Test method for scanner color reproduction capability

Most scanners have been calibrated at the factory, but due to differences in manufacturing conditions, changes in the color temperature of the light source, newness, etc. will affect the scanner's pointer. When purchasing flatbed scanners, manufacturers typically provide a standard transmissive or reflective original that includes a neutral grey scale and partial color patches. After the normal scanning of the standard manuscript, observe the image of a line in photoshop6.0 (observe the white line or the black line is particularly obvious) rgb three-channel pixels coincide, in order to check the scanning accuracy (observe should be selected at high magnification ). The rgb channels do not correspond to pixels. On the one hand, the sharpness of the scanned image will be affected, and on the other hand, the effect of color reproduction will be affected during copying.

Neutral ash scales were used to examine the ability of the flatbed scanners to restore neutral gray color and to express changes in the density level of the ladder. The correct restoration of the neutral gray color by the scanner is the premise and basis for identifying colors and restoring colors. Scanning color deviation is caused by the difference in the color performance of the scanning components and the standard components during the scanning process. Even though the scanner has been calibrated before shipment, some color casts are inevitable in use. In the actual process, the display screen is often corrected so that it can correctly display the color, and then correct the scanning color cast.

At present, prepress production centers use medium and high document scanners. Most of the software can customize the output profile. For example, the rgb output characteristics culture can be defined in Heidelberg scanning software newcolor. Just set the output profile in the scanning software to be the same as the "rgb setting" in photoshop, so that the image display in photoshop is nearly the same as the screen display in newcolor. Scanner profiles are not supported for scanners with lower file sizes, and photoshop functionality can be used.

When correcting scanning color cast, put the scanned neutral gray ladder into photoshop6.0 image processing software, use the information palette to display the rgb values ​​of the steps in the image, call curves curve to adjust rgb three channels Until each step cmyk display value in the image reaches the required value of neutral gray, at the same time, the visual neutral gray scale can be visually observed on the display screen. The curve at this time is the color curve after the scanner corrects the color cast. When the image is scanned, the color after the scan should be properly compensated according to the curve. The curve can be saved for recall. By scanning with the color patches in the standard document, the scanner can determine the reproduction characteristics of each color. The visual contrast between the original color patch and the scanned image can qualitatively recognize which colors the scanner reproduces better, and which colors are worse, so that in the future, in the scanned image, the color of poor reproducibility is corrected by the image processing software. In addition, the scanner should be calibrated regularly.