The quality of the picture scanning determines the final quality of the picture, how to get the best quality of the picture, is a long-term common question in the industry. The quality of scanning has a great relationship with the scanner, scanning software and the actual experience of the operator. The control quality is nothing more than the original manuscript, scanning equipment, scanning parameter Settings and scanning technology skills. Below, I will talk about several aspects that affect the quality of scanning combined with my work practice.

1. Type of manuscript and analysis of manuscript

1. Color reproduction of the original requirements

① High definition. It is the basis of recording scene price adjustment, color, texture, three-dimensional sense, perspective sense, etc. ② Density contrast. The density contrast of the manuscript must be normal. It is generally required that the original contrast is between 1.8 and 4.0, and this kind of original screen has rich levels of bright tone, middle tone and dark tone, and normal distribution of coordination levels. Good color saturation, realistic texture (if the dark layer is rich; The level of medium charge and modulation is less, and the level of dark tone and middle tone of pressure level must be opened during scanning. ③ Color saturation. Check the manuscript under the standard light source (50O0K), the color saturation is the true response to the wave photography, only the manuscript with high color saturation can be the original with normal tone; (4) Image particles. The graininess of the manuscript affects the color, level, and texture. The fine granularity of the original manuscript facilitates the reproduction of layers and tones (especially the light tone texture) and the true expression of colors.

2. The original manuscript is usually divided into transmission manuscript, reflection manuscript and secondary manuscript.

Secondary originals: scoured products; The density range is small, the level is not rich, generally only the original large scan, should not be amplified. Usually good quality secondary manuscript density range is only about 0 to 1.6. It is far less than the density recognition ability of the scanner, and the scanning of such manuscripts can only be done by ordinary flatbed scanners. The secondary original often has the problem of color deviation, which needs to be properly corrected during scanning. Need to be reminded that scanning the second manuscript must be done to the net processing.

Reflection draft: ① photos. The density range of high-quality photos is only O ~ 2.2, which basically meets the requirements of prepress processing and printability; It is the most common manuscript in our daily work. ② Physical objects.

Transmission draft: ① negative film. Usually do not scan the negative directly, it is best to develop the negative into a photo and then scan. That's because, number one, negative films don't work. Not easy to restore color; Second, the negative film base has a layer of colored light film, which will cause the negative film to have no white field and is not easy to calibrate. ② Positive film (slide). It is produced by turning negative films, such as Slide 135. Its film base is not as good as the reverse film, the density range is small (0 ~ 2.8), and the particles are rough, the scanned image is also relatively dirty, its magnification can generally only be controlled at 4 to 7 times, and then large, the picture will be distorted. ③ Reverse film, also known as positive negatives, the negative material used in it and the development process are different from negative and positive, the quality is the best in the original, the safety range is between 0 and 3.8, and the scanning can be amplified more than ten times, which is the most ideal original.

3. Analysis manuscript

2. Scanning preparation

1. Warm up. The scanner needs a few minutes to warm up. Power on the scanner 30 minutes before you start scanning.

2. Clean and maintain the scanner regularly. Clean and maintain your scanner regularly according to the scanner's instructions. When the scanner is not in use, use a dust seal to cover it, and do not make the scanner doused with water.

3. Wash your hands before scanning to avoid fingerprint contamination of the scanned image. Do not use your mouth to blow dirt and dust on the glass of the scanning platform.

4. Clean the surface of the object or image being scanned. Air bags can be used to blow, depending on the object to be scanned can also be cleaned with water on its surface, but to avoid damage to the object, especially be careful not to leave scratches on the surface of the photo and film. Some original works of art should be protected when cleaning.

5. Flatten the manuscript. If the software is used to correct the marks caused by the curl of the manuscript. It will reduce the sharpness and quality of the image. Although there are many features in Photoshop (such as blurring and sharpening methods) to process images, this is not the best way to solve the defects in scanned images.

6. Approved. Using calibration software can adjust the image and improve the scan quality. Most scanners come with a variety of approval options to check light sources and

3. Input index and parameter setting of scanner

1. Resolution

Resolution reflects the richness of detail in the image recorded by the scanner and can be divided into optical resolution (physical resolution) and interpolation resolution (maximum resolution). Optical resolution is the actual resolution of the scanner, which is the real resolution (vertical and horizontal values) obtained when the scanner hardware scans, and it is a key factor in determining the clarity of the scanned image. Interpolation resolution is the resolution enhanced by software operations to strengthen the complement, which does not add new information to the image, but is very useful for images with specific requirements or when scanning line drawings. In order to obtain the appropriate image quality, the scan resolution needs to match the number of lines added, for full-scale reproduction, the number of forged lines (lpi) is generally multiplied by a quality factor k(1.5 ~ 2.0) to determine the best scan resolution. Such as when the amount of money added to the network is 175lpi; If k=2, the scan resolution is 350dpi.

2. Bit depth

Description the color information sense of each pixel in the input image scanned is bit depth; Also known as sampling depth. It is generally 24 bits, that is, R, G and B each account for 8 bits, and each has 256 gray levels; It can indicate that 2(8+8+8)=16.78 million colors are true colors, and professional scanners should have a depth of at least 36 bits. While the current use of Photoshop can only process 24-bit images, images obtained with a scanner deeper than 24 bits need to be converted into 24-bit images before they can be processed in Photoshop.

3. Choose the right black and white field

The brightest point in the figure is the white field, which directly affects the hue level of the light tone and the middle tone, and the human eye is extremely sensitive to the change of the light tone, the setting of the highlight point will also affect the neutral gray balance of the color, when the white field is set too bright. Will cause the brightness part of the level lost; Set too dark, the overall level of the picture is dark. For a general picture, when the white field fixed point is neutral gray, the CMYK value of the white field can be 25, 0%, 0%, 0%. For the case where the white field is color biased; Must depend on the specific situation, through continuous accumulation of experience in order to improve the ability to judge.

The darkest point in the picture is the black field. The setting principle of black field is basically the same as that of white field. The difference is that the highlight point can be determined through the eye, and the black field of the image requires the operator to have a certain judgment. Some scanning software can automatically identify the black field, and some also provide certain tools (such as histogram adjustment) to determine the black field, the black field is too dark, will lead to the loss of the dark level, resulting in the "union" phenomenon. And if the black field is set too bright, it will cause the dark tone to be too bright. For most normal pictures, the K content of CMYK in the black field should not be less than 70%, and generally not more than 80%.