A digitizer having an illuminator with a mask configured to rotate about a central axis for reducing flare from the illuminator when digitizing a data medium having a width less than an associated length of the illuminator. A page width guide of the digitizer may be operatively coupled to the mask so that movement of the page width guide automatically rotates the mask a predetermined amount. A rare gas, external electrode, cold cathode fluorescent lamp may also be utilized as an illuminator in the digitizer.