Image-based closed-loop color control systems offer unique advantages over color bar-based systems. With those advantages come several new challenges for both the printer and the color control system designer.
Calculation of the target image is impacted by all parts of a printer's workflow. Each step must be carefully analyzed, and any modifications to pre-press images must be input to the image-based system.
Selection of the target color profile is not always straightforward. For some printing conditions, there is no color standard that accurately represents the printed product, and compromises must be made.
Various types of target image calculation errors and their impact to print quality are dis- cussed. Methods to account for TVI compensation and plate setter linearization curves are detailed. A non-linearity arising from the conversion from CMYK to CIELAB is presented. Signal-processing methods, which facilitate control of fine detail, such as text, are also discussed.