1. An apparatus comprising: a printing device; an in-line digital capture device; and at least one controller configured to (1) receive a digital source; (2) receive a digital image of an output of the digital source printed by the printing device; (3) carry out a comparison of the digital source and the digital image to detect a given defect in the output resulting during printing of the digital source by the printing device; and (4) control an alert to either an operator or to an automatic correction mechanism based on the detected given defect, wherein the comparison comprises: registering the digital source and the digital image; applying at least one filter which is based on characteristics of the given defect to the registered digital source and digital image to form a filtered image; and comparing a function of the filtered image to a given threshold to determine presence of the given defect within the output.