals without dots to reproduce the original picture. Scanners generally have several options for us to choose. When the original image is a magazine or a laminated print, please select “magazine”; when the original image is a newspaper or a relatively coarse dot print, please select “newspaper”; when the original image is a high-quality fine print and the outlets are very small, Please select "art print". It should be noted that if you are scanning non-printing materials, you must select "Do not set" and do not turn this feature on because it will reduce the quality of the scanned image.

By modifying the scanning parameters, it is possible to make up for some deficiencies of the original image during scanning, and appropriately improve the scanning effect, but the effect is always limited. The best way to get the ideal scan is to choose a good picture.

VI. Pictures downloaded from the Internet

Since most pictures downloaded on the Internet are in RGB mode and the color range of RGB mode is larger than CMYK mode, in order to ensure the printing effect of images, it is better to use RGB mode for processing, and finally convert to CMYK mode. When editing images in RGB mode in photoshop, select the CMYK preview option in the View menu. That is, edit images in RGB mode and display images in CMYK mode. Most of the downloaded images are small in size due to their display size. When we want to make images needed by newspapers, the images will become unclear. If there is a mosaic, it is even more important to note that when sharpening, it is not possible to sharpen too much. If the original image is a color image but is to be used in a grayscale layout, do not edit the original image directly to grayscale mode when processing. The RGB mode should be used for processing. The processed image is first converted into an L*a*b* mode image, and then the L* channel image is selected as a grayscale image for printing through the channel separation command. Note that do not convert between the RGB and CMYK modes, not to transfer the two modes, because in the bitmap image editing software, every time the image color space conversion, will lose part of the original image details information.

Note on the processing of newsprint printed images: In order to make the colors bright and appropriate to aggravate the main colors, reduce or not use the opposite colors appropriately; properly leave off the dark tone to protect the medium and bright tone; the figures of the black and white image of the character cannot be too high. To avoid being too dark, bright tone should be enough to do enough.

In short, for the scanning and production of images in prepress systems, they all have deep knowledge and experience. Therefore, the operator of the prepress system must be able to grasp the various techniques of image processing, enhance their own aesthetics, accurately determine the quality of the picture, and really get a good picture printing effect, or do not be afraid of trouble, carefully and carefully adjust, and strive to achieve The processed image has a higher quality than the original.

Source: Henan Graphic Arts