Method for calibrating a color marking engine for halftone operation

An apparatus for calibrating the half-tone operation of a color marking engine for creating images formed in bi-level or quad-level dot density formats, comprising:

• at least one color marking engine operable for creating half-tone images formed in bi-level or quad-level dot density formats;
• a test pattern for running on each color marking engine to provide an output image of a plurality of gray patches formed of first, second and third color toners associated with said color marking engine wherein said gray patches include first, second and third sets of patches reproduced respectively at dot density levels of 25%, 50% and 75% of a maximum density and wherein relative color toner levels in said gray patches within each said first, second and third sets of patches vary a predetermined increment in value above or below said toner levels in a median valued gray patch;
• an output of each selected color marking engine, which is operable to provide said output image whereby said output image may be visually selected for having a minimum of color shift associated therewith in accordance with predetermined visual criteria;
• and
• a memory for storing a correction factor, determined for each color and defined at a maximum dot density thereof, said correction factor corresponding to an offset value from said maximum dot density for output images created at said bi-level and quad-level formats.