Application of Digital Imaging to Measure Print Quality

Abstract

The printing industry has placed a major thrust to understand and manipulate print quality. One of the important aspects of poor print quality in high speed printing is color density variation in solid areas, known as mottle. We describe applications of digital imaging for reproducible, objective measurement of mottle. We quantify the variations in print density using a digital image analysis system, which includes a Flatbed scanner, a Macintosh Power PC, and the NIH image program. Print mottle was correlated to the local standard deviation of the lightness values divided by the local mean of the lightness values.One of the major difficulties in communicating the results of mottle measurement is that different detectors interpret color differently and light sources on the scanners vary, thus affecting the color consistency between scanners. Employing a Color Management system to the measuring technique allows the measurements of the digitized images to have universal values. Calibration of scanners allows different locations using different scanners at different times to obtain and compare mottle values using the same relative scale.A number of field examples will be presented to describe the evolution and application of the technique.