Method to adjust the print quality of print images in an electrophoretic digital printer

A method to adjust print quality of print images in an electrophoretic digital printer with at least one print group, comprising the steps of:

• generating with the print group with an electrophotographic station of the print group charge images of the print images;
• with a developer station, developing the charge images into toner images using liquid developer having carrier fluid and toner;
• transfer-printing the toner images onto a recording medium in a transfer station;
• with said print group generating on the recording medium a first control marking with elements of the first control marking being aligned transverse to a printing direction;
• measuring a shape of the elements of the first control marking to generate a first measurement signal;
• also with said print group generating on the recording medium in addition to the first control marking a second control marking with elements of the second control marking being aligned in the printing direction;
• measuring a shape of the elements of the second control marking to generate a second measurement signal;
• calculating a ratio of the first and second measurement signals of the first and second control markings, and comparing said ratio with an additional nominal value;
• and
• given a difference between the ratio and the additional nominal value, generating an adjustment signal via which an amount of the carrier fluid in the liquid developer is varied so that the ratio approaches the additional nominal value.