This research in regards to paper topography and roughness and their influence on print quality is a continuation of the research presented at the 2010 conference in San Diego. For that research comparisons were made in regards to the print quality between offset and digitally (toner-based) printed products. The comparison was made between coated and uncoated stocks. This research expanded the comparison to the stocks with matte surface finishing. It was found that there was a direct correlation between the topography of the tested papers and the resulting circularity of the printed dots for offset printed products. For digitally printed products the roughness value of the tested papers correlated better with the resulting dot circularity. The evaluation of the printed samples took place with the use of high-end precision flatbed scanner and computer based image analysis software called Verity IA.
During the previous project open-source software called ImageJ was also tested for the evaluation of the tested papers. The functionality of the open source software can be extended through plug-ins. An initial correlation between the roughness values of both software solutions was found, but further analysis is required, since some of the tested papers did not give consistent results with both applications. It will also be tested how other plug-ins can be used for obtaining better results and also give the open source software, to a degree, similar functionality like the commercially available software. The scope of the previous research paper will be extended to include additional coated and uncoated papers that will be tested on an offset and a digital printing press.
Toners used in digital print technologies are more opaque then lithographic inks, which are mostly transparent. This poses a unique challenge for the image based analysis software, since the software was initially developed for the evaluation of offset printed products. Optical print density will be evaluated for offset and digitally printed test forms and the results will be compared conventionally obtained print density values through the use of a densitometer. It will also be tested if both software solutions can be used to determine the printed density through image analysis.
The circularity plug-ins for ImageJ gave very similar results for all the tested papers, independent of the amount of printed dots included in the sample area and any image enhancement that has been done prior to the analysis.
A 3D-plugin for ImageJ created a 3D-map of the tested papers, which in turn illustrated nicely the obtained topography and roughness evaluations done through the Verity IA software.
Our conclusion is, that the Verity IA software is more versatile and fine-tuned than the ImageJ software, which has been enhanced in its functionality through plug-ins for this study and can be considered an additional tool to the commercially available software solution.
The correlation in regards to the roughness evaluation of a tested paper still exists between both software solutions.