Scanning will adjust the gray scale.
Resolution is the most important technical index of the scanner, which indicates the ability of the scanner to display image details, that is, it determines the fineness of the image recorded by the scanner, and the unit is PPI (pixels per inch). It is usually expressed by the number of pixels contained in the scanned image per inch. At present, the resolution of most scans is between 300-2400 PPI. The higher the PPI value, the higher the scan resolution and scanned image quality, but this is limited. When the resolution is greater than a certain value, it will only increase the image file, making it difficult to process, and will not significantly improve the image quality. For screen printing applications, scanning to 6000PPI is enough. There are generally two kinds of scan resolution: true resolution (also called optical resolution) and interpolation resolution. Optical resolution is the actual resolution of scanner, which determines the key performance index of image clarity and sharpness. Interpolation resolution is a numerical value to improve the resolution through software operation, that is, interpolation is used to fill the missing information around the sampling point, so it is also called software enhanced resolution. For example, the optical resolution of the scanner is 300PPI, and the image can be improved to 600PPI by software interpolation, and the details obtained by interpolation resolution are less. Although the interpolation resolution is not as good as the real resolution, it can greatly reduce the price of the scanner and is very useful for some specific tasks, such as scanning black and white images or enlarging manuscripts.
Grayscale represents the range of brightness levels of an image. The more levels, the wider the brightness range and the richer the layers of the scanner image. At present, the gray scale of most scanners is 256. Among the 256 gray levels, there are more gray levels than the naked eye can recognize.