Tips for improving scan quality

To scan high-quality images, we must master certain scanning techniques. I hope that the following can give you some help.

1, determine the appropriate scanning method

Scanners allow you to scan images, text, photos, etc. Different scan objects have different scan methods. Open the driver interface of the scanner, we found that the program provides three scanning options, including "black and white" method for black and white characters of the original or OCR recognition; "grayscale" applies to both graphic and text mixed graphics and text For example, scanning this type takes into account both text and pictures with multiple gray levels; “photos” are suitable for scanning color photos, which require multiple levels of sampling of red, green and blue channels and storage. Before scanning, we must first select an appropriate scanning method based on the object being scanned, in order to obtain a higher scanning effect.

2, optimize the scanner resolution

The higher the scanning resolution, the clearer the image is, but considering that if the resolution of the output device is exceeded, then a clear image cannot be printed out. It merely occupies the disk space and has no practical value. Therefore, it is necessary to select the proper scanning resolution. You can scale down large images after scanning. For example, we scan a 4 x 4 inch image at 600 dpi, and reduce it to 2 x 2 inches in the build program. Its resolution is 1200 dpi.

3, set the size of the file

Regardless of whether the object being scanned is text, images, or photos, the images output by the scanner are all images. The size of the image directly relates to the size of the file. Therefore, we should set the size of the file when scanning. Usually, the scanner can automatically calculate the file size when previewing the original manuscript, but knowing the file size calculation method will help you to make proper choices when managing the scanned file and determining the scanning resolution. The calculation formula of the binary image file is: horizontal size × vertical size × [2 (scan resolution)/8]. The color image file calculation formula is: horizontal size × vertical size × [2 (scan resolution) / 3].

4, set the scanning parameters

When the scanner pre-scans the image, it scans according to the system's default scan parameter value. The effect may be different for different scan objects and different scan modes. Therefore, in order to obtain higher image scanning quality, we can manually adjust the parameters, such as when the brightness of the grayscale and color images is too bright or too dark, you can drag the slider on the brightness slider. Change the brightness. If the brightness is too high, the image will look white; if the brightness is too low, it will be too dark. You should make the brightness of the image moderate when you drag the brightness slider. The same for other parameters, we can follow the same adjustment method to make local modifications until your visual effects are satisfied. In short, a good scanned image should try its best to eliminate the need for more adjustments by the image processing software to satisfy the printout and the closest to the print quality.

5, store the curve and load the scanning software

Sometimes, in order to get the best color and scan contrast, we first do low-resolution scanning, open it in Photoshop, and use Photoshop's curve function to make color and contrast improvements. The curve is stored and loaded back into the scanning software and your scanner will now use this color correction curve to create a better high resolution file. If you scan several images with a similar color gamut range, you can use the same curve, and you can also store the curves often and load them back as needed.

6, according to the desired effect to place a good scan

In the actual use of images, we sometimes hope to obtain images with a tilt effect. Many of our designers often input images to a computer through a scanner, and then use professional image software to rotate them so that the image can be reached. Rotation effects, as everyone knows, this process is a waste of time, according to the size of the rotation angle, the quality of the image will decline. If we know in advance how the image will be placed on the page, then using the protractor and the bottom edge of the original to place the original on the roller and platform at a precise angle will yield the highest quality image without having to rotate it in the image processing software. .

7. Find the best scanning area on the glass plate

In order to obtain the best image scanning quality, we can find the best scanning area of ​​the scanner, and then place the object to be scanned here to obtain the best and most fidelity image effect. The specific steps are as follows: First, set all the scanner's controls to automatic or default, select all areas, and then scan a blank, white or opaque block sample at low resolution; then use professional image processing software. In Photoshop, open the sample and use the software's averaging command (Equalize menu item) to process the sample draft. After processing, we can see where there are cracks, stripes, and black spots on the scanner. We can print this file and cut out the best area (that is, the most stable area) to help us place the image.

8, use transparent film accessories for the best scanning effect

Many flatbed scanners are equipped with a transparent piece fitting on top of the scanning bed. To obtain the best scanning of a transparency or slide, remove the picture from the shelf and slide mount and install it on a glass scan bed with the reverse side down (usually the matte side). Cut out the mask with black paper and cover the entire scan bed except where the manuscript is set. This will reduce glare and excessive exposure during scanning. Similarly, when scanning a 3D object, cover the scanner lid with an object whose color contrasts strongly with the object you are scanning. This will help you to select it more easily with Photoshop's ColorRange tool.

9. Maximize the gamut of scanned images

To take full advantage of the 30- or 36-bit scanner to increase the color range, use scanner software (such as Agfa's FotoTune) or other company's software to adjust the color as much as possible. Because Photoshop software is limited to 24-bit images, our images may be inserted with the widest color gamut.

10, use network technology to scan prints

When scanning prints, nets appear on successive adjustments of the image. If your scanner does not have a net-going feature, try to find the smallest resolution possible. Frequently, the same or twice the resolution of a printed cable may work. Once you get a fairly good scan, using Photoshop is a Gaussian Blur filter (with a setting of less than 1 pixel) to soften the net slightly until it is not visible. Then apply the Unsharp Mask to sharpen the image back. You can also improve the scan by slightly rotating the image, because the continuous adjustment of the screen angle is changed. Rotate the black and white image 45 degrees exactly. For CMYK images you will need experimentation.

11, scanning real objects to use CCD scanner

Currently there are four types of photosensitive devices used in scanners on the market: photomultipliers, silicon oxides, and semiconductor isolated scanners (CCDs), and contact sensitive devices (CIS or LIDE).

CCD is now the mainstream, the principle is simply: thousands of to tens of thousands of phototransistors are integrated on a silicon single crystal. These phototransistors are divided into three columns, which are covered with red, green and blue color filters respectively. Color scan.

Contact light-sensitive device (CIS), which uses a photosensitive material is generally used to manufacture cadmium sulfide photo-resistor, the production cost should be much lower than the CCD (the same accuracy of the CIS scanner is always better than the CCD scanner on the market This is why this is a lot cheaper.) Scanning distances are short, scans are low in definition, and sometimes even in nominal values. Temperature changes tend to affect scan accuracy. These are the fatal problems of such scanners.

The CCD scanner uses an optical lens to image the CCD surface, so it has a fairly long depth of field, and it gives a clear scan of the spine and even the real thing. Due to the design of the CIS optical path, the depth of field of its imaging is very shallow, that is, the clear range that can be satisfied in the height direction of the scanner is very small, and the actual depth of field is only -0.3 to +0.3 mm. This requires that your document must be tightly affixed to the glass during the image scanning process, otherwise a slight unevenness will cause the image of this part to be blurred. The depth of field of the CCD (±3mm) is at least ten times that of the CIS (±0.3mm), which means that the CCD scanner scans the 3D object within a certain range very clearly and vividly; the CIS scanner scans slightly uneven In the case of objects, the output images often appear blurred and defocused.

In general, most of drum and hand-held scanners use CIS technology, while flat-panel scanners mostly use CCD technology.

Reprinted from: Hunan Computer Network