Talk about the setting of scanner parameters

Since MICROTEK launched the world's first scanner in 1984, although it has only a history of more than ten years, the market and demand for scanners have shown a rapid growth. With the popularity of computers, scanners have become extremely popular as input devices for computers. With the increase of scanner manufacturers and the diversification of scanners, popular scanners are entering into millions of households and become a must. Indispensable computer input device.

No matter which type of scanner your manufacturer uses, you must first set the scan parameters before you scan the image, including the output image's control parameters and image enhancement tools. The following section mainly discusses the scanning resolution settings and some issues that should be noted when adjusting the gamma value.

Each scanning device has a resolution limit and produces the best image only when working within the limits. Ideally, scanning should be performed in a 1:1 ratio with an input resolution that is divisible by the scanner's optical resolution. For a 600ppi scanner, it should be 600ppi, 300ppi, 150ppi, 100ppi, 75ppi, and so on. If one of the other input resolutions is selected, the scanner must match and determine the average value when determining the color or grayscale value for a given pixel, which tends to reduce the tone integrity of the original image.

Scan resolution is divided into optical resolution and interpolation resolution. The optical resolution is the actual resolution of the scanner. It is the maximum amount of information the scanner's optical system can sample, and is the most critical factor in determining the clarity of the scan. Interpolation resolution refers to the amount of apparent information the scanner can capture with the help of a processor or software algorithm. When scanning, it is best not to scan with a resolution higher than the maximum optical resolution of the scanning device. When using interpolation resolution, the scanner uses hardware and software-based algorithms to add new data to the image. Although some algorithms are better, new details can never be obtained by interpolation, and since this method is The pixel values ​​are averaged, which actually deteriorates the sharpness and contrast of the image. But it is very useful for some images or scanning line drawings with specific requirements.

In practical work, the choice of scanning resolution can be determined according to the clearness of the image original and the use of the scanned document. For normal manuscripts, it is recommended to use a lower resolution when scanning because the resolution will affect the scanning speed and file size. When using true color or grayscale mode, use a low resolution of 100ppi-200ppi. The capabilities displayed by most printers and monitors have been exceeded. There is a geometric relationship between the scan resolution and the file length. For example, to scan a 3 inch by 3 inch photo using RGB, if the selected input resolution is 300PPi, the resulting image file is approximately 2 pixels long. .4MB, as in the following formula:

[3in.×3in.×(300ppi)]2×3÷1000=2.43MB

If you scan the image again and the scan resolution doubles to 600ppi, the file length will be 4 times as shown below:

[3in.×3in.×(600ppi)2×3÷1000=9.72MB

It can be seen that when the resolution is too high, the size of the file will increase geometrically, increasing the difficulty of the operation and occupying too much storage space. If the scanned image is only used as a screen display, under normal circumstances, set the resolution does not have to be greater than the screen resolution, only 72ppi, because the screen's highest resolution is only 72ppi.

In addition, in the scan settings, we can also adjust the Gamma option to adjust the color, initially try smaller changes, and see the effect. For example: scan night photos, if the photos are particularly dark (normally exposed photos), try increasing the gamma value (which can be increased to 1.6-1.9), which can increase the details of the shadow area, and will not affect The overall tone range of the image. If you scan bright photos such as snow photos, such as snow photos in bright sunlight, you can reduce the gamma (to 1.2-1.3), which can show the details of bright areas, and does not affect the overall tone of the image range.

The only way to achieve the best results is through constant practice. During scanning, when you preview the scan, the changes in these settings will be reflected in the preview window. You can change the settings in this way and you can check the results of the settings without actually scanning.