Discussion on the quality of scanned images

The scanner can be used to scan colorful and colorful images and texts. Its applications range from family to professional printing.

With the popularization and development of computers, color printing systems have mushroomed and have been widely used in various fields such as advertising, light printing, newspapers, publishing, and even households. As an advanced computer's image input device - flatbed scanner, it has reached a level of purity and love. Nowadays, digital imaging devices such as scanners have become one of the indispensable external devices for computers. In the application of image systems, more than 70% of input images are input using flat panel scanners. In the increasingly widespread use of flatbed scanners, how to identify the quality of the scanned image is very important.

In order to judge the quality of scanned images correctly, first, check your originals and you must use a good quality original for scanning. Because the scanned image is always better than the quality of the original (in the case of a basic preset scan). Therefore, if your original is of poor quality, use the many functions provided by the Scan Wizard software to correct the original image.

Second, you must correct your system based on information provided by vendors (such as monitors and printers). If you use a CMS (Color Management System), make sure that it is under the correct correction conditions, or at least you should follow The instructions for correcting the display in the Adobe Photoshop user manual are used to correctly display the scanned image because a good display and full color display card are necessary for checking the quality of the scanned image.

First, check the tone range

Check the highlights and shadows to see if there are enough fine levels. If not, the highlights and shadows will appear as white or black with the same value, or the value will change very little. Using Photoshop's "Level" or "Histogram" can help you check the condition of the scanned image, and also check whether the continuous level changes smoothly from bright to dark or shows a band gap if there is a clear band. Gap, your scanner density range is low.

Second, check the color

Check if the color of the scanned image is balanced, or check the image for color cast. The easiest way to check the color balance is to check the neutral gray and see if there is a color cast, or check the color of the impression (such as the color of the fruit, sky, grass and flowers) to see if any of the colors are unnatural; check the saturation of the scanned image The degree is good enough, compared with the original is too dark or too bright. We can use image processing software to correct color balance and saturation.

Third, check the clarity

If the scanned image has an unclear focal length, the scanner may have a problem. It may be that the vibration during the scan is too great, and perhaps the registration is too bad. Images scanned by a good scanner should have sufficient sharpness to get good detail (at least in the midtone part). However, the CCD scanner still does not reach the definition of the drum scanner compared to the drum scanner because there is a virtual light mask function (completed by hardware) in the drum scanner, and in the CCD scanner, There is no such hardware to perform the dummy mask function.

Fourth, check the brightness

By comparing with the original, whether the scanned image is too dark or too bright, too dark or too bright is not a good scanned image. Adjusting the gamma value brightens the dark image, but it causes the scanned image to lose information. Therefore, a good scanned image should have the correct light meal, and the user does not have to make too many adjustments. In fact, to tell whether a scanned image is good or bad is not a sham and simple work, because it requires the user to understand the basics of color and scanner. However, in some cases, good and bad, the user is still very easy to judge, the easiest way is to compare the scanned image with your scanned manuscript, but this is also controversial because of your display status and ambient brightness Conditions may lead you to make wrong judgments. Therefore, try to read the color value on the scanned image to see if it is close to the color value of the original, and it is best to perform it in the CMYK mode.

It should be emphasized here that most of the current platform CCD scanners use the RGB mode to scan. If a good RGB image is converted to a poor CMYK image, it is not the cause of the scan, but due to the poor conversion. This is an industry issue that needs further discussion. In short, the quality of the scanned image directly affects the output quality, and the image quality is related to the optical resolution of the scanner. Therefore, a scanner with a higher optical resolution must be selected so that the scanning can achieve clear gradation, vivid colors, and vivid vividness. Satisfactory image effect