How to check the scan quality of images teaches you 3 tips for checking scanned images
Today, color flatbed scanners are widely used in color desktop publishing In industries such as system and professional advertising design, household users have a strong demand for such products because of the improvement of living water products. Various facts have played a positive role in promoting color image processing, but how do we Can we get really high-quality scanned images? In the previous article, we have introduced to you that the factors that affect the quality of image scanning are caused by many aspects: resolution settings, color correction, image enhancement, file formats, file storage, and system resources are all involved. In fact, , even if all the above problems are solved, it does not necessarily mean that you can rest easy. To get a perfect scanned image, you also need to check the quality of the scanned image, and most users often This was inadvertently ignored.
To check the quality of scanned images, it is often necessary to start from the following aspects: image tone range, image color and image brightness.
Check image tonal range
For many novice users, checking image quality often means checking image tones, thinking that good color is equivalent to For good images, actually, this is only one aspect of the problem. To see whether an image is good or bad, the most critical factor is to check its tonal range, that is, the level of the image. The so-called level is the degree of change in the image from dark to bright. To check the level of an image, you need to use professional tools, such as some professional graphic image processing software Photoshop, ImagePais 2, the eyedropper tool in these software can check the level of the image, especially for the highlight area and shadow area.
If there are large areas of white and black with the same value in the highlight and dark areas, or if the value changes very little, it means that the image level is poor. Using the “Level function” in Photoshop, you can also check the quality of the image from the level distribution map. If a large number of dark pixels appear on the left, it indicates that the entire image is dark; if a large number of bright pixels appear on the right, it indicates that The whole image is bright; an image with good scanning quality has clear layers and a very uniform color gradation distribution. In addition, the “Histogram function” in Photoshop can also help the user to check the condition of the scanned image to see if the continuous layers transition smoothly from light to dark, or if there is a band gap, if there is an obvious band gap, the user The selected scanner density value is low and should be adjusted accordingly.
Check the image color
When the image has enough gradation, you should check the color balance of the image, that is, whether the image has a color cast. The easiest way to check color balance is to check for neutral grays. Gray balance is the gradation process from the smallest black (0%) to the largest white (100%) in the image, and is one of the important parameters for converting from RGB to CMYK. Theoretically speaking, mixing equal amounts of C, M, and Y inks will produce neutral gray, but in fact, due to the difference in ink quality, there will be more or less deviations in a certain proportion. to achieve neutral gray. The user can determine the correct CMYK value from the Printing Inks Setup function in Photoshop.
The easiest way to check the image color is to open the Info panel in Photoshop, move the cursor to the brightest highlights and darkest shadows of the image, pay attention to the data displayed on the Info panel, if the highlights The RGB values read between 250 and 5 in the low-key area and the low-key area indicate that the tonal range of the scanned image has sufficient detail and the image quality is very good.
In addition, you should also check the image’s impression color to see if the colors of the sky, grass, and flowers are harmonious and unified, but this requires human judgment and lacks scientificity. Because the judgment of color is a complex visual and psychological process, each person has different aesthetic viewpoints and personalities, and has a special preference for certain colors, so this method can only be used as a reference method for color inspection.
Check the brightness of the image
It is also important to check the brightness of the image, by comparing it with the original to see if the scanned image is too dark or too bright, too dark or Too bright will not get the ideal image. Brightening an image that is too dark, adjusting the gamma value is certainly an easy way, but doing so can make the scanned image lose its information. In fact, the easiest way to check the brightness of an image is to compare it to the original and try reading the color values on the scanned image in CYMK mode to see if it is close to the original.
In fact, the scanning process is never easy, but there are too many variables involved in getting a high-quality scanned image. Based on the experience of using the scanner for many years, I think that if you want to get a perfect scanned image, the quality control of the scanned image is very important, and doing the above points carefully is undoubtedly an important factor for obtaining a perfect output.
