An error detection apparatus and method for use with engravers, suc has gravure engravers. An error value E corresponding to the difference between a set of predetermined setup parameters and actual measurement of a portion of an engraved area on the cylinder is determined. The error value E is then used to adjust the engraver to engrave an actual cut or etch in accordance with the set of predetermined setup parameters. Advantageously, an error detection and correction system is suitable for providing a closed-loop system for engraving a cylinder. The apparatus and method may be used during initial setup or during normal operation of the engraver. Other features include an autofocus routine to facilitate the autofocus procedure. Also, image processing is further enhanced by gap filling, discontinuity removal, and light calibration methods which may be used alone, in combination with each other, or in combination with the automatic focus system and/or automatic shoe system. Other embodiments of the invention illustrate the use of a polarizing element to polarize reflected light, as well as light directed to a surface of the cylinder prior to reflection, and the use of a light emitting diode (LED) for illuminating the surface of the cylinder. The features of the improved optic system facilitate reducing or eliminating image noise, such as glare, 'blooming', inconsistent illumination, and enhances the quality of the image captured by a CCD array associated with the camera used in the imager or imaging system.