Controlling flexographic printing system pressure using optical measurement

A method of controlling an ink transfer pressure between cylinders in a flexographic printing system, the method comprising:

• providing a flexographic printing plate on a printing cylinder, the flexographic printing plate including:
• an image region including a plurality of raised printing elements arranged to print an image pattern having printed image features corresponding to the raised printing elements, wherein the printed image features have a smallest lateral dimension that is less than 25 microns;
• and
• one or more pressure characterization regions outside the image region, each pressure characterization region including a plurality of raised printing elements arranged to print a pressure characterization pattern having printed characterization features corresponding to the raised printing elements;
• transferring ink from an anilox cylinder to the flexographic printing plate on the printing cylinder, wherein the anilox cylinder and the printing cylinder contact each other with a first transfer pressure;
• advancing a recording medium through a nip between the printing cylinder and an impression cylinder such that ink is transferred from the flexographic printing plate to the recording medium to print the image pattern and the pressure characterization patterns, wherein the printing cylinder and the impression cylinder contact each other with a second transfer pressure;
• measuring an optical property of at least one printed pressure characterization pattern;
• and
• adjusting one or both of the first and second transfer pressures responsive to the measured optical property of the at least one printed pressure characterization pattern.