Abstract: Image quality assessment test charts and objective image quality measurement systems may be used to evaluate the printer sub-system health before artifacts become objectionable to human observers. Diagnostic images may be printed to allow measurement of a number of system performance attributes, such as: density, banding, streak, granularity, mottle, color, gloss, gloss uniformity, edge gradient, raggedness, sharpness, background, registration, line width, and satellite measurements. By comparing these measurements to historical values or ideal values of the same measurements, preventive maintenance suggestions may be generated to avoid both unnecessary maintenance and objectionable print quality.

Abstract: Controlling the charge on toner in a development station of an electrographic reproduction apparatus, wherein data relative to latent image charge carrying member voltage and image density control patches are sensed and development potential to achieve an aim density is calculated therefrom. A delta from an optimum development potential range is calculated, and in response to the determined delta, an amount of liquid charge control agent, from a supply of suitable liquid charge control agent, necessary to be added to the developer material in the development station to bring the toner to substantially a charge level that will enable a desired optimum developer potential is calculated. The calculated amount of liquid charge control agent is then injected directly into the development station.