Image processing skills in newspaper printing
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Pictures play an important role in the newspaper layout. If used properly, not only can beautify the layout, increase people's interest in reading, but also play a finishing touch. The processing of a picture before printing directly affects the effect after printing. Therefore, through years of practice, we have made some useful explorations on image processing.
Before scanning a picture, you should first review it. For the quality of the picture, it should be done in mind, that is, whether the exposure of the picture is excessive or insufficient, and it is not necessary to go to the network, so that the picture can be properly processed during the scanning process, because the picture is processed during the scanning process. The level of loss is the least.
The general picture is scanned in color. If it is a grayscale image, it will be better to use a color scan. The grayscale image converted from color is more layered than the grayscale image scanned directly, especially for colors with a saturation of 70% or more. There is a "dash" option on the finished linocolorelite setting panel. If it is a print, you need to select the value here. The higher the printing accuracy, the larger the number of pictures to be selected. In addition, 6 options such as “color calibration” can be selected as default, and can be selected according to your own situation. The "Color Assistant" in "Calibration" is a very useful tool. Choose a different method for the picture, or freely determine the selected value. Adjusting the data during the image scanning process will retain more layers and details.
In photoshop processing pictures, we must first determine the black and white field and gray balance of the picture. These two factors are very important and necessary. The determination of the black and white field is not the same according to different printing needs. But the standard is that the black field can't be ruined. However, in order to ensure the visual effect of the picture after printing, it is possible to consider a small area of the net or paste, but it must not be a large area. If the picture is distorted, we can restore its color by gray balance, but the moderate gray affects the color of the whole picture, so it should be accurate when used. The mastery of gray balance has the following experience, that is, below 20% or above 80%, the value of cmy is basically equal; in the middle value part, the value of my is basically the same, but the value of c is 10% to 15% more than the value of my.
In actual operation, the processing of grayscale images will be relatively simple. There are two ways to exchange color images into grayscale images: directly convert them with the “mode” function; or convert the color images into lab mode first, then delete “a channel” and “b channel”, and finally convert the image into & "Grayscale". In the chroma lab mode conversion, the luminance l channel retains more layer changes, so the effect will be better. After the grayscale picture is fixed in the black and white field, it is necessary to pay attention to the level of the picture. The middle tone must be opened. Otherwise, the picture will have a misty feeling, dirty and unclear, and the contrast of the middle tone will increase, which will obviously improve. This situation.
In the process of using Photoshop to process images, don't let the images turn around in both modes. Because each time a conversion is made, part of the original picture details will be lost. When converting rgb mode images into cmyk mode images, the color separation parameters will play a decisive role in the effect of image conversion. The adjustment of the color separation parameters will greatly affect the conversion of the picture. The photoshop image processing software has the ability to control the color separation parameters. That is to say, when it is necessary to convert the image processed in the rgb mode into the cmyk mode for output, the adjustment of the color separation parameter can be alleviated in the picture during the conversion process. The color is lost when the mode is switched.
If the rgb mode picture is converted to cmyk mode, an intermediate step is added to the operation step, that is, first converted to the lab mode. The lab mode consists of three channels, the l channel represents the brightness, which controls the brightness and contrast of the picture, and the a channel includes colors from dark green (low brightness value) to gray (middle brightness value) to bright pink (high brightness value). The b channel includes colors ranging from bright blue (low luminance value) to gray to focal yellow (high luminance value).
The lab mode is similar to the rgb mode, and the blending of colors produces a brighter color. Only the value of the luminance channel affects the light and dark variations of the color. The lab mode can be thought of as a mode of two channels of rgb mode plus one luminance channel. The lab mode is device-independent and can be used to edit any image (including grayscale images) and is as fast as the rgb mode, several times faster than the cmyk mode. The lab mode ensures that there is no loss of color in the cmyk range when performing color mode conversion.
Processing images in different modes will have different effects. Like lab mode, it is helpful to increase the contrast of the image, but the amplitude is not too large, otherwise the image will be distorted. Rgb is the best mode for processing images, providing photos with saturation and brightness, performance levels and other functions are very good, especially good at adjusting people's facial color, without causing distortion or loss of level. Only all pictures are converted to cmyk mode before printing, so there is an advantage in adjusting the picture in cmyk mode. In this mode, adjusting the colors through the channel can prevent the picture from being color cast, which is also very convenient for determining the black and white field.
Different pictures require different processing methods. Pictures like Chinese paintings must be faithful to the original film, and the color cannot be changed because the effect is good. Pictures such as comics and calligraphy can be considered with bitmaps in order to ensure that the details are not lost. This is clear and the image capacity is small, which will increase the speed of the hairline.
In addition, there are many useful tools in Photoshop "Image One Adjustment", such as "Brightness/Contrast", "Hue/Saturation", "Optional Color", etc. In actual work, as long as it is used reasonably, it will get very good. effect.