Correct choice of color mode for scanned images

When scanning a color image with a scanner, three color modes are encountered: RGB, CMYK, and Lab, which are suitable for different occasions, respectively.

RGB color mode and application

The RGB color mode is the most common color mode. Basically all scanners have this color mode. When the scanner scans, the light emitted from the scanner light source is converted into R, G, and B electronic signals through various optical devices and A/D converters, so the quality of these RGB color information is mainly determined by the scanner. The hardware system decides that it has little to do with its software system. We must fully take this into consideration before selecting the color mode before scanning a color image.

Since the scanning software of the middle and low-end scanners does not have color correction data settings suitable for different printing conditions (paper, ink, etc.), the RGB color mode is mainly applied to middle and low-end scanners, and after the end of the scanning, image processing software (such as Photoshop) is used. ) Make appropriate color mode conversions and adjustments.

CMYK color mode and applicable occasions

CMYK color mode is another common color mode for color image scanning. Most scanners have this color mode. However, because the CMYK color information obtained in this color mode is converted from the RGB color information obtained by the scanner hardware, the quality is determined by the following factors: First, the hardware level of the scanner; Is the number of color correction data in the scanning software; Third, the operator's experience. Under different printing conditions (equipment, paper, ink, etc.), before scanning, the scanning parameters must be adjusted accordingly, such as the type of paper ink, the maximum amount of ink, the dot gain value, and the gray balance curve. The setting, the accuracy of these data directly affects the quality of CMYK color information. Since the setting of these data requires the operator to look at the manuscript according to his/her own intuition, the operator will be different and the set data will be different, resulting in a different color reproduction. Therefore, it is necessary to faithfully reproduce the manuscript or obtain a customer satisfaction. The quality of the required separations and the experience of outstanding operators are the key. In most new types of scanners, the manufacturer's established color correction settings have been stored in the form of documents, and users can even generate color correction files based on their actual conditions. Since a color correction file suitable for the original document and the printing conditions is added, even an operator who has no scanning experience can easily input data and obtain a high-quality scanned image.

Due to the low hardware level of the middle- and low-end scanners and the less color correction data, sufficient data cannot be provided when the RGB color information is converted to CMYK color information, and the quality of the CMYK color information is poor. Therefore, the middle- and low-end scanners are not suitable for CMYK. Color mode scans color pictures.

Lab Color Mode and Application

Lab color mode is a color mode unique to high-end scanners. It has a series of advantages that are different from the RGB color mode and the CMYK color mode. For example, Lab has the widest color space. It contains RGB color space and CMYK color space. Therefore, the Lab color information obtained by the scanner is converted to other colors. In the information, color deviation will not be caused because of insufficient information; Lab color information is also converted from the RGB color information obtained by the scanner hardware, but it will automatically make up for the color filter and the optical device during the conversion process. Insufficient; Lab color information is independent of the specific equipment, does not contain the personalized information of the specific equipment, which is especially important for guaranteeing off-site scanning production, and the consistency of scanned image quality between scanners of different grades and brands.

The Lab color mode is suitable for various occasions where the RGB color mode is applicable. It is also applicable to the case where a picture scanning production is completed by a plurality of companies and the case where an image of the same layout needs different scanners to be scanned.


Volkswagen Daily Printing Company Qi Zhen Source: Digital Printing