| 摘要 |
On a lithographic plate for printing, there is provided an identification mark which indicates for which color the lithographic plate is and in which printing press the lithographic plate is to be used. The identification mark of the lithographic plate is simultaneously recorded when image area rates of the lithographic plate are measured. When the measured lithographic plate is mounted in the printing press, the data of image area rates which have already been measured and recorded are read utilizing the result of reading the identification mark. The data are transmitted to the printing press and used for control of the ink supply amount of the printing press. In order to carry the lithographic plate keeping a flat state, there is provided a difference between air pressure acted upon one surface and another surface of the lithographic plate. A locating apparatus is also used so that the lithographic plate is set at a correct measuring position in order to measure image rates of the lithographic plate. An image rate can be thereby correctly measured for each portion of the lithographic plate.
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