Precautions when scanning different original types

The quality of the image scanning determines the final quality of the image. How to obtain the best quality image is a long-term common topic for the industry. The quality of the scan has a great deal to do with the scanner, scanning software, and the actual experience of the operator. Control quality is nothing more than manuscripts, scanning equipment, scanning parameter settings and scanning techniques. In the following, I will discuss some aspects of the scanning quality in connection with work practices.

First, the original type and original analysis

The faithful reproduction of manuscripts is the eternal pursuit of the industry. Therefore, manuscripts are the prerequisite and basis for ensuring the quality of color reproduction.

1. Color copying of originals

1 high definition. It is the basis for realizing the price, color, texture, three-dimensionality, perspective, etc. of recorded scenery; 2 Density contrast. The density contrast of the original must be normal. It is generally required that the manuscript contrast be between 1.8 and 4.0. The manuscripts of such manuscripts are rich in tone, midtones, and shadow tone, and the coordination levels are normally distributed. The color saturation is good, and the texture is vivid (if there is a rich dark tone level; there are few levels in the fill level, you must open the dark tone level during the scan, the pressure level midtone level); 3 color saturation. The original is checked under the standard light source (50O0K). The color saturation is the true response to the wave picture object. Only the original with large color saturation can be a manuscript with normal color tone; 4 image particles. The granularity of the original affects the color, level, and texture. Fine-grained originals are conducive to the reproduction of levels and tones (especially bright textures) and true representation of colors.

2. The manuscript is usually divided into three types: transmissive manuscripts, reflection manuscripts and quadratic manuscripts

The second manuscript: that is, scouring goods; the density range is small, the level is not abundant, generally only the original large scan, not suitable for amplification. Usually the quality of a good secondary manuscript has a density range of only about 0 to 1.6. Far less than the scanner's density recognition capability, scanning this type of document can only be done with a normal flatbed scanner. Secondary manuscripts often have problems with color shifts and require proper color correction during scanning. It needs to be reminded that the scanning of the original manuscript must be done to the network processing.

Reflection draft: 1 photo. The range of high-quality photos has a density range of only O to 2.2, which basically meets the pre-press processing requirements and print suitability; it is the most common manuscript in our daily work. 2 physical.

Transmittal: 1 negative film. Normally, the negative film is not scanned directly. It is best to rinse the negative film into a photo and scan again. This is because, first, the negative film has no effect. It is not easy to restore the color; second, the film base of the negative film has a colored film, which can cause the negative film to have no white field and it is difficult to calibrate. 2 positive films (slides). It is a negative film, such as 135 slides. Its film base is not as good as the reversal film, the density range is small (0 to 2.8), and the particles are rough, and the scanned image is also relatively dirty. Its magnification can only be controlled at 4 to 7 times, and then it is larger. It will be distorted. 3The reversal film, also known as the film, is different from the negative film and the positive film in terms of the film material and the process used. The quality is the best among the original documents. The stability range is between 0 and 3.8. It can be enlarged when scanned. Several times is the best manuscript.

3. Analyze the original

The operator should have a certain amount of experience and manuscript analysis capabilities, according to the actual situation of the original; set the scanning parameters to obtain the best scanning quality. In actual operation, special attention should be paid to avoid automatic tuning of any parameters. To make the picture even, even not meet the printing requirements. For color cast pictures. If there is a rich experience in color correction, it is better to calibrate the channels when scanning, and it is better to perform the correction in PhotoShop after scanning.

Second, scanning preparation

To get the ideal threshold scan image, do a little preparatory work and test in advance; it will not only save a lot of time, but also effectively improve the scan quality.

1. Warm up. The scanner requires a few minutes of warm-up. The scanner should be turned on 30 minutes before the start of the scan.

2. Scanners are regularly cleaned and maintained. Scanners should be regularly cleaned and maintained in accordance with the requirements of the scanner instructions. When the scanner is not in use, apply a dust cap and do not allow the scanner to drench the water.

3. Clean the handles before scanning to avoid contamination of the scanned image by fingerprints. Do not use your mouth to blow dirt and dust on the scanning platform glass.

4. Clean the surface of the object or image used for scanning. It can be blown with a balloon, and the surface can be cleaned with water depending on the object being scanned, but damage to the object should be avoided, especially care should be taken not to leave scratches on the surface of the photo and film. Care should be taken when cleaning some of the original artwork.

5. Make the original flat. If you use software to repair the traces of the original curl. It will reduce the clarity and quality of the image. Although there are many functions in Photoshop (such as blurring and sharpening) to process the image, this is not the best way to solve the defects in the scanned image.

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

Stepper motor. Running the school uniforms option once a day will keep the scanner's force working state stable.

Third, the scanner's input indicators and parameter settings

The difference in the quality of the scanned image largely depends on the input indicators (such as bit depth, resolution, etc.) of the different scanners and the setting of each input indicator. Practice has proved that only for the different types of originals, the correct setting of the scanner's scanning parameters, can get the best image color, level and clarity, to ensure high-quality color reproduction.

1. Resolution

The resolution reflects the richness of the details recorded by the scanner and can be divided into optical resolution (physical resolution) and interpolation resolution (maximum resolution). The optical resolution is the actual resolution of the scanner. It is the true resolution (vertical and horizontal values) obtained when the scanner hardware scans. It is a key factor in determining the clarity of the scanned image. Interpolation resolution is a resolution that is enhanced by software operations to enhance the complement. It does not add new information to the image, but it is useful for images that have specific requirements or scan line drawings. In order to obtain proper image quality, the scanning resolution must be matched with the number of screen lines. For the original size copying, it is usually determined by multiplying the number of lines (lpi) by the number of lines (lpi) by a mass coefficient k (1.5 to 2.0). Scan resolution. For example, when the amount of money added to the network is 175 lpi; when k=2, the scanning resolution is 350 dpi.

2. Bit depth

Describes the bit depth of each color pixel information in the scanned input image; it is also referred to as the sampling depth. It is generally 24 bits, that is, R, G, and B each occupy 8 bits, each with 256 gray scales; it can represent 2(8+8+8)=1678 million colors as true color, and the professional scanner should at least There are 36 depths. At present, the use of cultivable Photoshop can only deal with 24-bit images. The images obtained with a scanner with a bit depth of more than 24 bits need to be converted into 24-bit images in order to be processed in Photoshop.

3. Choose the right black and white field

The brightest point in the picture is the white field. The white field directly affects the tone levels of the bright tone and the middle tone. The human eye is extremely sensitive to the changes of the bright tone. The setting of the high light point will also affect the neutral gray balance of the color. When the white field is too bright. It will cause some levels of highlights to be lost; it will be too dark and the overall level of the picture will be dark. For a general picture, when the white field is set to neutral gray, the CMYK value of the white field may be 25, 0%, 0%, 0%. For the white field is a color cast; must be determined by the specific circumstances, through the accumulation of continuous experience can improve the ability to judge.

The darkest point in the picture is the black field. The setting principle of the black field is basically the same as that of the white field. The difference is that the highlight point can be determined through the eyes, and the black field of the image requires the operator to have a certain degree of judgment. Some scanning software can automatically identify the black field, and some also provide certain tools (such as the adjustment of the histogram) to determine the black field, and the black field is too dark, which will result in the loss of dark tone levels and cause the phenomenon of “merging”. . The black court is too bright, it will cause the dark tone too bright. For large, mostly normal images, the K content of CMYK in the black field must not be less than 70%, and generally not higher than 80%.

In general, during the scanning, the difference between the ink field and the dark tone level, the white field and the bright tone level is compared, and the scanning effect is judged by the numerical comparison indicated by the “probe”. Do not trust the color effect of the screen display.