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Title: Optimization of grey reproduction in CMYK printing processes
Author: Beltrami, Alessandro
Tutor: Meler Corretjé, Lourdes
Others: Morán Moreno, Jose Antonio  
Keywords: printing
Issue Date: Jan-2022
Publisher: Universitat Oberta de Catalunya (UOC)
Abstract: Printing of grey shades is a challenge for almost all printing technologies: many factors need to be kept under control to allow a consistent reproduction of neutral greys, among them the correlation with human vision system. The scope of the project is to describe and to apply the state-of-the-art of the neutral grey balance and reproduction calibration in a generic 4-colours CMYK halftoned industrial printing process. A 3-steps calibration method is applied to be compatible with ISO 12647-2 standard and to achieve a neutral grey balance condition, inspired from G7tm method, focusing on the case when starting from an arbitrary characterization. The test was made using an HP Indigo industrial press on gloss coated paper, calibrated following FOGRA51 printing condition, and finetuned for grey balance reproduction using measurements from an automatic spectrophotometer. The Grey Index (GI) colorimetric formula was used to evaluate the result, supported by visual evaluation on a standard viewing condition. The results show improvement of GI from 2,82 of uncalibrated press to 1,16 using standard TVI calibration to 0,61 of the fine-tuned grey calibration, and the visual evaluation agrees with the results. This is a demonstration that the method works but more tests are needed to validate the process and correlation of the Grey Index formula with visual assessments in more printing technologies and paper substrate types.
Language: English
Appears in Collections:Bachelor thesis, research projects, etc.

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