An Experimental Research to Compare Devices for Measuring Aluminum Lithographic Printing Plates

This research was experimental in nature and aimed to: (1) explore the feasibility of adopting a Micro Optical Image Capture System (MOICS) to measure halftone dots on offset metal printing plates, (2) investigate the differences in the measuring results of the three instruments: MOICS, Charge Coupled Device (CCD) Plate Dotmeter, and Conventional Reflection Densitometer, and (3) study the reliability and validity of MOICS when measuring metal plates. The three instruments were used to read conventional PS plates, photopolymer CTP plates, and thermal CTP plates. Forty plates were made resulting in a total of 120 plates. Plate dots at 10%, 25%, 50%, 75%, and 90% tone values were measured and their area readings were entered onto Minitab and SPSS statistical software packages for final analyses. The major findings of this study are: (1) The measuring results of MOICS on the metal printing plates were highly reliable and valid. (2) There existed significant differences between the measuring results of the three instruments at 10%, 25%, 50%, 75%, and 90% tints. (3) The measurements and calculations for the halftone dots on the plates of the self-established MOICS device involved in several steps and its process were relatively time-consuming. Further studies are recommended on how to integrate CCD Camera, digital video processing system, and image analysis and computation software application to build a compact and hand-held instrument.