A method of generating a diagnostic plot for a printing system includes printing a first half of a diagnostic pattern representative of a first state of the printing system, and printing a second half of the diagnostic pattern representative of a second state of the printing system. Variation of the diagnostic pattern from an adjacent diagnostic pattern indicates the printing system is out of specification.

A printing apparatus includes a printing section, an imaging section, a color measurement section, and a discharge amount upper limit determining section. The imaging section is configured to capture an image of a test medium on which a test pattern has been printed. The color measurement section is configured to execute color measurement on the test medium. The discharge amount upper limit determining section is configured to determine an upper limit of an amount of ink to be discharged based on at least one of a color saturation suppression upper limit calculated based on color measurement information of the test medium obtained by the color measurement section and at least one of an overflowing suppression upper limit, a bleeding suppression upper limit, and an aggregation suppression upper limit calculated based on imaging information of the test medium obtained by the imaging section.

A method of generating a diagnostic plot for a printing system includes printing a first half of a diagnostic pattern representative of a first state of the printing system, and printing a second half of the diagnostic pattern representative of a second state of the printing system. Variation of the diagnostic pattern from an adjacent diagnostic pattern indicates the printing system is out of specification.

The invention is focusing on an inkjet printer as well as on a method for operating an inkjet printer, in which for at least one color at least two inks of the of the same color, but of varying color intensity are used, namely one ink of a lighter color intensity J.sub.h and an ink of a darker color intensity J.sub.d, where preferably to following applies: J.sub.d=2.sup.x*J.sub.h, with x for example being 2, 3 or 4. Then 2.sup.x is in these case 2.sup.2=4, or 2.sup.3=8, or 2.sup.4=16; whereat several ink drops are printed on one pixel on top of one another in quick succession, namely 0 . . . (2.sup.x1) ink drops so that with the darker ink 2.sup.x brightness levels can be accomplished, and with the lighter ink likewise 2.sup.x brightness levels, what from altogether 2.sup.x*2.sup.x=2.sup.2x different brightness levels are resulting; and where the individual drops unite together during their flight or do not come loose from each other, resulting in only one single color drop per pixel on the printing substrate.

A method performs forming a test pattern on a medium, the test pattern including a plurality of patches having different ejection amounts per unit area, determining an ejection amount minimum value that is a minimum value of the allowable range and an ejection amount maximum value that is a maximum value of the allowable range based on an ejection amount reference value that is a reference of an allowable range of the upper limit value of the ejection amount, determining a provisional ejection amount upper limit value that is a provisional value of the upper limit value based on a reading result of at least a part of the plurality of patches, and the upper limit value is determined so as to be based on the ejection amount minimum value, the ejection amount maximum value, and the provisional ejection amount upper limit value.

Printing with a single colorant a security feature imperceptible to the naked eye. For a digital security image having a first region formed by a first pattern of binary pixels and a second region formed by a different second pattern of binary pixels, the first and second patterns are printed with the single colorant. A darker one of the first and second printed patterns is determined. The security image is printed with the single colorant, the region corresponding to the darker printed pattern printed at a reduced gray level such that the printed first and second regions appear substantially indistinguishable to the naked eye.